Test Bank For Microbiology The Human Experience Second Edition John W. Foster Zarrintaj Aliabadi Jo

Chapter 01: Microbes Shape Our History LEARNING OBJECTIVES 1.1a Describe how we define a microbe, and explain why the definition is a challenge.

1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

1.1c Define viruses, and explain how they relate to living cells.

1.2a Explain how microbial diseases have changed human history.

1.2b Describe how microbes participate in human cultural practices such as production of food and drink.

1.3a Define the germ theory of disease.

1.3b Explain how Florence Nightingale first drew a statistical correlation between infectious disease and human mortality.

1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

1.3d Explain the problems in interpreting Koch’s postulates in practice.

1.4a Describe examples of how microbes contribute to natural ecosystems.

1.4b Explain how mitochondria and chloroplasts evolved by endosymbiosis.

1.5a Describe how the structure of DNA was discovered, and explain the significance of DNA for determining the traits of life.

1.5b Describe how the manipulation of DNA information has transformed the practice of medicine.

MULTIPLE CHOICE 1. Which of the following is NOT considered a beneficial product of microorganisms? a. nitrogen fixation c. synthesis of vitamins b. production of fermented foods d. causative agents of disease ANS: D DIF: Easy REF: 1.1 OBJ: 1.1a Describe how we define a microbe, and explain why the definition is a challenge.

MSC: Remembering 2. A microbe that is multicellular and photosynthetic, and has cells 50 m in size, would most likely be a(n) a. fungus. c. virus. b. E. coli. d. alga.

ANS: D DIF: Moderate REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Applying 3. In the figure shown, the organism indicated with the arrow could be a

a. virus. b. bacterium.

c. macroscopic fungus. d. large ameba.

ANS: B DIF: Easy REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Applying 4. The organism shown in the figure below is a(n)

a. virus. b. bacterium.

c. archaeon. d. eukaryote.

ANS: D DIF: Moderate REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Applying 5. Which of the following demonstrates correct scientific notation of a bacterial organism? a. Staphylococcus Epidermidis c. Staphylococcus epidermidis b. Staphylococcus epidermidis d. Staphylococcus Epidermidis ANS: C DIF: Easy REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Applying 6. The key characteristic that differentiates a prokaryote from a eukaryote is the a. absence of proteins. b. presence of DNA. c. absence of membrane-bound organelles. d. presence of a cell wall.

ANS: C DIF: Easy REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Remembering 7. Which of the following methods for classifying life forms is MOST accurate in distinguishing between two closely related rod-shaped bacterial organisms, Salmonella typhimurium and Escherichia coli? a. physical characteristics c. DNA sequence comparison b. method of reproduction d. environmental habitat ANS: C DIF: Moderate REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Applying 8. Which of the following is always classified as a eukaryote? a. papillomavirus c. Escherichia coli b. Methanocaldococcus jannaschii d. yeast ANS: D DIF: Moderate REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Understanding 9. Which of the following has been used as a tool for gene therapy? a. viruses c. protozoa b. archaea d. fungi ANS: A DIF: Easy REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Understanding 10. Which of the following would you NOT expect to find inhabiting the human digestive tract? a. archaea c. bacteria b. algae d. intestinal viruses ANS: B DIF: Moderate REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Understanding 11. Antibiotics are chemotherapeutic drugs that function by inhibiting an important cellular structure or process of an organism that is causing an infection. Which of the following would not be affected by an antibiotic that targets cellular metabolic enzymes? a. Streptococcus pyogenes bacteria b. Herpes virus c. ameba d. bread mold ANS: B DIF: Moderate REF: 1.1 OBJ: 1.1c Define viruses, and explain how they relate to living cells.

MSC: Analyzing 12. Which scientist is credited with constructing the first microscope? a. Antonie van Leeuwenhoek c. Robert Hooke b. Catherine of Siena d. Louis Pasteur ANS: C DIF: Easy REF: 1.2 OBJ: 1.2a Explain how microbial diseases have changed human history.

MSC: Remembering 13. Which of the following was an unexpected benefit of the bubonic plague? a. There was no benefit to the bubonic plague. b. The population of Europe experienced a baby boom. c. It resulted in a better understanding of aseptic practices and how to prevent the spread of infection. d. The population decline enabled the cultural advancement of the Renaissance.

ANS: D DIF: Easy REF: 1.2 OBJ: 1.2a Explain how microbial diseases have changed human history.

MSC: Understanding 14. Which of the following organisms would you NOT be able to see using Robert Hooke’s microscope? a. vinegar eels c. mold filaments b. dust mites d. Mycobacterium tuberculosis ANS: D DIF: Moderate REF: 1.2 OBJ: 1.2a Explain how microbial diseases have changed human history.

MSC: Understanding 15. Which of the following pathogens is thought to have profoundly affected societies and cultural practices throughout history? a. E. coli c. H. pylori b. Yersinia pestis d. S. pyogenes ANS: D DIF: Moderate REF: 1.2 OBJ: 1.2a Explain how microbial diseases have changed human history.

MSC: Applying 16. If Spallanzani had unknowingly poked a hole in the top of his flask of meat broth, what would this have implied about the theory of spontaneous generation? a. No growth would have occurred in the flask, refuting the theory of spontaneous generation. b. No growth would have occurred in the flask, supporting the theory of spontaneous generation. c. Growth would have occurred in the flask, refuting the theory of spontaneous generation. d. Growth would have occurred in the flask, supporting the theory of spontaneous generation.

ANS: D DIF: Difficult REF: 1.2 OBJ: 1.2b Describe how microbes participate in human cultural practices such as production of food and drink.

MSC: Applying 17. What would John Tyndall have needed to use to disprove the theory of spontaneous generation with his experiments? a. a swan-neck flask c. an autoclave b. a microscope d. organic media ANS: C DIF: Moderate REF: 1.2 OBJ: 1.2b Describe how microbes participate in human cultural practices such as production of food and drink.

MSC: Applying 18. Which of the following theories was the Miller experiment designed to test? a. the endosymbiotic origin of life

b. the idea that all the chemicals found in early Earth could have come together to form the basic components of cellular life c. spontaneous generation d. the RNA world hypothesis ANS: B DIF: Moderate REF: 1.2 OBJ: 1.2a Explain how microbial diseases have changed human history.

MSC: Understanding 19. Which tool was essential in advancing the germ theory in the 1800s? a. autoclave c. DNA analysis b. microscope d. use of penicillin ANS: B DIF: Easy REF: 1.3 OBJ: 1.3a Define the germ theory of disease.

MSC: Understanding

20. Why did fewer soldiers die from infectious disease in the winter months during the Crimean War? a. Pathogens do not multiply as quickly in colder temperatures. b. Pathogens do not multiply as quickly in wet environments. c. Soldiers have fewer close interactions with other individuals during the winter months. d. Chemical agents used to treat and prevent infections do not function effectively in warmer temperatures.

ANS: A DIF: Moderate REF: 1.3 OBJ: 1.3b Explain how Florence Nightingale first drew a statistical correlation between infectious disease and human mortality.

MSC: Applying 21. Based on the figure below, approximately what percentage of the hospitalizations in week 43 resulted in deaths?

a. 80% b. 40%

c. 20% d. 4%

ANS: D DIF: Moderate REF: 1.3 OBJ: 1.3b Explain how Florence Nightingale first drew a statistical correlation between infectious disease and human mortality.

MSC: Analyzing 22. Florence Nightingale

a. b. c. d.

was a physician and statistician. discovered that mortality rates were highest in winter months. demonstrated that infectious diseases resulted in high mortality rates. had no effect on the future of public health.

ANS: C DIF: Moderate REF: 1.3 OBJ: 1.3b Explain how Florence Nightingale first drew a statistical correlation between infectious disease and human mortality.

MSC: Remembering 23. What is the causative agent of the infectious disease used to establish Koch’s postulates? a. Streptococcus pyogenes c. Helicobacter pylori b. Bacillus anthracis d. Chlamydia trachomatis ANS: B DIF: Easy REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Remembering 24. The selection of anthrax by Robert Koch was a fortunate one because the microbe that causes it a. multiplies slowly. b. multiplies to a high concentration in the kidneys. c. is not dangerous to humans. d. can remain infective outside the body for long periods.

ANS: D DIF: Moderate REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Applying 25. The arrow in the figure shows a(n)

a. gelatin suspension. b. endospore.

c. colony. d. cell.

ANS: C DIF: Easy REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Understanding 26. The first vaccination was done to prevent a. AIDS. b. smallpox.

c. tuberculosis. d. anthrax.

ANS: B DIF: Easy REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Remembering

27. Koch’s postulates are listed below. What is their correct order?

1. Same pathogen is isolated from newly diseased host 2. Pathogen isolated from diseased host 3. Pathogen grown in pure culture 4. Pathogen introduced into healthy host—disease occurs a. 2-3-4-1 c. 3-4-2-1 b. 3-2-1-4 d. 2-4-3-1 ANS: A DIF: Moderate REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Understanding 28. Which of the following techniques is effective in creating an attenuated version of a pathogen useful for vaccinations? a. putting a liquid culture of the pathogen in the freezer b. heating an aged culture of the pathogen c. homogenizing a culture of the pathogen d. exposing a culture of the pathogen to nuclear radiation ANS: B DIF: Easy REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Understanding 29. Which of the following scientists accidently discovered penicillin? a. Howard Florey c. Ernst Chain b. Alexander Fleming d. Edward Jenner ANS: B DIF: Easy REF: 1.5 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Remembering 30. Wendell Scott a. crystallized the tobacco mosaic virus (TMV). b. purified the penicillin molecule. c. paved the way for the development of aseptic techniques. d. developed the first vaccine used on humans.

ANS: A DIF: Easy REF: 1.5 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Remembering 31. Antibiotics are produced by a. medical doctors. b. acclaimed scientific researchers.

c. microorganisms. d. the CDC.

ANS: C DIF: Moderate REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Understanding 32. What is happening in the figure shown below?

a. The mold on the right is producing a compound that inhibits the growth of the bacterial colonies on the left. b. The mold on the right is outcompeting the bacterial cells for nutrients and therefore is growing faster. c. The bacterial cells on the left are inhibiting the growth of the mold on the right. d. The mold and bacterial cells are growing in a symbiotic relationship.

ANS: A DIF: Moderate REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Applying 33. Warts are a common skin condition caused by an organism that cannot be grown in pure culture on an agar petri dish and is small enough to pass through a tiny-pored filter. The causative agent of warts is a(n) a. bacterium. c. archaea. b. virus. d. fungus.

ANS: B DIF: Moderate REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Applying 34. Thiobacillus ferrooxidans is a microorganism that gains its energy from the oxidation of ferrous iron (Fe2+) to ferric iron (Fe3+) and hydrogen sulfide (H2S) to sulfuric acid (H2SO4). Based on this information, T. ferrooxidans is an example of a(n) a. nitrogen fixer. c. endosymbiont. b. lithotroph. d. biofilm participant.

ANS: B DIF: Moderate REF: 1.4 OBJ: 1.4a Describe examples of how microbes contribute to natural ecosystems.

MSC: Applying 35. A microbial growth medium for Staphylococcus aureus is prepared with a high salt concentration to minimize the growth of many organisms that are not capable of growth in these conditions. This is an example of a. animal culture. c. pure culture. b. endosymbiosis. d. enrichment culture.

ANS: D DIF: Moderate REF: 1.4 OBJ: 1.4a Describe examples of how microbes contribute to natural ecosystems.

MSC: Applying 36. Which of the following is NOT an example of an endosymbiont?

a. b. c. d.

Bacillus anthracis spores present in the soil of cattle farms rhizobial bacteria growing in the root nodules of certain plants microorganisms in the digestive system of the cow degrading cellulose bacteria in termite intestines digesting plant polymers

ANS: A DIF: Moderate REF: 1.4 OBJ: 1.4a Describe examples of how microbes contribute to natural ecosystems.

MSC: Applying 37. Consider the figure below. The arrow pointing from cyanobacteria to plants and algae indicates that, according to the endosymbiotic origin of eukaryotic cells, cyanobacteria

a. b. c. d.

are the early evolutionary ancestors of plants and algae. merged together to form plants and algae. serve as a common source of energy for plants and algae. were internalized by early eukaryotic cells to form the chloroplast present in plants and algae.

ANS: D DIF: Difficult REF: 1.4 OBJ: 1.4b Explain how mitochondria and chloroplasts evolved by endosymbiosis.

MSC: Analyzing 38. According to the endosymbiotic origin of eukaryotic cells, respiring bacteria similar to E. coli were engulfed by cells and evolved into the a. nucleotides. c. energy-generating organelles. b. protein-producing organelles. d. waste-degrading organelles.

ANS: C DIF: Easy REF: 1.4 OBJ: 1.4b Explain how mitochondria and chloroplasts evolved by endosymbiosis.

MSC: Remembering

39. The endosymbiotic origin of eukaryotic cells explains how a. prokaryotic cells transformed into eukaryotic cells. b. eukaryotic cells evolved from viruses. c. prokaryotic cells were incorporated by pre-eukaryotes as eukaryotic organelles. d. eukaryotic cells eliminated prokaryotic cells.

ANS: C DIF: Easy REF: 1.4 OBJ: 1.4b Explain how mitochondria and chloroplasts evolved by endosymbiosis.

MSC: Remembering 40. Which of the following statements does NOT provide evidence in support of the endosymbiotic origin of eukaryotic cells? a. The DNA sequence of mitochondria is similar to the DNA sequence of respiring bacteria. b. The DNA of chloroplasts is circular like the DNA of phototrophic bacteria. c. Mitochondria are capable of free-living outside of a eukaryotic cell. d. There is a lot of sequence homology between the DNA sequences of chloroplasts and phototrophic bacteria.

ANS: C DIF: Easy REF: 1.4 OBJ: 1.4b Explain how mitochondria and chloroplasts evolved by endosymbiosis.

MSC: Understanding 41. Which of the following negative hypothetical situations could be caused by the similarity between mitochondria and bacteria? a. Vincent’s Staphylococcus skin infection cannot be treated because the only effective antibiotic has too many toxic side effects. b. Alexander suffers from myoclonic epilepsy with ragged red fibers, a mitochondrial disease. c. Lauren inherited complex I deficiency, a mitochondrial disease that inhibits her mitochondria from producing enough energy in certain organs of her body. d. Sally was born with a pyruvate decarboxylase deficiency that prevents her mitochondria from functioning properly, resulting in severe mental retardation.

ANS: A DIF: Difficult REF: 1.4 OBJ: 1.4b Explain how mitochondria and chloroplasts evolved by endosymbiosis.

MSC: Evaluating 42. The X-ray diffraction pattern in the image shown below helped determine the structure of

a. alanine. b. penicillin.

c. vitamin B12. d. deoxyribonucleic acid.

ANS: D DIF: Moderate REF: 1.5 OBJ: 1.5a Describe how the structure of DNA was discovered, and explain the significance of DNA for determining the traits of life.

MSC: Understanding 43. Which of the following is NOT one of Rosalind Franklin’s accomplishments? a. generating the X-ray diffraction pattern of the structure of DNA b. researching the structure of RNA c. determining the form of tobacco mosaic virus’s RNA chromosome d. receiving a Nobel Prize ANS: D DIF: Easy REF: 1.5 OBJ: 1.5a Describe how the structure of DNA was discovered, and explain the significance of DNA for determining the traits of life.

MSC: Remembering 44. Nobel Prize winners Watson and Crick a. generated the X-ray diffraction pattern of the structure of DNA. b. researched the structure of RNA. c. determined the form of tobacco mosaic virus’s RNA chromosome. d. proposed a structure for the complementary base pairing of DNA. ANS: D DIF: Easy REF: 1.5 OBJ: 1.5a Describe how the structure of DNA was discovered, and explain the significance of DNA for determining the traits of life.

MSC: Remembering 45. The first cellular genome sequenced was a(n) a. animal. b. virus.

c. archaea. d. bacteria.

ANS: D DIF: Easy REF: 1.5 OBJ: 1.5b Describe how the manipulation of DNA information has transformed the practice of medicine.

MSC: Remembering 46. The discovery of ________ first stimulated the funding of millions of dollars into medical research. a. penicillin c. DNA sequencing b. the structure of DNA d. vaccines ANS: A DIF: Easy REF: 1.5 OBJ: 1.5b Describe how the manipulation of DNA information has transformed the practice of medicine.

MSC: Understanding 47. CASE HISTORY In 2000, on a farm in North Dakota, 67-year-old Caleb helped bury five cows that had died of anthrax.

Wearing heavy leather gloves, Caleb placed chains around the heads and hooves of the carcasses and moved them to the burial site. Four days later, he noticed a small lump on his left cheek. Over two days, the lump enlarged and a lesion opened. Caleb then sought medical attention. The physician reported a firm, superficial nodule surrounded by a purple ring, with an overlying black eschar (piece of dead tissue sloughed from the skin). The physician prescribed ciprofloxacin, the standard antibiotic for cutaneous (affecting skin) anthrax. Testing the patient’s serum with a bacterial antigen revealed the presence of antibodies, confirming the diagnosis of anthrax. The ciprofloxacin was continued, and the patient slowly improved over several weeks.

If this scenario were an application of Koch’s postulates rather than a natural infection, which of these case notes would NOT be relevant? a. Bacillus anthracis can be isolated from lesions on all dead cows. b. Antibiotics successfully treated the lesion. c. Caleb developed a lesion similar to those affecting the dead cows. d. Bacillus anthracis can be isolated from Caleb’s lesion.

ANS: B DIF: Easy REF: Case History 1.1 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Applying COMPLETION 1. Bacteria and archaea are classified as ________.

ANS: prokaryotes DIF: Easy REF: 1.1 OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Remembering 2. In 1884, the Gram stain was devised to distinguish bacteria from ________ cells.

ANS: human DIF: Easy REF: 1.2 OBJ: 1.2a Explain how microbial diseases have changed human history.

MSC: Remembering 3. Florence Nightingale used a polar area chart to track the ________ of soldiers during the Crimean War. ANS: cause of death; mortality DIF: Moderate REF: 1.3 OBJ: 1.3b Explain how Florence Nightingale first drew a statistical correlation between infectious disease and human mortality.

MSC: Remembering 4. The involvement of bacteria in ________ explains why their presence is essential to the continued existence of plants and animals.

ANS: geochemical cycling DIF: Moderate REF: 1.4 OBJ: 1.4a Describe examples of how microbes contribute to natural ecosystems.

MSC: Understanding 5. Observe the DNA sequence shown below. This sequence terminates at the base ________.

ANS: G DIF: Easy REF: 1.5 OBJ: 1.5b Describe how the manipulation of DNA information has transformed the practice of medicine.

MSC: Analyzing SHORT ANSWER 1. Consider the statement below. Evaluate whether you agree or disagree with this statement and provide evidence supporting your position.

“Microorganisms are dangerous to human existence.”

ANS: A variety of answers are acceptable so long as they mention the positive and negative effects of microorganisms and provide appropriate evidence to support their claim.

DIF: Difficult REF: 1.1 OBJ: 1.1a Describe how we define a microbe, and explain why the definition is a challenge.

MSC: Evaluating 2. Explain how the piece of equipment shown in the image below was used to disprove the theory of spontaneous generation.

ANS: The curved shape of the neck prevented microbes in dust particles in the air from reaching the media while still allowing air to flow, demonstrating that even with oxygen, no spontaneous growth of microorganisms occurred without direct contact with dust particles from the environment.

DIF: Difficult REF: 1.2 OBJ: 1.2b Describe how microbes participate in human cultural practices such as production of food and drink.

MSC: Analyzing 3. Explain how it would have taken much longer to disprove the theory of spontaneous generation if John Tyndall was the only scientist investigating it.

ANS: John Tyndall found the opposite result of Pasteur in his experiments because material he was boiling contained endospores that were resistant to boiling. His experiments would have appeared to support the theory of spontaneous generation because microbes from the spores germinated in a sealed flask.

DIF: Difficult REF: 1.2 OBJ: 1.2b Describe how microbes participate in human cultural practices such as production of food

and drink.

MSC: Evaluating

4. Why did agar offer an improvement over gelatin for the growth of microorganisms?

ANS: Agar remains more solid at higher temperatures than does gelatin.

DIF: Easy REF: 1.3 OBJ: 1.3c Explain how Koch’s postulates can show that a specific kind of microbe causes a disease.

MSC: Remembering 5. Give an example of a situation where Koch’s postulates may not work properly.

ANS: A variety of answers are acceptable so long as they deal with one of the following: a disease-causing agent present in a host that does not cause symptoms, a disease-causing agent in which the levels of the agent are very low or difficult to detect in the host, a disease-causing agent that cannot be grown in pure culture, or a disease-causing agent for which there is no known nonhuman model.

DIF: Difficult REF: 1.3 OBJ: 1.3b Explain how Florence Nightingale first drew a statistical correlation between infectious disease and human mortality.

MSC: Evaluating 6. Why does traditional microbial growth media only allow for the growth of 0.1% of all microorganisms in pure culture in the laboratory?

ANS: Traditional microbial growth media contains nutrients that are used to feed humans. While some microorganisms can flourish in these conditions, many are much more diverse and cannot grow on these nutrients or will be outcompeted by those organisms that can.

DIF: Easy REF: 1.4 OBJ: 1.4a Describe examples of how microbes contribute to natural ecosystems.

MSC: Understanding 7. Explain how comparing the sequences of antibiotic-resistant and -sensitive Mycobacterium tuberculosis could be useful to treating tuberculosis.

ANS: The answer should discuss how this can lead to identification of the difference(s) that lead(s) to resistance and from there how to possibly target the antibiotic-resistant organism. For example: comparing the sequences of antibiotic-resistant and -sensitive Mycobacterium tuberculosis can allow one to note the differences between the two. Knowing what is missing or present in the antibioticresistant variety can allow researchers to understand how the resistant organisms are developing resistance. This is the first step toward developing a method to combat these resistant organisms.

DIF: Difficult REF: 1.5 OBJ: 1.5b Describe how the manipulation of DNA information has transformed the practice of medicine.

MSC: Evaluating 8. CASE HISTORY

Debi was an ordinary teenager attending an affluent American public high school when she contracted tuberculosis (TB). She did not know the person who infected her. Infection requires inhalation of the causative bacteria.

Debi coughed all the time, felt tired, and was losing weight. Her coughing brought up blood. An Xray revealed the signs of infection in her lung, including a large hole eaten away by the bacteria.

From Debi’s sputum sample, a DNA sequence was amplified by polymerase chain reaction (PCR).

The DNA sequence revealed Mycobacterium tuberculosis, the cause of TB. Doctors prescribed isoniazid and rifampin, antibiotics that kill most strains of M. tuberculosis. But Debi’s TB strain proved resistant to nearly all known drugs (MDR-TB).

Because drugs failed to eliminate the MDR strain, surgeons removed nearly half of her right lung to help the antibiotics overcome the infection. Debi recovered and returned to high school. She would have to continue taking antibiotics for years afterward. All the teachers and students in Debi’s school were screened, and over 200 were found to have been infected by a student with tuberculosis misdiagnosed for two years. All required treatment to prevent disease.

When Debi contracted tuberculosis, she did not know who had infected her or how she had been infected. How could this be?

ANS: The bacteria was airborne.

DIF: Moderate REF: Case History Chapter 1 Intro OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Understanding 9. CASE HISTORY Debi was an ordinary teenager attending an affluent American public high school when she contracted tuberculosis (TB). She did not know the person who infected her. Infection requires inhalation of the causative bacteria.

Debi coughed all the time, felt tired, and was losing weight. Her coughing brought up blood.

An X-ray revealed the signs of infection in her lung, including a large hole eaten away by the bacteria.

From Debi’s sputum sample, a DNA sequence was amplified by polymerase chain reaction (PCR).

The DNA sequence revealed Mycobacterium tuberculosis, the cause of TB. Doctors prescribed isoniazid and rifampin, antibiotics that kill most strains of M. tuberculosis. But Debi’s TB strain proved resistant to nearly all known drugs (MDR-TB).

Because drugs failed to eliminate the MDR strain, surgeons removed nearly half of her right lung to help the antibiotics overcome the infection. Debi recovered and returned to high school. She would have to continue taking antibiotics for years afterward. All the teachers and students in Debi’s school were screened, and over 200 were found to have been infected by a student with tuberculosis misdiagnosed for two years. All required treatment to prevent disease.

Which organism in this case history is the pathogen? To what domain does this organism belong and what are the defining features of that domain?

ANS: The pathogen should be identified as M. tuberculosis, a bacterium. Defining features that separate this group from Archaea and Eukarya should be included.

DIF: Easy REF: Case History Chapter 1 Intro OBJ: 1.1b Describe the three major domains of life: Archaea, Bacteria, and Eukarya. Explain what the three domains have in common and how they differ.

MSC: Understanding

Chapter 02: Basic Concepts of Infectious Disease LEARNING OBJECTIVES 2.1a Describe differences between microbiota and pathogens.

2.1b Discuss the relationship between infection and disease and between virulence and pathogenicity.

2.1c Differentiate between infectious dose and lethal dose.

2.1d Discuss the fundamental attributes of a successful pathogen.

2.2a Distinguish between the signs and symptoms of a disease.

2.2b Explain the role of immunopathogenesis in infectious disease.

2.2c Describe the five basic stages of an infectious disease.

2.3a Describe complex versus simple infection cycles.

2.3b Differentiate endemic, epidemic, and pandemic disease.

2.3c Explain animal reservoirs and incubators.

2.4a Describe the various portals of entry and exit for microbial pathogens.

2.4b Discuss concepts of biosafety and biocontainment.

2.5a Define the biological features of human hosts that influence the course of an infection.

2.5b Explain how host behavior can impact susceptibility to disease.

2.6a Explain how efforts to expand civilization impact emerging infectious diseases.

2.6b Explain how climate change can alter infectious disease patterns.

MULTIPLE CHOICE 1. What kind of relationship exists between microbiota and their human hosts? a. mutualistic c. endoparasitic b. pathogenic d. ectoparasitic ANS: A DIF: Easy REF: 2.1 OBJ: 2.1a Describe differences between microbiota and pathogens.

MSC: Remembering 2. This image below shows a person afflicted with athlete’s foot, which is caused by the fungus

Trichophyton rubrum. T. rubrum is an example of a(n)

a. endoparasite.

c. mutualist.

b. ectoparasite.

d. fomite.

ANS: B DIF: Moderate REF: 2.1 OBJ: 2.1a Describe differences between microbiota and pathogens.

MSC: Applying 3. The graph below shows the percent mortality in populations of lab animals exposed to

increasing concentrations of two different pathogens (agent 1 and agent 2). What is the lethal dose 50% (LD50) of agent 2?

a. 400 b. 600

c. 800 d. 1,000

ANS: B DIF: Moderate REF: 2.1 OBJ: 2.1c Differentiate between infectious dose and lethal dose.

MSC: Understanding 4. The graph below shows the percent mortality in populations of lab animals exposed to

increasing concentrations of two different pathogens (agent 1 and agent 2). Which of the following is a true statement?

a. b. c. d.

The LD50 for agent 1 is 800.

The LD50 for agent 2 is lower than that for agent 1.

Agent 1 is more virulent than agent 2.

Agent 2 is more virulent than agent 1.

ANS: C DIF: Moderate REF: 2.1 OBJ: 2.1c Differentiate between infectious dose and lethal dose.

MSC: Understanding 5. The graph below shows the percent mortality in populations of lab animals exposed to increasing concentrations of two different pathogens (agent 1 and agent 2). Which of the following is a true statement about the LD50?

a. b. c. d.

The LD50 is the number of organisms required to kill 50% of the group.

The LD50 is the number of organisms required to infect 50% of the group.

The higher the LD50 the more virulent the organism.

The LD50 is the same as the ID50.

ANS: A DIF: Moderate REF: 2.1 OBJ: 2.1c Differentiate between infectious dose and lethal dose.

MSC: Understanding 6. Which of the following is NOT a fundamental attribute of a successful pathogen? a. host attachment c. nutrient acquisition b. immune avoidance d. wide host range ANS: D DIF: Moderate REF: 2.1 OBJ: 2.1d Discuss the fundamental attributes of a successful pathogen.

MSC: Understanding 7. The image below shows a rash associated with Rocky Mountain spotted fever. This rash is an

example of a

a. sign.

c. sequelae.

b. symptom.

d. fomite.

ANS: A DIF: Moderate REF: 2.2 OBJ: 2.2a Distinguish between the signs and symptoms of a disease.

MSC: Understanding 8. A fever is an example of a a. symptom. b. sign.

c. sequelae. d. syndrome.

ANS: B DIF: Moderate REF: 2.2 OBJ: 2.2a Distinguish between the signs and symptoms of a disease.

MSC: Understanding 9. Colonization occurs during the __________ phase of an infectious disease. a. incubation c. decline b. illness d. prodromal ANS: A DIF: Moderate REF: 2.2 OBJ: 2.2c Describe the five basic stages of an infectious disease.

MSC: Applying 10. Which of the following is an example of a symptom? a. a rash b. swollen glands c. jaundice (yellow tinge to the skin) d. muscle aches ANS: D DIF: Moderate REF: 2.2 OBJ: 2.2a Distinguish between the signs and symptoms of a disease.

MSC: Applying 11. A mosquito can transmit a viral pathogen into humans. The mosquito is an example of a(n) a. fomite. c. vector. b. symptom. d. endoparasite.

ANS: C DIF: Easy REF: 2.3 OBJ: 2.3a Describe complex versus simple infection cycles.

MSC: Remembering

12. An island nation normally has low background level of cholera. After an earthquake,

sanitation is disrupted and cholera cases spike to high levels on the island but not in other areas of the world. The spike in cholera cases is an example of a(n) a. endemic disease. c. pandemic disease. b. epidemic disease. d. opportunistic infection.

ANS: B DIF: Easy REF: 2.3 OBJ: 2.3b Differentiate endemic, epidemic, and pandemic disease.

MSC: Understanding 13. Human immunodeficiency virus (HIV) spreads directly from person to person via intimate

contact. HIV exhibits a. a simple infection cycle. b. a complex infection cycle.

c. vehicle transmission. d. indirect transmission.

ANS: A DIF: Easy REF: 2.3 OBJ: 2.3a Describe complex versus simple infection cycles.

MSC: Understanding

14. Lily (who has lice) brings a comb to school for picture day. After Lily combs her hair, Leticia

asks to borrow the comb. Leticia later is diagnosed with lice. In this example, the comb is a(n) a. carrier. c. incubator. b. fomite. d. portal.

ANS: B DIF: Moderate REF: 2.3 OBJ: 2.3a Describe complex versus simple infection cycles.

MSC: Understanding

15. Adhesins are proteins on the surface of microbes. Adhesins help most with which

fundamental pathogen attribute? a. host attachment b. immune avoidance

c. nutrient acquisition d. host mortality

ANS: A DIF: Moderate REF: 2.1 OBJ: 2.1d Discuss the fundamental attributes of a successful pathogen.

MSC: Understanding 16. The acme of an infectious disease, when the symptoms are most severe, occurs during which

phase of the infection? a. incubation b. illness

c. decline d. prodromal

ANS: B DIF: Moderate REF: 2.2 OBJ: 2.2c Describe the five basic stages of an infectious disease.

MSC: Remembering 17. During which phase of an infectious disease do disease symptoms begin to subside? a. incubation c. decline b. prodromal d. convalescent ANS: C DIF: Easy REF: 2.2 OBJ: 2.2c Describe the five basic stages of an infectious disease.

MSC: Remembering 18. What factor favors an infectious disease to become pandemic instead of epidemic? a. a localized animal reservoir c. a low infectious dose 50% b. rapid mortality d. a long incubation period ANS: C DIF: Difficult REF: 2.3 OBJ: 2.3b Differentiate endemic, epidemic, and pandemic disease.

MSC: Evaluating 19. Walter defecates in the company restroom, does not wash his hands thoroughly, and then uses

the office coffeepot, transferring bacteria onto the handle of the pot. Marcia pours some coffee and then goes to her desk to eat a muffin, ingesting some of the bacteria she picked up from the coffeepot. What is the route of transmission of this infection? a. fecal-oral c. urogenital b. respiratory d. parenteral ANS: A DIF: Easy REF: 2.4 OBJ: 2.4a Describe the various portals of entry and exit for microbial pathogens.

MSC: Understanding 20. A mosquito can transmit a viral pathogen into humans. What is the mode of transmission of

the virus in this instance? a. oral b. respiratory

c. urogenital d. parenteral

ANS: D DIF: Easy REF: 2.4 OBJ: 2.4a Describe the various portals of entry and exit for microbial pathogens.

MSC: Remembering 21. The image below shows a man sneezing, leading to an aerosol of pathogens. What is the most

likely mode of transmission of these pathogens to another person?

a. fecal-oral b. respiratory

c. urogenital d. parenteral

ANS: B DIF: Easy REF: 2.4 OBJ: 2.4a Describe the various portals of entry and exit for microbial pathogens.

MSC: Understanding 22. Which of the following might be an effective means of limiting a disease spread via a

urogenital route? a. not sharing needles b. wearing condoms during sexual activity c. wearing a mask that covers the nose and mouth d. washing hands before eating ANS: B DIF: Moderate REF: 2.4 OBJ: 2.4a Describe the various portals of entry and exit for microbial pathogens.

MSC: Applying 23. Which of the following is the most effective means of limiting a disease spread via a

parenteral route? a. not sharing needles b. wearing condoms during sexual activity c. wearing a mask that covers the nose and mouth d. cooking foods thoroughly ANS: A DIF: Moderate REF: 2.4 OBJ: 2.4a Describe the various portals of entry and exit for microbial pathogens.

MSC: Applying 24. Which of the following might be an effective means of limiting a disease spread via an oral

route? a. not sharing needles b. wearing condoms during sexual activity c. checking for and removing ticks after outdoor activity d. washing hands before eating ANS: D DIF: Easy REF: 2.4 OBJ: 2.4a Describe the various portals of entry and exit for microbial pathogens.

MSC: Applying 25. The most dangerous potential bioterrorism agents have what portal of entry into the human

body? a. respiratory b. urogenital

c. parenteral d. fecal

ANS: A DIF: Easy REF: 2.4 OBJ: 2.4b Discuss concepts of biosafety and biocontainment.

MSC: Applying

26. The image below shows a researcher working in a positive-pressure suit. Such attire is

required to work with biological agents in which risk level?

a. risk group I b. risk group II

c. risk group III d. risk group IV

ANS: D DIF: Easy REF: 2.4 OBJ: 2.4b Discuss concepts of biosafety and biocontainment.

MSC: Remembering

27. Giardia lamblia, a cause of diarrhea and other gastrointestinal symptoms, is acquired from

contaminated drinking water. It can be treated with several different antimicrobial drugs. Into what risk level does G. lamblia fall? a. risk group I c. risk group III

b. risk group II

d. risk group IV

ANS: B DIF: Moderate REF: 2.4 OBJ: 2.4b Discuss concepts of biosafety and biocontainment.

MSC: Evaluating

28. What factor is most responsible for both the very young and the very old being most

susceptible to infectious diseases? a. the host genotype b. different portals of entry for pathogens c. the host immune system d. the inability of these populations to communicate symptoms to health care providers ANS: C DIF: Moderate REF: 2.5 OBJ: 2.5b Explain how host behavior can impact susceptibility to disease.

MSC: Remembering 29. The host immune response can be weakened by a. too little sleep. b. moderate exercise. c. proper nutrition. d. avoiding alcohol and drugs.

ANS: A DIF: Easy REF: 2.5 OBJ: 2.5a Define the biological features of human hosts that influence the course of an infection.

MSC: Remembering 30. Which of the following host factors can prevent disease by limiting exposure? a. too little sleep b. moderate exercise c. working in the health care field d. proper hygiene ANS: D DIF: Easy REF: 2.5 OBJ: 2.5b Explain how host behavior can impact susceptibility to disease.

MSC: Applying 31. During which phase of an infectious disease are immunopathologies most likely to first

appear? a. incubation b. invasive

c. decline d. convalescent

ANS: B DIF: Moderate REF: 2.2 OBJ: 2.2b Explain the role of immunopathogenesis in infectious disease.

MSC: Applying 32. Known diseases that rapidly increase in incidence and/or geographic range are known as a. emerging. c. zoonotic. b. reemerging. d. etiologic agents.

ANS: B DIF: Easy REF: 2.6 OBJ: 2.6a Explain how efforts to expand civilization impact emerging infectious diseases.

MSC: Remembering

33. Which number in the graph shown below corresponds to the decline phase of an infectious

disease?

a. 2 b. 3

c. 4 d. 5

ANS: C DIF: Moderate REF: 2.2 OBJ: 2.2c Describe the five basic stages of an infectious disease.

MSC: Analyzing 34. Which number in the graph shown below corresponds to the convalescence period?

a. 1 b. 3

c. 5 d. 6

ANS: D DIF: Moderate REF: 2.2 OBJ: 2.2c Describe the five basic stages of an infectious disease.

MSC: Analyzing 35. Which stage of an infectious disease does number 3 represent?

a. incubation phase b. illness phase

c. prodromal phase d. decline phase

ANS: C DIF: Moderate REF: 2.2 OBJ: 2.2c Describe the five basic stages of an infectious disease.

MSC: Analyzing 36. Infectious dose is measured by determining how many microbes are required to cause a. disease symptoms in half of an experimental group of hosts. b. death in half of an experimental group of hosts. c. disease symptoms in all of an experimental group of hosts. d. death in all of an experimental group of hosts.

ANS: A DIF: Easy REF: 2.1 OBJ: 2.1c Differentiate between infectious dose and lethal dose.

MSC: Remembering 37. The ability of a microbe to cause disease is known as a. emergence. c. pathogenicity. b. invasiveness. d. virulence.

ANS: C DIF: Easy REF: 2.1 OBJ: 2.1c Differentiate between infectious dose and lethal dose.

MSC: Remembering 38. Most likely, pathogens with a broad host range a. are highly virulent in all hosts. b. are unlikely to be zoonotic diseases. c. are less likely than narrow–host range pathogens to respond to antibiotics. d. recognize receptors that are very similar among different hosts.

ANS: D DIF: Difficult REF: 2.1 OBJ: 2.1d Discuss the fundamental attributes of a successful pathogen.

MSC: Evaluating 39. Which of the following statements is FALSE regarding climate change? a. It will not affect human disease patterns. b. It can alter insect vector distribution. c. It can foster emerging diseases. d. It can foster reemerging diseases.

ANS: A DIF: Easy REF: 2.6 OBJ: 2.6b Explain how climate change can alter infectious disease patterns.

MSC: Remembering 40. A particular virus has a high infectious dose 50% and extremely low mortality, causing only

mild symptoms. This virus has __________ infectivity and __________ virulence. a. high; high c. low; low b. high; low d. low; high ANS: C DIF: Difficult REF: 2.1 OBJ: 2.1b Discuss the relationship between infection and disease and between virulence and pathogenicity. | 2.1c Differentiate between infectious dose and lethal dose.

MSC: Analyzing 41. Francisella tularensis is a highly infectious bacterium that can be contracted via multiple

routes including inhalation. It causes severe disease but is treatable. F. tularensis falls into risk group a. I. c. III. b. II. d. IV. ANS: C DIF: Moderate REF: 2.4 OBJ: 2.4b Discuss concepts of biosafety and biocontainment.

MSC: Evaluating

42. The main way that climate change can affect infectious disease patterns is by a. causing the evolution of new animal species that can serve as hosts to emerging

pathogens. b. altering where organisms can live. c. increasing the virulence of pathogens. d. decreasing the virulence of pathogens.

ANS: B DIF: Moderate REF: 2.6 OBJ: 2.6b Explain how climate change can alter infectious disease patterns.

MSC: Analyzing 43. Which of the following is NOT a driver of emerging diseases? a. decreased human drug use b. climate change c. microbial evolution d. changing land use patterns ANS: A DIF: Moderate REF: 2.6 OBJ: 2.6a Explain how efforts to expand civilization impact emerging infectious diseases.

MSC: Understanding 44. Transplacental transmission is an example of __________ transmission. a. fecal-oral c. indirect b. vehicle d. direct ANS: D DIF: Moderate REF: 2.3 OBJ: 2.3a Describe complex versus simple infection cycles.

MSC: Applying

45. The difference between an emerging and a reemerging disease is that emerging diseases

_________, and reemerging diseases __________.

a. are of viral origin; are bacterial b. are ones for which vaccines exist; lack vaccines c. are new to humans; are known but are rapidly increasing in incidence and/or

geographic range d. evolve within humans; are of zoonotic origin ANS: C DIF: Easy REF: 2.6 OBJ: 2.6a Explain how efforts to expand civilization impact emerging infectious diseases.

MSC: Remembering 46. CASE HISTORY In 1884, Yong Ding was a 38-year-old male in Canton, located in southern China. Life was hard, but Yong Ding, a cook, still managed to support his family. As he walked to his restaurant each day, he barely noticed the small bands of rats scurrying through the streets. Disease was rampant that year; victims of the Shuyi (rat epidemic) were stacked like firewood in the streets, five bodies high in places, waiting to be taken to burial. Yong knew that the disease started as a swollen gland in the armpit that often had a black appearance (now called a bubo). He checked himself daily for these swellings and, seeing none, always felt relief. Then, one morning, he found one. Within days, Yong Ding began coughing blood as the agent (a mystery at the time) spread through his bloodstream to his lungs. Once that happened, Yong Ding knew death was not far behind. More than 60,000 died this way in what was to be the start of the Third Pandemic of bubonic plague. Yong Ding’s body was one of many lining the street that year.

We now know that the cook Yong Ding was living through the Third Epidemic of bubonic plague. We also know that the rats that scurried through the streets were infested with fleas, which carried the causative agent of the bubonic plague, Yersinia pestis. In this complex infection cycle, which organism was the vector? a. Yersinia pestis c. fleas b. rats d. humans ANS: C DIF: Easy REF: Case History 2.2 OBJ: 2.3c Explain animal reservoirs and incubators.

MSC: Applying COMPLETION 1. The ability of a microbe to attach to a body surface is known as ________.

ANS: colonization DIF: Moderate REF: 2.1 OBJ: 2.1a Describe differences between microbiota and pathogens.

MSC: Remembering 2. The graph below shows the percent mortality in populations of lab animals exposed to

increasing concentrations of two different pathogens (agent 1 and agent 2). Agent ________ is more virulent.

ANS: 1; one DIF: Moderate REF: 2.1 OBJ: 2.1b Discuss the relationship between infection and disease and between virulence and pathogenicity.

MSC: Evaluating 3. A fever is often a host response to a pathogen. As such, a fever is an example of a ________.

ANS: sign DIF: Difficult REF: 2.2 OBJ: 2.2b Explain the role of immunopathogenesis in infectious disease.

MSC: Understanding 4. The typical signs and symptoms of a disease first appear during the ________ phase of an

infectious disease.

ANS: illness DIF: Moderate REF: 2.2 OBJ: 2.2c Describe the five basic stages of an infectious disease.

MSC: Remembering 5. A disease that can spread to humans from nonhuman animals is known as a ________ disease.

ANS: zoonotic DIF: Easy REF: 2.3 MSC: Remembering

OBJ: 2.3c Explain animal reservoirs and incubators.

6. An infectious disease that rapidly increases in incidence throughout the world is known as a

________.

ANS: pandemic DIF: Easy REF: 2.3 OBJ: 2.3b Differentiate endemic, epidemic, and pandemic disease.

MSC: Remembering 7. In some parts of the world, human immunodeficiency virus is endemic. Endemic diseases

require a reservoir to serve as a source of pathogen. The reservoir for HIV is ________.

ANS: humans DIF: Moderate MSC: Applying

REF: 2.3

OBJ: 2.3c Explain animal reservoirs and incubators.

SHORT ANSWER 1. Describe the difference between an infection and a disease.

ANS:

An infection occurs any time a pathogen enters or starts to grow on a host. An infection does not necessarily lead to disease—a disruption of the normal structure or function of any body part, organ, or system that can be recognized by a characteristic set of symptoms and signs.

DIF: Moderate REF: 2.1 OBJ: 2.1b Discuss the relationship between infection and disease and between virulence and pathogenicity.

MSC: Understanding 2. Why is the lethal dose 50% easier to determine than the infectious dose 50%?

ANS:

The LD50 has a clear end point of death, so it is easy to measure. The ID50 is measured by determining how many microbes are required to cause disease symptoms in half of an experimental group of hosts. Disease symptoms may be hard to measure in nonverbal animals and may be more subjective.

DIF: Difficult REF: 2.1 OBJ: 2.1c Differentiate between infectious dose and lethal dose.

MSC: Evaluating 3. What distinguishes simple from complex infection cycles?

ANS:

In a simple infection cycle the pathogen passes directly from one individual to another. In a complex infection cycle the pathogen is not transmitted via direct contact but instead is transmitted indirectly through an intermediary such as a fomite or a vector.

DIF: Moderate REF: 2.3 OBJ: 2.3a Describe complex versus simple infection cycles.

MSC: Analyzing

4. What is the difference between a sign and a symptom?

ANS:

Signs (such as rashes) can be observed by others. Symptoms (body aches) cannot be directly observed by others but are felt by the patient.

DIF: Easy REF: 2.2 OBJ: 2.2a Distinguish between the signs and symptoms of a disease.

MSC: Remembering 5. Why do some public health departments widely spray insecticides in the spring and summer?

ANS:

Because mosquitoes and other insects often serve as pathogen vectors and reservoirs, limiting insect populations can decrease human disease incidence.

DIF: Difficult MSC: Applying

REF: 2.3

OBJ: 2.3c Explain animal reservoirs and incubators.

6. What is immunopathology?

ANS:

Immunopathology refers to disease signs and symptoms caused by the host immune system in response to the pathogen. Immunopathologies may include runny nose, fever, rash, and headache.

DIF: Moderate REF: 2.2 OBJ: 2.2b Explain the role of immunopathogenesis in infectious disease.

MSC: Understanding 7. Describe how bacterial adhesins affect the preferred entry portal of pathogens.

ANS:

To initiate a productive infection, bacteria must attach to host cells. Attachment is mediated by bacterial adhesins binding to host receptors. Different portals of entry contain different kinds of host cells with different receptors. The adhesins may only allow attachment to cells in certain portals.

DIF: Difficult REF: 2.4 OBJ: 2.4a Describe the various portals of entry and exit for microbial pathogens.

MSC: Analyzing 8. Describe how a pathogen could use an exit portal different from the portal it used to enter the

host.

ANS:

Possible answers include the following: diarrhea-causing bacteria and viruses can enter via the oral route but leave via defecation; HIV can enter via the urogenital route and leave via the parenteral route in a needle (or vice versa—enter via a needle and exit via urogenital).

DIF: Moderate REF: 2.4 OBJ: 2.4a Describe the various portals of entry and exit for microbial pathogens.

MSC: Applying 9. What distinguishes risk level III from risk level IV organisms?

ANS:

While both risk level III and risk level IV pathogens can lead to lethal diseases, level IV pathogens tend to be more virulent and lack treatment options.

DIF: Moderate REF: 2.4 OBJ: 2.4b Discuss concepts of biosafety and biocontainment.

MSC: Remembering

10. List a few host factors that can influence the course of an infection by impacting immune

status.

ANS: Host age, nutritional status, and the presence of other diseases (e.g., HIV) can all affect host immune status.

DIF: Easy REF: 2.5 OBJ: 2.5a Define the biological features of human hosts that influence the course of an infection.

MSC: Remembering 11. CASE HISTORY Brandon, a 30-year-old stockbroker living in Chicago, visited his physician’s office. When the nurse asked Brandon why he was there, he blushed and said he wanted to talk only to the physician about his problem. Once the doctor entered the room, Brandon explained he had a small round lesion on his penis. When asked about his sexual partners, Brandon initially said he was dating only one woman, but when pressed, he admitted he had been intimate with two women over the past month and one man. Upon examination, the lesion appeared to cause no pain but exuded a clear fluid. The physician quickly sent a sample of the fluid to the clinical laboratory. There the sample was found to contain highly motile, corkscrew-shaped bacteria. The diagnosis was syphilis, caused by the bacterium Treponema pallidum. Left untreated, the disease could eventually cause horrible disfiguration and death. Confident that he knew the cause, the physician gave Brandon a shot of long-acting penicillin.

What signs and/or symptoms of disease (distinguish between the two in your answer) did Brandon’s doctor note as a part of this diagnosis?

ANS: Signs include lesion and fluid exudate. Symptoms include painlessness of lesion.

DIF: Easy REF: Case History Chapter 2 Intro OBJ: 2.2a Distinguish between the signs and symptoms of a disease.

MSC: Applying 12. CASE HISTORY In 2004, three people in Boston came down with a virulent form of pneumonia. An investigation by public health officials discovered that all three worked at the same laboratory studying Francisella tularensis, a bacterium that is highly infectious (although not usually spread by person-to-person contact). Under specific conditions, the organism can be aerosolized and inhaled and cause deadly pneumonia—making it a possible bioterrorism agent. Its handling is highly restricted by U.S. Homeland Security. Scientists studying this bacterium must use extreme precautionary measures to ensure that it cannot escape the laboratory. The investigation determined that the Boston researchers had indeed contracted tularemia. The scientists appear to have handled the organism in several instances without wearing or using proper protective gear—for example, examining agar plates containing the organism outside a biosafety containment hood. From the type of disease and the laboratory procedures performed, it seemed that the victims, who all fully recovered, inhaled the organism while working with it.

When working with a Risk Group III–level organism, the scientists should have known what types of precautions to take to decrease their risk of susceptibility. What protective measures should they have used to decrease their risk of susceptibility?

ANS: Protective measures should have included a biosafety containment hood and personal protective equipment.

DIF: Moderate REF: Case History 2.3 OBJ: 2.4b Discuss concepts of biosafety and biocontainment.

MSC: Applying

Chapter 03: Observing Microbes LEARNING OBJECTIVES 3.1a Explain how magnification improves resolution of a microscopic image.

3.1b Explain what can be learned from different kinds of microscopy.

3.2a Explain how light interacts with an object.

3.2b Describe how refraction enables magnification, and explain the limits to magnification and resolution.

3.3a Explain the use of a bright-field microscope.

3.3b Describe how to observe an object in focus by using a compound microscope.

3.4a Explain how a stain reveals additional information about a microscopic object.

3.4b Describe how the Gram stain distinguishes two classes of bacteria.

3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.

3.5b Describe how electron microscopy enables visualization of objects below the resolution limit of light, such as viruses and parts of cells.

MULTIPLE CHOICE 1. Resolution is a. the ability to detect individual cells. b. using a microscope to be seen. c. increasing the size of an image. d. the smallest distance two objects can be separated and still be distinguished.

ANS: D DIF: Easy REF: 3.1 OBJ: 3.1a Explain how magnification improves resolution of a microscopic image.

MSC: Remembering 2. Which of the following equals one millimeter? a. 10−3 m c. 10−9 m −6 b. 10 m d. 10−12 m ANS: A DIF: Easy REF: 3.1 OBJ: 3.1a Explain how magnification improves resolution of a microscopic image.

MSC: Remembering 3. Which of the following statements is INCORRECT? a. In fluorescence microscopy, fluorescent-labeled cellular structures are identified. b. In light microscopy, the object appears light against a dark background. c. In phase-contrast microscopy, organelles appear as light/dark patterns by variation in refractive indexes. d. Electron microscopy uses electrons to visualize the specimen.

ANS: B DIF: Moderate REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Analyzing 4. In a compound microscope, which is the accurate pathway of light?

a. b. c. d.

light source, condenser, objective, specimen, eyepiece condenser, light source, eyepiece, specimen, objective eyepiece, objective, specimen, condenser, light source light source, condenser, specimen, objective, eyepiece

ANS: D DIF: Easy REF: 3.3 OBJ: 3.3a Explain the use of a bright-field microscope.

MSC: Remembering

5. A(n) __________ microscope is used to observe specific fluorescent-labeled structures. a. compound light c. fluorescence b. phase-contrast d. electron ANS: C DIF: Easy REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Remembering 6. In order to view viruses, a(n) __________ microscope must be used. a. compound light c. fluorescence b. phase-contrast d. electron ANS: D DIF: Easy REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Remembering 7. A(n) __________ microscope is used to observe internal organelle structures. a. compound light c. fluorescence b. phase-contrast d. electron ANS: B DIF: Easy REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Remembering 8. What is the total magnification of a specimen viewed with a 10x ocular lens and a 35x objective lens? a. 10x c. 350x b. 3.5x d. 3,500x ANS: C DIF: Moderate REF: 3.3 OBJ: 3.3b Describe how to observe an object in focus by using a compound microscope.

MSC: Applying 9. In the figure below, line “B” points to the microscope’s

a. ocular lens.

c. condenser.

b. objective.

d. light source.

ANS: B DIF: Easy REF: 3.3 OBJ: 3.3b Describe how to observe an object in focus by using a compound microscope.

MSC: Remembering 10. In the figure below, line “C” points to the microscope’s

a. ocular lens. b. objective.

c. condenser. d. light source.

ANS: C DIF: Easy REF: 3.3 OBJ: 3.3b Describe how to observe an object in focus by using a compound microscope.

MSC: Remembering 11. In the figure below, line “D” points to the microscope’s

a. ocular lens. b. objective.

c. condenser. d. light source.

ANS: D DIF: Easy REF: 3.3 OBJ: 3.3b Describe how to observe an object in focus by using a compound microscope.

MSC: Remembering 12. A researcher is performing a Gram stain to differentiate between Gram-positive and Gram-negative bacteria. At the end of the procedure, a Gram-positive cell will appear a. purple. c. pink. b. colorless. d. blue.

ANS: A DIF: Easy REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Understanding 13. A researcher completes a Gram stain on Gram-positive bacteria; however, they over-decolorize the sample. What color will their bacteria be at this point? a. purple c. pink b. colorless d. blue ANS: C DIF: Difficult REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Analyzing 14. Which of the following is the correct order of the Gram-stain regents? a. iodine, crystal violet, safranin, ethanol b. ethanol, crystal violet, safranin, iodine c. crystal violet, ethanol, iodine, safranin d. crystal violet, iodine, ethanol, safranin ANS: D DIF: Moderate REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Applying 15. In Gram-negative cells, which layer is disrupted by the decolorizer in the Gram-staining procedure? a. techoic acids c. peptidoglycan b. outer membrane d. mycolic acid ANS: B DIF: Moderate REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Understanding 16. A researcher performing a Gram stain on Gram-positive bacteria stops after the addition of the mordant. What is the appearance of the bacteria at this point? a. purple c. pink b. colorless d. blue ANS: A DIF: Moderate REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Understanding 17. A researcher performing a Gram stain on Gram-positive bacteria stops after the addition of the counterstain. What is the appearance of the bacteria at this point? a. purple c. pink b. colorless d. blue ANS: A DIF: Moderate REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Understanding 18. The purpose of fixation in a staining procedure is to a. preserve the organisms. b. adhere bacterial cells to the slide. c. impart color to the sample. d. heat the sample.

ANS: B DIF: Easy REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Remembering

19. The cell wall of Gram-positive bacteria contain(s) a. a single layer of peptidoglycan. b. multiple layers of lipopolysaccharides. c. a thinner and more porous cell wall than Gram-negative species. d. multiple layers of peptidoglycan.

ANS: D DIF: Easy REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Remembering 20. Which of the following is FALSE about a properly completed Gram stain? a. It is a key tool used in the identification of bacterial species. b. It is reliable only for fresh cultures. c. It differentiates bacteria based on their cell wall components. d. At the completion of the stain, Gram-negative cells stain purple.

ANS: D DIF: Easy REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Understanding 21. Assume you stain Bacillus with malachite green with heat and then counterstain. What type of stain would you be performing? a. a differential and endospore stain b. a differential and Gram stain c. a simple and endospore stain d. a simple and Gram stain ANS: A DIF: Easy REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Remembering 22. Assume you stain Bacillus with malachite green with heat and then counterstain. After this procedure, when viewing through a microscope, the structures that appear green are a. cell walls. c. endospores. b. capsules. d. bacteria.

ANS: C DIF: Easy REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Understanding 23. A researcher is observing a bacterial specimen on the 100x objective but has forgotten to put the immersion oil on the slide. The specimen will appear a. smaller with better resolution. b. larger with poor resolution. c. somewhat fuzzy with poor resolution. d. the same.

ANS: C DIF: Moderate REF: 3.3 OBJ: 3.3b Describe how to observe an object in focus by using a compound microscope.

MSC: Understanding 24. The purpose of the condenser is to a. focus light rays onto the slide. b. magnify the image from the objective lens.

c. decrease the refractive index. d. improve the intensity of light.

ANS: A DIF: Easy REF: 3.3 OBJ: 3.3a Explain the use of a bright-field microscope.

MSC: Remembering

25. Which of the following is INCORRECT? a. Congo red is a negative stain. b. Malachite green is an acid-fast stain. c. Methylene blue is a simple stain. d. Fluorophore is an antibody stain.

ANS: B DIF: Difficult REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Analyzing 26. What are the steps of simple staining in the correct order? a. heat fix, stain with dye, rinse, blot b. rinse, blot, heat fix, stain with dye c. stain with dye, rinse, blot, heat fix d. heat fix, stain with dye, blot, rinse ANS: A DIF: Moderate REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Understanding 27. A(n) ________ microscopy microscope produces halos of bright light against a dark field. a. compound light c. fluorescence b. electron d. dark-field ANS: D DIF: Easy REF: 3.5 OBJ: 3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.

MSC: Remembering 28. A(n) ________ microscope is powerful enough to visualize ribosomes. a. compound light c. fluorescence b. electron d. dark-field ANS: B DIF: Easy REF: 3.5 OBJ: 3.5b Describe how electron microscopy enables visualization of objects below the resolution limit of light, such as viruses and parts of cells.

MSC: Remembering 29. Which of the following is FALSE concerning dark-field microscopy? a. Contamination in the medium can scatter light. b. It can be used to identify spirochetes. c. Images are dark against a light background. d. High resolution cannot be achieved.

ANS: C DIF: Moderate REF: 3.5 OBJ: 3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.

MSC: Understanding 30. An advantage of fluorescence microscopy is that it a. allows for the preservation of the specimen. b. provides the greatest resolution. c. can only stain dead specimens.

d. has the ability to detect specific microbes.

ANS: D DIF: Easy REF: 3.5 OBJ: 3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.

MSC: Remembering 31. Which of the images below shows Giardia lamblia visualized with a scanning electron microscope?

a. 1 b. 2

c. 3 d. 4

ANS: C DIF: Moderate REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Understanding 32. Which images below display organelles?

a. 1 and 2 b. 2 and 4

c. 1 and 3 d. 3 and 4

ANS: B DIF: Moderate REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Applying 33. A(n) ________ microscope best allows the observation of internal cell structures in a natural state.

a. compound light b. phase-contrast

c. dark-field d. electron

ANS: B DIF: Moderate REF: 3.5 OBJ: 3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.

MSC: Understanding 34. Which of the following statements is correct? a. Safranin is a primary stain. b. Iodine is a counterstain. c. Ethanol is a decolorizer. d. Crystal violet is a mordant.

ANS: C DIF: Moderate REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Understanding 35. If a microbiologist forgot to heat-fix a bacterial smear before staining, what would probably happen? a. Bacteria would wash off the slide. b. The stain would not stick to the bacteria. c. The bacteria would decolorize too quickly. d. The color of the stain would be too dark to see the bacteria.

ANS: A DIF: Moderate REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Understanding 36. The presence of a capsule is clinically significant because it protects the bacterial cell from a. a lack of nutrients. b. engulfment by white blood cells. c. heat. d. the staining regents.

ANS: B DIF: Moderate REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Understanding 37. Which of the figures below depicts cocci in chains?

a. 1 b. 2

c. 3 d. None of these figures.

ANS: C DIF: Easy REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Understanding 38. Which of the figures below depicts bacilli?

a. 1 b. 2

c. 3 d. None of these figures.

ANS: A DIF: Easy REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Understanding 39. Which of the figures below depicts spirochetes?

a. 1 b. 2

c. 3 d. None of these figures.

ANS: B DIF: Easy REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Understanding 40. A(n) ________ stain would be the MOST useful in helping clinicians decide which class of antibiotics to prescribe. a. negative c. endospore b. simple d. Gram ANS: D DIF: Difficult REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Analyzing 41. Which of the following is mismatched? a. dark-field microscopy—uses visible light b. fluorescence microscopy—uses a fluorescent light c. scanning electron microscopy—produces a three-dimensional image d. compound light microscopy—produces a light image against a dark background ANS: B DIF: Difficult REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Analyzing 42. A(n) ________ microscope uses variations in refractive indexes to display specimens. a. bright-field c. phase-contrast b. fluorescence d. transmission electron ANS: C DIF: Easy REF: 3.5 OBJ: 3.5b Describe how electron microscopy enables visualization of objects below the resolution limit of light, such as viruses and parts of cells.

MSC: Applying

43. In the Gram stain, which step is MOST critical in differentiating Gram-positive from Gram-negative cells? a. crystal violet c. mordant b. safranin d. ethanol ANS: D DIF: Moderate REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Analyzing 44. Which microscope technique is best for visualizing the surface structures of cells and viruses? a. phase-contrast c. scanning electron b. bright-field d. dark-field ANS: C DIF: Moderate REF: 3.5 OBJ: 3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.

MSC: Understanding 45. Which of the following statements about the Gram stain is MOST correct? a. Crystal violet differentially stains Gram-positive cells. b. Gram’s iodine differentially stains Gram-positive cells. c. Ethanol differentially stains Gram-negative cells. d. Safranin differentially stains Gram-negative cells.

ANS: C DIF: Difficult REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Analyzing 46. Oil immersion is used in which type of microscopy and on which objective? a. bright-field microscopy, 40X c. dark-field microscopy, 40x b. bright-field microscopy, 100x d. dark-field microscopy, 100x ANS: B DIF: Easy REF: 3.3 OBJ: 3.3b Describe how to observe an object in focus by using a compound microscope.

MSC: Remembering 47. Which of the images below depicts the refraction of light?

a. 1 b. 2

c. 3 d. 4

ANS: C DIF: Moderate REF: 3.2 OBJ: 3.2a Explain how light interacts with an object.

MSC: Applying

48. Which of the images below depicts the absorption of light?

a. 1 b. 2

c. 3 d. 4

ANS: A DIF: Moderate REF: 3.2 OBJ: 3.2a Explain how light interacts with an object.

MSC: Applying

49. The bending of light as it enters a substance that slows its speed is known as a. reflection. c. absorption. b. refraction. d. scattering.

ANS: B DIF: Moderate REF: 3.2 OBJ: 3.2b Describe how refraction enables magnification, and explain the limits to magnification and resolution.

MSC: Remembering 50. CASE HISTORY Jared, a 48-year-old, previously healthy man, was admitted to a hospital in Columbus, Ohio, after six days of increasing dyspnea (shortness of breath) and watery diarrhea. Jared also complained of a dry cough, myalgia (muscle pain), nausea, and vomiting. He appeared flushed and had dry mucous membranes. His temperature was 39C (102.2F), and his pulse rate was 103 beats per minute. Chest radiographs showed pneumonia with consolidation (formation of a firm mass) of the left lower lobe.

His c-reactive protein (crP, a blood protein produced by the liver) was greater than 220 milligrams per liter (mg/l), a high level that indicates inflammation.

Before onset of symptoms, Jared recalled having cleaned the filter of an outdoor whirlpool spa.

Culture from Jared’s sputum and from the spa filter revealed Gram-negative bacilli consistent with Legionella pneumophila. The diagnosis was confirmed by fluorescence microscopy using direct fluorescent antibody (DFA) stain. The patient received intravenous amoxicillin and clarithromycin antibiotics for eight days before his condition returned to normal.

If the technician conducting the Gram stain in this case study had left ethanol on the prepared slide longer than necessary, what might have been the effect on this slide and identification? a. The bacteria on the slide may have been decolorized Gram-positive bacilli. b. None. The timing of ethanol does not affect the outcome of a Gram stain. c. None. Because the bacteria appear Gram negative, they could not have been overdecolorized. d. The bacteria on the slide may have been cocci rather than bacilli.

ANS: C DIF: Moderate REF: Case History 3.2 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Analyzing

COMPLETION 1. A ________ is the only way to observe live specimens.

ANS: wet mount DIF: Moderate REF: 3.3 MSC: Remembering

OBJ: 3.3a Explain the use of a bright-field microscope.

2. In an acid-fast stain, carbolfuchsin specifically stains ________ of Mycobaterium tuberculosis.

ANS: mycolic acid DIF: Easy REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Remembering 3. Bacteria that grow as rods are commonly referred to as ________, whereas bacteria that grow as spheres are known as ________.

ANS: bacilli; cocci DIF: Easy REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Remembering 4. Refraction occurs by the ________ of light and is the key property enabling a lens to magnify an image.

ANS: bending DIF: Easy REF: 3.2 MSC: Remembering

OBJ: 3.2a Explain how light interacts with an object.

5. Using a compound microscope, the image is magnified at the ________.

ANS: objective lens and ocular lens; ocular lens and objective lens; ocular and objective lenses DIF: Easy REF: 3.3 OBJ: 3.3b Describe how to observe an object in focus by using a compound microscope.

MSC: Understanding 6. Electron microscopy uses beams of ________ to generate high-resolution images.

ANS: electrons DIF: Easy REF: 3.5 OBJ: 3.5b Describe how electron microscopy enables visualization of objects below the resolution limit of light, such as viruses and parts of cells.

MSC: Remembering 7. Immersion oil is used with the ________ objective.

ANS: 100x DIF: Easy REF: 3.3 OBJ: 3.3b Describe how to observe an object in focus by using a compound microscope.

MSC: Remembering 8. 1mm = ________ m ANS: 0.001; 10 −3 DIF: Easy REF: 3.1 OBJ: 3.1a Explain how magnification improves resolution of a microscopic image.

MSC: Remembering 9. Magnification without increase in resolution is called ________.

ANS: empty magnification DIF: Easy REF: 3.2 OBJ: 3.2b Describe how refraction enables magnification, and explain the limits to magnification and resolution.

MSC: Remembering SHORT ANSWER 1. What is the difference between a simple and a differential stain? Give one example of a simple stain and one example of a differential stain.

ANS: A simple stain uses one dye and does not impart color to other tissue or the background. A differential stain, on the other hand, differentiates between objects by staining only particular types of cells or specific subcellular structures and often stains two cells differently.

An example of a simple stain is methylene blue or crystal violet.

An example of a differential stain is the Gram stain or acid-fast stain.

DIF: Moderate REF: 3.4 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Understanding 2. What is the purpose of the mordant in the Gram-stain procedure?

ANS: The iodine solution used in the Gram stain contains iodine ions. These ions bind to the crystal violet trapped inside the bacterial cells. This is held more tightly within the cell wall and resists decolorization by the alcohol solution.

DIF: Moderate REF: 3.4 OBJ: 3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC: Applying 3. The size at which objects become visible depends on the resolution of the observer’s eye. Typically, eagles can resolve objects much smaller or farther away than humans can. Explain why.

ANS:

Resolution is achieved by focusing an image on the photoreceptors in the retina of the eye. The retinas of eagles have more tightly packed photoreceptors than those of humans, and so an eagle’s eye can resolve objects smaller or farther away than the human eye can.

DIF: Difficult REF: 3.1 OBJ: 3.1b Explain what can be learned from different kinds of microscopy.

MSC: Applying 4. Compare and contrast dark-field, phase-contrast, and fluorescence microscopy.

ANS: Dark-field, phase-contrast, and fluorescence microscopy are all types of light microscopy. Dark-field uses a special condenser that blocks out transmitted light from the specimen; therefore, the image appears light against a black background. Phase-contrast also uses light; however, because of the high concentration of solutes, the light is refracted differently throughout the cell. Fluorescence microscopy allows the visualization of specific cellular molecules within the sample. Visible light is used along with fluorescent dyes, which stain the specimen. These fluorophores are excited with different wavelengths of light and emit colors.

DIF: Difficult REF: 3.5 OBJ: 3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.

MSC: Analyzing 5. Label the figure below with different interactions of light with matter. Please describe what is happening with each interaction.

ANS: 1. Absorption: Label light wave and heat increasing. Description: Absorption occurs when the energy is acquired or absorbed by the object. Energy is converted to heat.

2. Reflection: Label light waves with incident angle and angle of reflection. Description: Reflection occurs when the wave bounces off the surface at an angle equal to its incident angle.

3. Refraction: Label the light waves. Description: Refraction is the bending of light as it enters a substance that slows its speed. Refraction is the key property that enables a lens to magnify an image.

4. Scattering: Label the light waves. Description: Scattering occurs when a portion of the wave front is converted to a spherical wave originating from the object. If many particles simultaneously scatter light, a haze is observed.

DIF: Difficult MSC: Analyzing

REF: 3.2

OBJ: 3.2a Explain how light interacts with an object.

6. CASE HISTORY Marianna and Julio, two children in Oklahoma aged 8 and 11, fell ill with food poisoning after consuming commercially canned hot dog chili sauce. The children complained of double vision and an inability to move their facial muscles.

Examination showed normal vital signs, symmetrical weakness (equal on right and left sides), and fixed pupils due to cranial nerve palsy (paralysis). Upper-body paralysis gradually spread downward, and breathing became labored.

Botulinum toxin was identified in their blood by fluorescent monoclonal antibodies (antibodies produced by a genetically uniform cell culture).

The children were placed on mechanical ventilation (a machine that assists breathing) and treated with botulinum antitoxin. After several days, the children were removed from mechanical ventilation.

They underwent physical rehabilitation for a full recovery.

The chili sauce was traced to a canning facility where six swollen cans tested positive for botulinum toxin A. From the cans, inspectors cultured a bacterium that grew only without oxygen, as in a closed can. A microscope showed that the bacterium had a distinctive club-shaped appearance.

The bacterium was Clostridium botulinum, which produces botulinum toxin, the cause of botulism.

One end of the club-shaped cell contains an endospore, an inert form of the cell that can germinate and grow in a closed container of food. Growing cells produce botulinum toxin, leading to botulism, a life-threatening form of paralysis. Microscopy of the pathogen’s unique form confirms the identification.

Why was fluorescence microscopy used to help identify the causative agent of the children’s disease, rather than bright-field?

ANS: Both antibodies and toxin are too small to be visualized in bright-field; however, no fluorescence would be detected in the absence of toxin using the method provided in the case study. If bacteria had been present these could have been visualized in bright-field.

DIF: Difficult REF: Case History Chapter 3 Intro OBJ: 3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.

MSC: Evaluating 7. CASE HISTORY Purna, a six-year-old boy in India’s state of Assam, fell ill with fever. At the time, prolonged rainfall had left vast pools of water, breeding mosquitoes. First the boy felt intense chills, and his temperature rose to 40 C (104 F). He experienced nausea and intense headaches and vomited repeatedly. The fever subsided, only to return three days later. After several weeks of cycling fevers, Purna was at last brought to a clinic for examination. He showed extreme anemia, with enlarged spleen and liver. A blood film slide revealed Plasmodium falciparum, a parasite that causes malaria. In the Assam outbreak of malaria, 400,000 people were infected. Some travelers who returned to the United States experienced malarial symptoms months afterward.

Explain the role of fixation and staining in the use of microscopy to identify malaria infection.

ANS: Fixation kills the cells and stabilizes the sample on a slide. In fixation, cells are made to adhere to a slide in a fixed position. The Giemsa stain contains eosin, a negatively charged dye that binds red blood cells, and methylene blue, a positively charged dye that binds the negatively charged phosphate groups of DNA. The methylene blue specifically stains the DNA-containing nucleus of the malarial parasite. Giemsa stain reveals both the “ring form” stage of the parasite, growing within a red blood cell, and the “gametocyte” stage that develops outside the host cell, ready for transmission to the next host.

DIF: Difficult REF: Case History 3.2 OBJ: 3.4a Explain how a stain reveals additional information about a microscopic object.

MSC: Applying

Chapter 04: Living Chemistry: From Atoms to Cells LEARNING OBJECTIVES 4.1a Describe how atoms form the molecules of life.

4.1b Describe the types of bonds atoms can form to make a molecule.

4.1c Explain the special properties of the water molecule, and distinguish between hydrophilic and hydrophobic molecules.

4.2a Describe organic molecules, and explain the role of functional groups and the formation of macromolecules.

4.2b Describe the structure of lipids and their key functions within a cell.

4.2c Describe the structure of sugars and polysaccharides.

4.3a Describe the structure of DNA, and explain how DNA stores information in its sequence of base pairs.

4.3b Describe the structure and diverse functions of RNA. 4.3c Describe the fundamental structure of proteins.

4.4a Explain how energy and entropy determine the direction of reactions.

4.4b Describe the oxidation-reduction changes that occur during reactions.

4.4c Explain how enzymes catalyze reactions and how various factors influence the rate of reaction.

4.5a Describe the structure of cellular membranes.

4.5b Explain the concept of selective permeability of a membrane.

4.5c Explain how membranes compartmentalize cells and control the movement of a cell’s molecules.

4.5d Describe the effect of osmosis on cells.

4.6a Describe how endocytosis and phagocytosis transport material into a eukaryotic cell.

4.6b Explain how pathogens take advantage of endocytosis and phagocytosis.

MULTIPLE CHOICE 1. Which bond type is the strongest in the aqueous cytoplasm of a cell? a. covalent c. hydrophobic b. hydrogen d. ionic ANS: A DIF: Moderate REF: 4.1 OBJ: 4.1b Describe the types of bonds atoms can form to make a molecule.

MSC: Applying 2. An ionic bond a. involves the sharing of electrons. b. involves the gaining or losing of electrons. c. forms between the H atom and O atoms in water molecules. d. is weaker than a hydrogen bond.

ANS: B DIF: Moderate REF: 4.1 OBJ: 4.1b Describe the types of bonds atoms can form to make a molecule.

MSC: Remembering 3. Molecules with which kinds of bonds are hydrophobic? a. hydrogen c. nonpolar covalent b. ionic d. polar covalent

ANS: C DIF: Moderate REF: 4.1 OBJ: 4.1c Explain the special properties of the water molecule, and distinguish between hydrophilic and hydrophobic molecules.

MSC: Applying 4. Which arrow in the figure below is drawn to a hydrogen atom that can form a hydrogen bond with water?

a. A b. B

c. C d. D

ANS: A DIF: Moderate REF: 4.1 OBJ: 4.1c Explain the special properties of the water molecule, and distinguish between hydrophilic and hydrophobic molecules.

MSC: Applying 5. Molecules that are soluble in water are ________ and molecules that are insoluble in water are ________. a. endergonic; exergonic b. nonpolar; polar c. hydrophobic; hydrophilic d. hydrophilic; hydrophobic ANS: D DIF: Easy REF: 4.1 OBJ: 4.1c Explain the special properties of the water molecule, and distinguish between hydrophilic and hydrophobic molecules.

MSC: Remembering 6. Which of the following is NOT true of the properties of water? a. Water is a solvent. b. The hydrogen bonding contributes to water’s ability to support life. c. Water dissolves non-polar compounds. d. Hydrogen bonds are short-lived and constantly forming and breaking.

ANS: C DIF: Moderate REF: 4.1 OBJ: 4.1c Explain the special properties of the water molecule, and distinguish between hydrophilic and hydrophobic molecules.

MSC: Understanding 7. Which of the following molecular formulas might be of an organic molecule?

a. H2O b. C2H4O

c. CO2 d. NH3

ANS: B DIF: Moderate REF: 4.2 OBJ: 4.2a Describe organic molecules, and explain the role of functional groups and the formation of macromolecules.

MSC: Applying 8. The cellular molecule shown below is a(n)

a. lipid. b. amino acid.

c. ribonucleic acid. d. protein.

ANS: A DIF: Moderate REF: 4.2 OBJ: 4.2b Describe the structure of lipids and their key functions within a cell.

MSC: Understanding 9. A cellular function of lipids is a. catalysis. b. information storage.

c. compartmentalization. d. sugar production.

ANS: C DIF: Difficult REF: 4.2 OBJ: 4.2b Describe the structure of lipids and their key functions within a cell.

MSC: Understanding 10. Which of the following is true of glycerol? a. It is hydrophobic. b. It is a component of proteins. c. It contains three amino groups. d. It contains three hydroxyl groups.

ANS: D DIF: Difficult REF: 4.2 OBJ: 4.2b Describe the structure of lipids and their key functions within a cell.

MSC: Applying 11. Which of the following is true of saturated fats? a. Their carbon-carbon bonds are all single bonds. b. They remain fluid at room temperature. c. They may contain one or more double bonds between adjacent carbon molecules. d. Monosaturated fats have one or more double bonds between adjacent carbon molecules.

ANS: A DIF: Difficult REF: 4.2 OBJ: 4.2b Describe the structure of lipids and their key functions within a cell.

MSC: Applying 12. Both lipids and sugars a. store energy. b. are hydrophobic.

c. are hydrophilic. d. contain nitrogen.

ANS: A DIF: Difficult REF: 4.2 OBJ: 4.2a Describe organic molecules, and explain the role of functional groups and the formation of macromolecules.

MSC: Evaluating 13. The cellular molecule shown below is a(n)

a. amino acid. b. glycerol.

c. lipid. d. sugar.

ANS: D DIF: Moderate REF: 4.2 OBJ: 4.2c Describe the structure of sugars and polysaccharides.

MSC: Understanding 14. Which of the following is true of glucose? a. It is a component of DNA and RNA. b. It can form a ring structure. c. It contains numerous amino groups. d. It is a five-carbon sugar.

ANS: B DIF: Moderate REF: 4.2 OBJ: 4.2c Describe the structure of sugars and polysaccharides.

MSC: Understanding 15. Polysaccharides are a polymer of what kind of monomer? a. amino acids c. lipids b. deoxyribonucleotides d. sugars ANS: D DIF: Easy REF: 4.2 OBJ: 4.2c Describe the structure of sugars and polysaccharides.

MSC: Remembering 16. What organic molecule is shown below?

a. a sugar b. an amino acid

c. a nucleotide d. a nucleic acid

ANS: C DIF: Moderate REF: 4.3 OBJ: 4.3a Describe the structure of DNA, and explain how DNA stores information in its sequence of base pairs.

MSC: Remembering 17. DNA is synthesized by enzymes that use __________ as substrates. a. NTPs c. NDPs b. dNTPs d. dNDPs ANS: B DIF: Moderate REF: 4.3 OBJ: 4.3a Describe the structure of DNA, and explain how DNA stores information in its sequence of base pairs.

MSC: Understanding 18. The enzyme commonly used in PCR, Taq polymerase, synthesizes what macromolecule? a. DNA c. proteins b. RNA d. polysaccharides ANS: A DIF: Easy REF: 4.3 OBJ: 4.3a Describe the structure of DNA, and explain how DNA stores information in its sequence of base pairs.

MSC: Understanding 19. A cell’s genome consists of 20% thymine. What is the percentage of cytosine? a. 20% c. 60% b. 30% d. 80% ANS: B DIF: Difficult REF: 4.3 OBJ: 4.3a Describe the structure of DNA, and explain how DNA stores information in its sequence of base pairs.

MSC: Applying 20. An infectious agent remains infectious after treatment with an enzyme that destroys DNA. The infectious agent might be a(n) a. archaeal cell. c. eukaryote. b. bacteria. d. virus.

ANS: D DIF: Difficult REF: 4.3 OBJ: 4.3b Describe the structure and diverse functions of RNA. MSC: Evaluating 21. The molecule shown below is a(n)

a. amino acid. b. monosaccharide.

c. deoxyribonucleotide. d. ribonucleotide.

ANS: A DIF: Easy REF: 4.3 OBJ: 4.3c Describe the fundamental structure of proteins.

MSC: Remembering

22. Regular, repeating patterns over short regions of a protein are known as the protein’s ________ structure. a. primary c. tertiary b. secondary d. quaternary ANS: B DIF: Moderate REF: 4.3 OBJ: 4.3c Describe the fundamental structure of proteins.

MSC: Remembering

23. All of the following are true of hydrogen bonding EXCEPT that a. beta sheets are formed from extensive hydrogen bonding. b. hydrogen bonds are the strongest type of bonds. c. hydrogen bonds stabilize the tertiary structure. d. hydrogen bonds are absent in the primary structure.

ANS: B DIF: Moderate REF: 4.3 OBJ: 4.3c Describe the fundamental structure of proteins.

MSC: Remembering

24. In the model of a cellular macromolecule below, spirals represent alpha helices and arrows represent beta sheets. What does the model represent?

a. an amino acid b. a protein ANS: B

c. a ribonucleic acid d. a polysaccharide DIF: Easy

REF: 4.3

OBJ: 4.3c Describe the fundamental structure of proteins.

MSC: Applying

25. A molecule of ATP undergoes hydrolysis yielding AMP and two molecules of phosphate. Which of the following is true of this reaction? a. The entropy has decreased. b. The change in free energy, G, is positive. c. The change in free energy, G, is negative. d. The reaction is endergonic.

ANS: C DIF: Moderate REF: 4.4 OBJ: 4.4a Explain how energy and entropy determine the direction of reactions.

MSC: Analyzing 26. Which of the following statements accurately describes the relationship between G and Keq? a. There is no relationship, as they are independent entities. b. When Keq is greater than 1, G is negative. c. When Keq is greater than 1, G is positive. d. When Keq is less than 1, G is negative.

ANS: B DIF: Moderate REF: 4.4 OBJ: 4.4a Explain how energy and entropy determine the direction of reactions.

MSC: Understanding 27. In a reaction where substrates A and B combine to form products C and D (A+B yields C+D), which of the following could drive the reaction to the right toward products? a. decreasing the concentration of A c. increasing the concentration of C b. decreasing the concentration of B d. decreasing the concentration of D ANS: D DIF: Difficult REF: 4.4 OBJ: 4.4a Explain how energy and entropy determine the direction of reactions.

MSC: Evaluating 28. The second law of thermodynamics states that a. energy is neither created nor destroyed. b. matter is neither created nor destroyed. c. in energy transformations, disorder tends to increase. d. in energy transformations, disorder tends to decrease.

ANS: C DIF: Easy REF: 4.4 OBJ: 4.4a Explain how energy and entropy determine the direction of reactions.

MSC: Understanding 29. A reaction with a positive G and low activation energy will be a. spontaneous and slow. c. endergonic and fast. b. exergonic and fast. d. endergonic and slow.

ANS: C DIF: Difficult REF: 4.4 OBJ: 4.4c Explain how enzymes catalyze reactions and how various factors influence the rate of reaction.

MSC: Analyzing 30. The most typical way for a cell to increase the rate of a reaction is by a. increasing the cell’s temperature. c. decreasing the cell’s pH. b. increasing the cell’s pH. d. using an enzyme.

ANS: D

DIF: Easy

REF: 4.4

OBJ: 4.4c Explain how enzymes catalyze reactions and how various factors influence the rate of reaction.

MSC: Understanding 31. An exergonic reaction may still be slow if a. the activation energy is high. b. an enzyme is present. c. product concentrations are low. d. reactant concentrations are high.

ANS: A DIF: Moderate REF: 4.4 OBJ: 4.4c Explain how enzymes catalyze reactions and how various factors influence the rate of reaction.

MSC: Analyzing 32. Fill in the blanks with the pair of words below that make the following sentence correct: NADH is ________ compared to NAD+ because NADH has gained ________. a. oxidized; electrons c. reduced; electrons b. oxidized; neutrons d. reduced; neutrons ANS: C DIF: Moderate REF: 4.4 OBJ: 4.4b Describe the oxidation-reduction changes that occur during reactions.

MSC: Understanding 33. Which statement accurately describes membrane phospholipids? a. They are entirely hydrophobic. b. They are entirely hydrophilic. c. They have hydrophilic phosphate head groups and hydrophobic fatty acid tails. d. They have hydrophobic phosphate head groups and hydrophilic fatty acid tails.

ANS: C DIF: Easy REF: 4.5 OBJ: 4.5a Describe the structure of cellular membranes.

MSC: Understanding

34. In a cell membrane, phosphate head groups a. only face the extracellular environment. b. only face the aqueous cytoplasm. c. bind each other via ionic bonds in the interior of the membrane. d. face both the extracellular environment and the cytoplasm.

ANS: D DIF: Easy REF: 4.5 OBJ: 4.5a Describe the structure of cellular membranes.

MSC: Remembering

35. Which of the following molecules would require a transmembrane protein in order to cross a cell membrane? a. O2 c. CO2 b. H2O d. Na+ ANS: D DIF: Moderate REF: 4.5 OBJ: 4.5b Explain the concept of selective permeability of a membrane.

MSC: Applying 36. Weak acids can a. never cross cell membranes. b. cross cell membranes in their uncharged form. c. cross cell membranes in their charged form. d. only cross cell membranes with the aid of a transmembrane protein.

ANS: B

DIF: Easy

REF: 4.5

OBJ: 4.5b Explain the concept of selective permeability of a membrane.

MSC: Understanding 37. You place water containing a radioactive isotope of hydrogen on the outside of a cell. Which of the following will increase the rate at which radioactive water appears on the inside of the cell? a. a decrease in temperature b. an increase in unsaturated fatty acids c. an increase in the fatty acid tail length d. a decrease in membrane surface area ANS: B DIF: Difficult REF: 4.5 OBJ: 4.5c Explain how membranes compartmentalize cells and control the movement of a cell’s molecules.

MSC: Evaluating 38. There is no net movement of water into or out of cells when the cells are in which type of environment? a. isotonic c. hyperosmotic b. hypertonic d. hypotonic ANS: A DIF: Easy REF: 4.5 OBJ: 4.5d Describe the effect of osmosis on cells. MSC:

Remembering

39. The bacterial cell wall offers protection against what type of environment? a. isotonic c. hypotonic b. hypertonic d. endergonic ANS: C DIF: Moderate REF: 4.5 OBJ: 4.5d Describe the effect of osmosis on cells. MSC:

Understanding

40. Endosomes and phagosomes are both types of a. catalysts. c. pseudopods. b. oxidizing agents. d. vesicles.

ANS: D DIF: Easy REF: 4.6 OBJ: 4.6a Describe how endocytosis and phagocytosis transport material into a eukaryotic cell.

MSC: Analyzing 41. Small extracellular particles are taken up via membrane invaginations by________ while ________ takes up larger particles. a. endocytosis; phagocytosis b. phagocytosis; endocytosis c. a pseudopod; endocytosis d. a pseudopod; a lysosome ANS: A DIF: Easy REF: 4.6 OBJ: 4.6a Describe how endocytosis and phagocytosis transport material into a eukaryotic cell.

MSC: Remembering 42. The image below shows the effects of cholera toxin on intestinal cells. Which numbered arrow indicates the step of the toxin entering a cell via endocytosis?

a. 1 b. 2

c. 3 d. 4

ANS: B DIF: Easy REF: 4.6 OBJ: 4.6b Explain how pathogens take advantage of endocytosis and phagocytosis.

MSC: Understanding 43. Bacteria within a phagosome may be destroyed by the fusing of the phagosome with which acidic eukaryotic organelle? a. endoplasmic reticulum c. lysosome b. pseudopod d. vesicle ANS: C DIF: Moderate REF: 4.6 OBJ: 4.6b Explain how pathogens take advantage of endocytosis and phagocytosis.

MSC: Remembering 44. A researcher fluorescently labels the phospholipid head groups of a small number of phospholipids in the outer leaflet of the cell membrane to observe them over time with a microscope. At time zero, all the fluorescent label is concentrated in one spot. At a later time point, the researcher will observe that the fluorescently tagged phospholipids will a. still be together, concentrated in a spot. b. be spread out but will still all be part of the outer leaflet. c. be spread out in the outer leaflet and some will have flip-flopped into the inner leaflet as well. d. It is impossible to predict what will happen to the labeled phospholipids over time.

ANS: B DIF: Difficult REF: 4.5 OBJ: 4.5a Describe the structure of cellular membranes.

45. CASE HISTORY

MSC: Applying

In October 2013, Kelsey was a 28-year-old computer programmer who worked for a prominent technology firm in Silicon Valley. In the middle of the night, Kelsey awoke with abdominal cramps and diarrhea. Her temperature spiked as high as 40C (104F). She had a bad headache and could not retain sufficient fluids. After three days, her fever subsided, but the diarrhea continued (about 20 times a day) and began showing blood. Kelsey was admitted to the hospital, where she was given intravenous fluids to control her dehydration. The physician asked her about her dietary history preceding the onset of symptoms. Kelsey recalled that the night before onset, she had eaten rotisserie chicken cooked at the supermarket. An antibody test confirmed the diagnosis of Salmonella enterica serovar heidelberg. Because of the severity of her symptoms, Kelsey was treated with antibiotics, although sometimes antibiotics may prolong the persistence of Salmonella. When amoxicillin failed to control the infection because of bacterial resistance, ciprofloxacin was used. Ultimately, Kelsey’s illness was one of more than 400 cases in 23 states traced to contaminated chicken from one California farm. Kelsey recovered, but three months later, S. heidelberg could still be detected in her feces.

Kelsey’s diarrhea could have been caused by the Salmonella infection creating a(n) ________ environment in the lumen of her gut, leading water to leave her epithelial cells. a. isotonic c. acidic b. hypertonic d. oxidizing ANS: B DIF: Easy REF: Case History 4.1 OBJ: 4.5d Describe the effect of osmosis on cells. MSC: Understanding COMPLETION 1. Below are shown four different representations of methane. Letter C shows a ________ model.

A

B

C

D

ANS: space-filling DIF: Moderate REF: 4.1 OBJ: 4.1a Describe how atoms form the molecules of life.

MSC: Remembering

2. Below are shown four different representations of methane. Letter B shows a ________ formula.

A

B

C

D

ANS: structural DIF: Moderate REF: 4.1 OBJ: 4.1a Describe how atoms form the molecules of life.

MSC: Remembering

3. Shown below is the outer electron shell of nitrogen. Nitrogen will form ________ bonds with other atoms.

ANS: 3 DIF: Moderate REF: 4.1 OBJ: 4.1a Describe how atoms form the molecules of life.

MSC: Understanding

4. The sharing of electrons between two atoms forms ________ bonds.

ANS: covalent DIF: Moderate REF: 4.1 OBJ: 4.1b Describe the types of bonds atoms can form to make a molecule.

MSC: Remembering 5. The general name for a six-carbon sugar is ________.

ANS: hexose DIF: Moderate REF: 4.2 OBJ: 4.2c Describe the structure of sugars and polysaccharides.

MSC: Remembering 6. Redox reactions involve the movement of ________ from one molecule or atom to another.

ANS: electrons DIF: Easy REF: 4.4 OBJ: 4.4b Describe the oxidation-reduction changes that occur during reactions.

MSC: Remembering SHORT ANSWER 1. Describe the difference between ionic and hydrogen bonds.

ANS: Ionic bonds are electrostatic attractions between atoms having full positive and negative charges (i.e., cations and anions). Hydrogen bonds are weaker and occur between atoms having partial positive and negative charges.

DIF: Difficult REF: 4.1 OBJ: 4.1b Describe the types of bonds atoms can form to make a molecule.

MSC: Analyzing 2. What is a condensation reaction?

ANS: A condensation reaction occurs when water is released as a product when two monomers join together via a covalent bond. Examples include fatty acids condensing with glycerol to form triglycerides and the joining of two amino acids during peptide bond formation.

DIF: Moderate REF: 4.2 OBJ: 4.2a Describe organic molecules, and explain the role of functional groups and the formation of macromolecules.

MSC: Understanding 3. What are some structural differences between cellular DNA and RNA? ANS: DNA is double stranded and contains the sugar deoxyribose and the base thymine. RNA is single stranded and contains the sugar ribose and the base uracil instead of thymine.

DIF: Moderate REF: 4.3 OBJ: 4.3b Describe the structure and diverse functions of RNA. MSC: Analyzing 4. What does amphipathic mean?

ANS: Amphipathic refers to a molecule that has both hydrophilic and hydrophobic regions. Phospholipids are an example of amphipathic molecules.

DIF: Moderate REF: 4.5 MSC: Understanding

OBJ: 4.5a Describe the structure of cellular membranes.

5. What is osmosis and why is it important for cells to maintain osmotic balance?

ANS: Osmosis is the diffusion of water from areas of high water concentration to areas of low water concentration. It is important for cells to maintain water balance because an influx of water can cause cells to swell (and potentially burst) while a net efflux of water can shrink cells and cause abnormally high cell-solute concentrations.

DIF: Difficult REF: 4.5 MSC: Understanding

OBJ: 4.5d Describe the effect of osmosis on cells.

6. The molecular formula of the amino acid glycine is C2H5NO2. What is the molecular formula of a glycine pentapeptide?

ANS: C10H17N5O6 DIF: Difficult REF: 4.3 OBJ: 4.3c Describe the fundamental structure of proteins.

7. CASE HISTORY

MSC: Applying

Water is the most abundant molecule of life—but too much water can be deadly. In the summer of 2010, heavy rains flooded Pakistan, submerging one-fifth of the country. Millions of people were displaced and exposed to water contaminated by microbial pathogens. Diarrheal disease threatened many, especially children.

A ten-year-old boy named Akal developed profuse diarrhea. He showed extreme thirst, but clean drinking water was unavailable. His diarrhea became watery and cloudy with white flecks of intestinal mucus (known as rice-water stool). Akal became listless, his eyes sunken and his skin wrinkled from dehydration.

A nurse observed a sample of Akal’s diarrheal fluid under darkfield microscopy. Numerous bacteria swam rapidly, appearing like “twinkling stars.” The bacteria, comma-shaped bacilli, stained Gram negative.

Later testing confirmed Vibrio cholerae, the cause of cholera. These bacteria produce cholera toxin, a protein complex that causes intestinal epithelial cells to secrete large amounts of chloride ion (Cl−). The high chloride concentration draws out the positively charged sodium ions (Na+). The increased extracellular salt (Na+ and Cl−, or NaCl) causes water to diffuse out of the epithelial cells, leading to dehydration and diarrhea. Without treatment, Akal’s chance of death was 50%.

Akal was treated with oral rehydration therapy (ORT), a method invented by Bangladeshi physicians. ORT involves gradual feeding of a solution containing glucose and NaCl to replace ions and water lost through the diarrhea. Within hours, Akal’s flesh had rehydrated, and within a week he made a full recovery.

Explain the properties of cell membranes that lead to the loss of water from epithelial cells in response to cholera toxin.

ANS: Students should discuss selective permeability of the membrane and its relationship to water and the ions mentioned in the case history.

DIF: Moderate REF: Case History Chapter 4 Intro OBJ: 4.5b Explain the concept of selective permeability of a membrane.

MSC: Applying 8. CASE HISTORY In October 2013, Kelsey was a 28-year-old computer programmer who worked for a prominent technology firm in Silicon Valley. In the middle of the night, Kelsey awoke with abdominal cramps and diarrhea. Her temperature spiked as high as 40°C (104°F). She had a bad headache and could not retain sufficient fluids. After three days, her fever subsided, but the diarrhea continued (about 20 times a day) and began showing blood. Kelsey was admitted to the hospital, where she was given intravenous fluids to control her dehydration. The physician asked her about her dietary history preceding the onset of symptoms. Kelsey recalled that the night before onset, she had eaten rotisserie chicken cooked at the supermarket. An antibody test confirmed the diagnosis of Salmonella enterica serovar heidelberg. Because of the severity of her symptoms, Kelsey was treated with antibiotics, although sometimes antibiotics may prolong the persistence of Salmonella. When amoxicillin failed to control the infection because of bacterial resistance, ciprofloxacin was used. Ultimately, Kelsey’s illness was one of more than 400 cases in 23 states traced to contaminated chicken from one California farm. Kelsey recovered, but three months later, S. heidelberg could still be detected in her feces.

Kelsey’s illness is caused by a facultative intracellular bacterium, meaning when causing infection it may enter human cells. Explain the process by which large particles such as a bacterial cell can enter membrane-covered cells such as human intestinal epithelia.

ANS:

Students should discuss endocytosis. Advanced students may note that this is induced by the bacterium in the case of Salmonella.

DIF: Moderate REF: Case History 4.1 OBJ: 4.6a Describe how endocytosis and phagocytosis transport material into a eukaryotic cell.

MSC: Understanding

Chapter 05: Cell Biology of Bacteria and Eukaryotes LEARNING OBJECTIVES 5.1a Describe the structure and function of the bacterial cell wall, and explain its importance as a target for antibiotics.

5.1b Explain the Gram-negative envelope structure and the role of LPS in pathogenesis.

5.1c Describe the biochemical composition of a bacterial cell.

5.2a Describe the functions of a cell membrane.

5.2b Explain how nutrients are transported and how energy is spent to drive transport.

5.3a Describe the cell wall structure, and explain how it protects bacteria from osmotic shock.

5.3b Explain the function of the Gram-positive cell wall and teichoic acids.

5.3c Explain the function of the Gram-negative outer membrane, LPS, and periplasm.

5.4a Describe how DNA is organized within the bacterial cell.

5.4b Explain how DNA replication is coordinated with cell growth and division.

5.5a Describe how pili and stalks enable bacteria to adhere to a substrate where conditions are favorable.

5.5b Explain how flagellar motility and chemotaxis enable bacteria to respond to environmental change.

5.5c Describe the functions of thylakoids, storage granules, and magnetosomes.

5.6a Explain the structure and interconnection of membranous organelles in the endomembrane system.

5.6b Describe the functions of the Golgi complex, endoplasmic reticulum, and nuclear membrane.

5.6c Explain how the evolutionary process of endosymbiosis led to mitochondria and chloroplasts.

MULTIPLE CHOICE 1. In the scanning electron micrograph of Borrelia burgdorferi shown below, which of the following structures is visible?

a. the outer sheath b. cytoplasmic filaments

c. the genome d. flagellar motors

ANS: A DIF: Easy REF: 5.1 OBJ: 5.1a Describe the structure and function of the bacterial cell wall, and explain its importance as a target for antibiotics.

MSC: Analyzing 2. The cell wall is part of the

a. cell membrane. b. cytoplasm.

c. cell envelope. d. proteome.

ANS: C DIF: Moderate REF: 5.1 OBJ: 5.1a Describe the structure and function of the bacterial cell wall, and explain its importance as a target for antibiotics.

MSC: Understanding 3. Lipopolysaccharides are found in a. Gram-positive bacteria. b. Gram-negative bacteria.

c. archaea. d. eukaryotic microbes.

ANS: B DIF: Easy REF: 5.1 OBJ: 5.1b Explain the Gram-negative envelope structure and the role of LPS in pathogenesis.

MSC: Remembering 4. In Gram-negative bacteria, peptidoglycan is found in the a. cytoplasm. c. outer membrane. b. inner membrane. d. periplasm.

ANS: D DIF: Moderate REF: 5.1 OBJ: 5.1b Explain the Gram-negative envelope structure and the role of LPS in pathogenesis.

MSC: Understanding 5. In the model of a Gram-negative bacterial cell envelope shown below, which line is drawn to the periplasm?

a. 1 b. 2

c. 3 d. 4

ANS: C DIF: Easy REF: 5.1 OBJ: 5.1b Explain the Gram-negative envelope structure and the role of LPS in pathogenesis.

MSC: Applying 6. In the model of a Gram-negative bacterial cell envelope shown below, which line is drawn to lipopolysaccharides?

a. 1 b. 2

c. 3 d. 4

ANS: A DIF: Easy REF: 5.1 OBJ: 5.1b Explain the Gram-negative envelope structure and the role of LPS in pathogenesis.

MSC: Applying 7. The majority of the bacterial cell cytoplasm (by total weight) is a. DNA. c. protein. b. RNA. d. water.

ANS: D DIF: Easy REF: 5.1 OBJ: 5.1c Describe the biochemical composition of a bacterial cell.

MSC: Remembering 8. In an E. coli cell, which molecule is found in only 1–2 copies per cell? a. DNA c. protein b. RNA d. phospholipids ANS: A DIF: Moderate REF: 5.1 OBJ: 5.1c Describe the biochemical composition of a bacterial cell.

MSC: Remembering 9. Which of the following is true about the biochemical composition of a bacterial cell? a. Polyamines give DNA its negative charge. b. Cell cytoplasm content can vary with environmental conditions. c. Proteins are always identical, even with environmental changes. d. Inorganic molecules, such as lipids and sugars, provide nutrients to the cell.

ANS: B DIF: Difficult REF: 5.1 OBJ: 5.1c Describe the biochemical composition of a bacterial cell.

MSC: Understanding 10. The cell membrane stores energy by maintaining a separation of a. DNA. c. ions. b. proteins. d. lipids.

ANS: C DIF: Moderate REF: 5.2 OBJ: 5.2a Describe the functions of a cell membrane.

11. In Gram-negative bacteria the cell membrane separates the

MSC: Understanding

a. b. c. d.

periplasm from the external environment. cytoplasm from the external environment. cytoplasm from the nucleoid.

DNA from the RNA.

ANS: B DIF: Moderate REF: 5.2 OBJ: 5.2a Describe the functions of a cell membrane.

MSC: Understanding

12. In the image below, the circles and squares indicate molecules. The circles are at a higher concentration outside the cell and the squares are at a higher concentration inside the cell. Energy will be released if the circles move __________ the cell or if the squares move __________ the cell.

a. into; out of b. into; into

c. out of; out of d. out of; into

ANS: A DIF: Difficult REF: 5.2 OBJ: 5.2b Explain how nutrients are transported and how energy is spent to drive transport.

MSC: Evaluating 13. In the image below, the circles and squares indicate molecules. The energy released by the transport of the circles out of the cell is used to drive the import of the squares into the cell. This is an example of

a. passive transport.

c. symport coupled transport.

b. facilitated diffusion.

d. antiport coupled transport.

ANS: D DIF: Moderate REF: 5.2 OBJ: 5.2b Explain how nutrients are transported and how energy is spent to drive transport.

MSC: Understanding 14. In the image below, the circles and squares indicate molecules. A transmembrane protein moves circles out of the cell, providing energy to move squares into the cell. Which of the following is correct?

a. Both the circles and the squares move down their concentration gradients. b. Both the circles and the squares move against their concentration gradients. c. The circles move down their concentration gradient and the squares move against their concentration gradient. d. The circles move against their concentration gradient and the squares move down their concentration gradient.

ANS: C DIF: Moderate REF: 5.2 OBJ: 5.2b Explain how nutrients are transported and how energy is spent to drive transport.

MSC: Understanding 15. What structure in bacteria is the target of penicillin (the first antibiotic discovered)? a. the DNA genome c. ribosomes b. the cell wall d. ABC transporters ANS: B DIF: Easy REF: 5.1 OBJ: 5.1a Describe the structure and function of the bacterial cell wall, and explain its importance as a target for antibiotics.

MSC: Remembering 16. The cell wall protects bacterial cells from osmotic shock by a. forming a rigid cage that withstands turgor pressure. b. being impermeable to water, preventing turgor pressure. c. being impermeable to ions and other solutes, preventing osmotic imbalance. d. ensuring cells are only found in environments where turgor pressure will not occur.

ANS: A DIF: Moderate REF: 5.3 OBJ: 5.3a Describe the cell wall structure, and explain how it protects bacteria from osmotic shock.

MSC: Understanding 17. The bacterial cell wall is an attractive target for antibiotics because a. bacterial cells cannot develop resistance to antibiotics that target the cell wall. b. animal cells lack a cell wall. c. the cell wall is unimportant for bacterial survival. d. the cell wall is the only structure bacteria require for survival.

ANS: B DIF: Moderate REF: 5.1 OBJ: 5.1a Describe the structure and function of the bacterial cell wall, and explain its importance as a target for antibiotics.

MSC: Applying 18. Mycoplasma lost their cell walls via reductive evolution. This was possible because a. their cell membranes became extra-thick to compensate. b. it allowed them to not be sensitive to antibiotics that target the cell wall. c. as obligate parasites, they live in environments with constant osmolarity. d. they live in soils with plenty of available moisture.

ANS: C DIF: Difficult REF: 5.3 OBJ: 5.3a Describe the cell wall structure, and explain how it protects bacteria from osmotic shock.

MSC: Analyzing 19. The image below models a

a. b. c. d.

Gram-positive cell envelope.

Gram-negative cell envelope. eukaryotic cell membrane. mycobacterial envelope.

ANS: A DIF: Easy REF: 5.3 OBJ: 5.3b Explain the function of the Gram-positive cell wall and teichoic acids.

MSC: Remembering 20. Which of the following is FALSE of teichoic acids?

a. b. c. d.

They reinforce the cell wall.

They may help pathogens attach to host cells.

They are recognized by the host immune system.

They repel the Gram stain.

ANS: D DIF: Moderate REF: 5.3 OBJ: 5.3b Explain the function of the Gram-positive cell wall and teichoic acids.

MSC: Analyzing 21. The transmission electron micrograph below shows a

a. b. c. d.

Gram-positive cell envelope.

Gram-negative cell envelope. eukaryotic cell membrane. mycobacterial envelope.

ANS: B DIF: Moderate REF: 5.3 OBJ: 5.3c Explain the function of the Gram-negative outer membrane, LPS, and periplasm.

MSC: Applying 22. Murein lipoprotein is a part of the ________ leaflet of the ________ membrane. a. outer; outer c. outer; inner b. inner; outer d. inner; inner ANS: B DIF: Moderate REF: 5.3 OBJ: 5.3c Explain the function of the Gram-negative outer membrane, LPS, and periplasm.

MSC: Remembering 23. A function of lipopolysaccharide is to a. help cells resist phagocytosis. b. aid in outer membrane cell wall attachment. c. allow for mobility to promote chemotaxis. d. provide energy to the cell.

ANS: A DIF: Moderate REF: 5.3 OBJ: 5.3c Explain the function of the Gram-negative outer membrane, LPS, and periplasm.

MSC: Understanding 24. Which of the following helps compact bacterial DNA? a. the origin of replication site c. porins b. supercoils d. pilins ANS: B DIF: Easy REF: 5.4 OBJ: 5.4a Describe how DNA is organized within the bacterial cell.

MSC: Remembering 25. Which of the following is true of growing bacteria?

a. b. c. d.

DNA synthesis occurs continuously.

DNA synthesis occurs during a defined period.

They suspend flagella rotation to put energy toward DNA replication.

DNA synthesis cannot occur at the same time as transcription.

ANS: A DIF: Easy REF: 5.4 OBJ: 5.4b Explain how DNA replication is coordinated with cell growth and division.

MSC: Remembering 26. In the image below, the arrows indicate the partition that separates a bacterial cell into two new daughter cells. This partition is called the

a. stalk. b. S-layer.

c. septum. d. termination site.

ANS: C DIF: Easy REF: 5.4 OBJ: 5.4b Explain how DNA replication is coordinated with cell growth and division.

MSC: Remembering 27. Bacterial cells that expand their cell walls during septation (not before) and septate in parallel planes will form a. chains of rods (bacilli). c. chains of spheres (cocci). b. tetrads of rods (bacilli). d. tetrads of spheres (cocci).

ANS: C DIF: Difficult REF: 5.4 OBJ: 5.4b Explain how DNA replication is coordinated with cell growth and division.

MSC: Evaluating 28. The electron micrograph below shows staphylococci, spherical cells that cluster together like grape bunches. This form transpires when cell wall expansion occurs __________ septation and septation occurs in __________.

a. prior to; parallel planes b. prior to; random orientations

c. during; parallel planes d. during; random orientations

ANS: D DIF: Moderate REF: 5.4 OBJ: 5.4b Explain how DNA replication is coordinated with cell growth and division.

MSC: Applying 29. Which of the following structures is obligatory for all bacterial cells? a. nucleoid c. pili b. flagella d. magnetosomes ANS: A DIF: Easy REF: 5.5 OBJ: 5.5a Describe how pili and stalks enable bacteria to adhere to a substrate where conditions are favorable.

MSC: Understanding 30. Pili and stalks enable bacterial a. adherence. b. chemotaxis.

c. photosynthesis. d. symport.

ANS: A DIF: Easy REF: 5.5 OBJ: 5.5a Describe how pili and stalks enable bacteria to adhere to a substrate where conditions are favorable.

MSC: Remembering 31. While most wild E. coli usually have flagella, many lab strains have lost their flagella. A likely cause of this loss is reductive evolution due to a(n) a. increased need for chemotaxis. b. unchanging environment. c. increased need for magnetotaxis. d. decreased need for magnetotaxis.

ANS: B DIF: Difficult REF: 5.5 OBJ: 5.5b Explain how flagellar motility and chemotaxis enable bacteria to respond to environmental change.

MSC: Analyzing 32. Flagella are required for bacterial a. chemotaxis. b. growth.

c. adherence. d. buoyancy.

ANS: A DIF: Moderate REF: 5.5 OBJ: 5.5b Explain how flagellar motility and chemotaxis enable bacteria to respond to environmental

change.

MSC:

Understanding

33. The transmission electron micrograph of a marine microbe below shows internal structures such as thylakoids. This microbe has what capability that is not present in all bacterial species?

a. adherence b. chemotaxis

c. DNA replication d. photosynthesis

ANS: D DIF: Moderate REF: 5.5 OBJ: 5.5c Describe the functions of thylakoids, storage granules, and magnetosomes.

MSC: Applying 34. Magnetotactic bacteria swim along a magnetic field. To do this these bacteria have __________, which are not present in all bacterial species. a. storage granules c. flagella b. sulfur granules d. gas vesicles ANS: C DIF: Difficult REF: 5.5 OBJ: 5.5c Describe the functions of thylakoids, storage granules, and magnetosomes.

MSC: Applying 35. Which organelle is NOT part of the endomembrane system? a. mitochondrion c. peroxisome b. lysosome d. Golgi complex ANS: A DIF: Easy REF: 5.6 OBJ: 5.6a Explain the structure and interconnection of membranous organelles in the endomembrane system.

MSC: Remembering 36. Ribosomes associate with which endomembrane organelle? a. Golgi complex c. lysosomes b. endoplasmic reticulum d. peroxisomes ANS: B DIF: Easy REF: 5.6 OBJ: 5.6a Explain the structure and interconnection of membranous organelles in the endomembrane system.

MSC: Remembering 37. Which of the following shows the correct path a secreted protein takes in a eukaryotic cell? a. Golgi complex, rough ER, vesicle, cell membrane b. vesicle, rough ER, Golgi complex, cell membrane c. rough ER, Golgi complex, vesicle, cell membrane

d. rough ER, Golgi complex, cell membrane, vesicle ANS: C DIF: Moderate REF: 5.6 OBJ: 5.6b Describe the functions of the Golgi complex, endoplasmic reticulum, and nuclear membrane.

MSC: Understanding 38. Which organelle houses a eukaryotic cell’s genome? a. rough endoplasmic reticulum c. ribosome b. contractile vacuole d. nucleus ANS: D DIF: Easy REF: 5.6 OBJ: 5.6b Describe the functions of the Golgi complex, endoplasmic reticulum, and nuclear membrane.

MSC: Remembering 39. Which organelle arose via endosymbiosis? a. chloroplast b. Golgi apparatus

c. lysosome d. nucleus

ANS: A DIF: Easy REF: 5.6 OBJ: 5.6c Explain how the evolutionary process of endosymbiosis led to mitochondria and chloroplasts.

MSC: Remembering 40. ATP synthase is found in bacterial cell membranes. In eukaryotic cells, ATP synthase is found in the a. cell membrane. c. mitochondrial inner membrane. b. cytoplasm. d. mitochondrial matrix.

ANS: C DIF: Moderate REF: 5.6 OBJ: 5.6c Explain how the evolutionary process of endosymbiosis led to mitochondria and chloroplasts.

MSC: Applying 41. CASE HISTORY In the Indian state of Bihar, a school nurse noticed that a 13-year-old boy, Naranjan, had swelling on his nose and lips. When questioned, Naranjan complained of a pruritic (itchy) rash on his arms and legs. Upon examination, the nurse found pale patches of skin on his back. The pale patches lacked sensation, and there was partial loss of sensation in Naranjan’s wrists and forearms. The patient was diagnosed with leprosy, caused by the bacterium Mycobacterium leprae. The bacteria stain acid-fast and are spread primarily by nasal secretions. For unknown reasons, only 5% of people exposed to the bacteria are susceptible to infection. In a susceptible host, the bacteria can grow slowly for many years without symptoms. They infect the peripheral nerves, causing loss of sensation, and the body’s immune reaction generates skin lesions. To halt the disease, Naranjan was started on a two-year course of multidrug therapy combining dapsone, clofazimine, and rifampin. To monitor hepatotoxicity, liver function tests were ordered. Naranjan’s family and neighbors were screened; one member, an uncle, showed skin lesions. The uncle was treated also. Leprosy is difficult to eradicate because of the long incubation period and because people hide their symptoms, fearing stigma as “lepers.”

Mycobacterium leprae, or leprosy disease, often takes years to develop. Naranjan must use a long-term multidrug therapy to cure it. Why is it necessary to take the drugs for such a long period, and why must he take so many drugs at once? a. Mycobacteria are Gram-negative organisms. They must be killed slowly to prevent release of toxic LPS. b. Mycolic acid within the cell wall reduces nutrient uptake, resulting in slow growth, and excludes some antibiotics. c. Mycobacteria are all highly resistant to antibiotics. d. Mycobacteria don’t have cell walls, so they must be treated with antibiotics that target other structures.

ANS: B DIF: Difficult REF: Case History 5.1 OBJ: 5.1a Describe the structure and function of the bacterial cell wall, and explain its importance as a target for antibiotics. | 5.1c Describe the biochemical composition of a bacterial cell.

MSC: Applying COMPLETION 1. Cells that contain a nucleus are categorized as ________ cells.

ANS: eukaryotic DIF: Easy REF: 5.1 OBJ: 5.1a Describe the structure and function of the bacterial cell wall, and explain its importance as a target for antibiotics.

MSC: Remembering 2. The region within the inner and outer membranes of Gram-negative bacteria is known as the ________.

ANS: periplasm DIF: Moderate REF: 5.1 OBJ: 5.1b Explain the Gram-negative envelope structure and the role of LPS in pathogenesis.

MSC: Remembering 3. The bacterial nucleoid contains loops of DNA that emanate from a central point called the ________.

ANS: origin of replication DIF: Moderate REF: 5.4 OBJ: 5.4a Describe how DNA is organized within the bacterial cell.

MSC: Remembering 4. The fundamental solvent of life is ________.

ANS: water DIF: Moderate

REF: 5.1

OBJ: 5.1c

MSC: Remembering

5. Nutrients may cross a membrane by binding a transporter protein called ________.

ANS: permease DIF: Moderate

REF: 5.2

OBJ: 5.2b

MSC: Remembering

6. Gram- ________ cells have multiple layers of peptidoglycan while Gram- ________ cells have a single layer.

ANS: positive; negative DIF: Moderate

REF: 5.3

OBJ: 5.3

7. Pili and fimbriae are used for ________ to host cells.

MSC: Remembering

ANS: attachment DIF: Moderate

REF: 5.5

OBJ: 5.5

MSC: Remembering

8. The ability of bacterial cells to swim toward favorable environments and away from harmful environments is known as ________.

ANS: chemotaxis DIF: Moderate REF: 5.5 OBJ: 5.5b Explain how flagellar motility and chemotaxis enable bacteria to respond to environmental change.

MSC: Remembering 9. If Na+ is at a higher concentration outside a cell than inside, ________ is the most likely means for sodium ions to enter the cell (and for nothing else to enter or leave).

ANS: facilitated diffusion DIF: Difficult REF: 5.2 OBJ: 5.2b Explain how nutrients are transported and how energy is spent to drive transport.

MSC: Applying 10. In the process of ________, a vesicle fuses with the cell membrane, releasing vesicle contents into the extracellular environment.

ANS: exocytosis DIF: Easy REF: 5.6 OBJ: 5.6a Explain the structure and interconnection of membranous organelles in the endomembrane system.

MSC: Remembering SHORT ANSWER 1. Describe the two types of energy cells used to move molecules across membranes against their concentration gradients.

ANS: Active transport can be powered by two different energy sources. Some transporters are directly powered by ATP hydrolysis. Other transporters use coupled transport—the movement of one molecule down its concentration gradient to provide the energy to move a second molecule against its concentration gradient.

DIF: Moderate REF: 5.2 OBJ: 5.2b Explain how nutrients are transported and how energy is spent to drive transport.

MSC: Understanding 2. Compare and contrast the Gram-negative and Gram-positive cell envelopes.

ANS:

Both Gram-negative and Gram-positive bacteria contain a cell membrane (called the inner membrane in Gram-negative bacteria) and a peptidoglycan cell wall. Gram-negative bacteria have a thin cell wall and an additional outer membrane. Gram-positive bacteria lack an outer membrane but have a thick cell wall.

DIF: Difficult REF: 5.3 OBJ: 5.3a Describe the cell wall structure, and explain how it protects bacteria from osmotic shock.

MSC: Analyzing 3. What evidence would suggest that a newly discovered eukaryotic organelle was formed via endosymbiosis?

ANS: The evidence for mitochondria and chloroplasts being derived via endosymbiosis is the presence of a double membrane (the inner one from the engulfed cell, the outer one from the host eukaryote), the presence of ribosomes, and the presence of DNA. Look for these same traits in the new organelle, as all cells contain a cell membrane, genome, and ribosomes.

DIF: Difficult REF: 5.6 OBJ: 5.6c Explain how the evolutionary process of endosymbiosis led to mitochondria and chloroplasts.

MSC: Applying 4. Explain how bacterial cells can divide so rapidly, some in as little as ten minutes between generations.

ANS: First, prokaryotic genomes are compact, with relatively little noncoding DNA. Second, the DNA replicates continuously, not just during a defined period, as in eukaryotic cells.

DIF: Difficult REF: 5.4 OBJ: 5.4b Explain how DNA replication is coordinated with cell growth and division.

MSC: Applying 5. Would pili be more advantageous to bacteria in a rapidly changing or in an unchanging environment?

Please explain your answer.

ANS: Pili promote bacterial adherence to a substrate. This is an advantage in an unchanging environment that is rich in nutrients. In a rapidly changing environment, being stuck in one place becomes a disadvantage.

DIF: Easy REF: 5.5 OBJ: 5.5a Describe how pili and stalks enable bacteria to adhere to a substrate where conditions are favorable.

MSC: Applying 6. CASE HISTORY Sharon, the CEO of a start-up company, lives in Westchester County, a wooded community north of New York City. She spends her summer weekends e-mailing her managers from the outdoor deck of her home, shaded by tall oak trees. The acorns attract mice and deer, and the leaf litter is full of ticks (Ixodes scapularis).

One evening Sharon’s husband noticed a red rash on her back, consisting of a ring shape several centimeters across, surrounding another red spot in the middle. Sharon recalled seeing this “bull’seye” type of rash on the Internet. The rash was described as the hallmark of Lyme disease, or borreliosis, caused in the United States by the tick-borne bacterium Borrelia burgdorferi (in Europe, by the closely related species Borrelia afzelii). The distinctive rash, erythema migrans (“migrating redness”), begins at the site of a tick bite and expands concentrically as the bacteria migrate outward.

Sharon recalled that a neighbor’s child had suffered crippling arthritis caused by an undetected case of Lyme disease. Another neighbor who contracted Lyme disease had suffered from meningitis (inflammation of the brain lining) and neurological abnormalities, including facial paralysis, ultimately losing his job and his million-dollar home.

The next day Sharon went to her doctor and was treated with the antibiotic doxycycline, a tetracycline derivative that targets the bacterial ribosome. Doxycycline is the antibiotic of choice for B. burgdorferi. Sharon was fortunate to make a full recovery before serious symptoms appeared.

The bull’s-eye rash that is a hallmark of Sharon’s infection is associated with movement of the bacteria from the initial site of tick bite and infection. Discuss how these bacteria move and the cell structures associated with movement.

ANS: The flagellum is a helical protein filament whose rotary motor propels the cell in search of a more favorable environment, including more nutrient-right environments via chemotaxis. For spirochete bacteria such as B. burgdorferi (the cause of Lyme disease) or Treponema pallidum (the cause of syphilis), the flagella wrap around the cell body, enclosed by the outer sheath.

DIF: Moderate REF: Case History Chapter 5 Intro OBJ: 5.5b Explain how flagellar motility and chemotaxis enable bacteria to respond to environmental change.

MSC: Applying 7. CASE HISTORY Jennifer, age 23, had just graduated from college with a Fulbright fellowship to study sociology in Africa. Before leaving the United States, she obtained a routine physical exam at a large city hospital.

Upon returning home from the hospital, she developed a swelling in her leg. When she returned to the hospital, she was told that the swelling represented an allergic reaction and was given antiinflammatory agents. The swelling grew, and within a day the skin ruptured with a bloody discharge.

Upon return to the emergency room, Jennifer at last received the correct diagnosis of methicillinresistant staphylococcus infection (MRSA). A nurse commented that hospital visitors can acquire MRSA; the infectious agent is endemic at many hospitals in the United States and is very difficult to eradicate. She showed Jennifer a micrograph of the bacteria, Staphylococcus aureus, which septate in alternating division planes, thus forming clusters of cells. Jennifer required many weeks of treatment with the antibiotics doxycycline and clindamycin (inhibits protein synthesis) before the infection resolved, and she had to postpone her fellowship for a year.

Methicillin, the antibiotic to which MRSA is characteristically resistant, targets the cell wall. Discuss the structure of the cell wall in a bacterial cell like those of MRSA and how antibiotics can target this structure without harming the patient.

ANS: Outside the cell membrane, Gram-positive bacteria have a thick cell wall with multiple layers of peptidoglycan, threaded by teichoic acids. Peptidoglycan is synonymous with murein (“wall molecule”) and consists of parallel polymers of disaccharides called glycan chains. Peptidoglycan, or murein, is unique to bacteria, never found in human cells. For this reason, antibiotics that target peptidoglycan synthesis may have minimal side effects for a patient.

DIF: Moderate

REF: Case History 5.2

OBJ: 5.1a Describe the structure and function of the bacterial cell wall, and explain its importance as a target for antibiotics.

MSC: Applying

Chapter 06: Bacterial Growth, Nutrition, and Differentiation LEARNING OBJECTIVES 6.1a Compare heterotrophy, autotrophy, phototrophy, and chemotrophy.

6.1b Describe the importance of the nitrogen and carbon cycles and the role of microbes in their maintenance.

6.1c Discuss biofilms and their relevance to infectious diseases.

6.2a Explain how pure cultures are obtained and why they are important in medicine.

6.2b Distinguish synthetic, complex, selective, and differential media and their use in clinical microbiology.

6.2c Describe the various ways bacterial growth is measured, and explain the advantages and disadvantages of each method.

6.3a Discuss the phases of a typical bacterial growth curve.

6.3b Explain how bacterial growth correlates to disease.

6.3c Describe the purpose of continuous culture and how it correlates to the human digestive tract.

6.4a Describe how environmental changes can alter the shape of a growth curve.

6.4b List different classes of microbes based on their preferred environmental niches (pH, temperature, salt).

6.4c Identify the biological properties that allow different classes of microbes to grow in extreme environments.

6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

6.5b Explain how both aerobes and anaerobes can cause disease.

6.5c Discuss the basic differences between respiration and fermentation and how this impacts where an organism grows.

6.6a Discuss how biofilms develop.

6.6b Explain the importance of biofilms to infection.

6.6c Describe the process of sporulation, and explain how spores impact certain infections.

MULTIPLE CHOICE 1. Despite the incredibly fast division of bacterial cells, we are not surrounded by large mountains of these cells. This can be explained by the fact that bacteria a. produce too much toxic iron. b. require a host cell to grow. c. are outcompeted by viruses. d. run out of nitrogen.

ANS: D DIF: Easy REF: 6.1 OBJ: 6.1a Compare heterotrophy, autotrophy, phototrophy, and chemotrophy.

MSC: Understanding 2. Which of the following is needed as an important enzyme cofactor for microbial growth? a. Na+ c. sulfur 2+ b. Mg d. oxygen ANS: B DIF: Moderate REF: 6.1 OBJ: 6.1a Compare heterotrophy, autotrophy, phototrophy, and chemotrophy.

MSC: Understanding

3. Examine the media recipes shown below. What ingredients make Luria Bertani a complex medium as opposed to a chemically defined minimal medium?

a. b. c. d.

tryptone and NaCl tryptone and yeast extract NaCl and yeast extract Luria Bertani is a chemically defined minimal medium.

ANS: B DIF: Moderate REF: 6.1 OBJ: 6.2b Distinguish synthetic, complex, selective, and differential media and their use in clinical microbiology.

MSC: Understanding 4. Which of the following could describe the relationship between the cyanobacterium Nostoc and E. coli in terms of the carbon cycle? a. Nostoc is a heterotroph and produces carbohydrates; E. coli breaks down the carbohydrates to generate CO2. b. Nostoc is an autotroph and produces carbohydrates; E. coli breaks down the carbohydrates to generate CO2. c. Nostoc produces CO2 that E. coli turns into carbohydrates. d. E. coli produces carbohydrates that Nostoc uses as energy to produce more carbohydrates.

ANS: B DIF: Moderate REF: 6.1 OBJ: 6.1b Describe the importance of the nitrogen and carbon cycles and the role of microbes in their maintenance.

MSC: Applying 5. Which of the following statements regarding examples of chemotrophy is FALSE? a. Glucose is an oxidized compound that freely donates electrons to NAD, a more reduced compound. b. Glucose is a reduced compound that freely donates electrons to NAD, a more oxidized compound. c. NAD plays an important role in chemotrophic metabolism. d. Glucose is an important chemotrophic carbon source.

ANS: A DIF: Moderate REF: 6.1 OBJ: 6.1b Describe the importance of the nitrogen and carbon cycles and the role of microbes in their maintenance.

MSC: Applying 6. What is the correct term for the chemical conversion shown below?

N2 → NH4+

a. phototrophy b. nitrification

c. denitrification d. nitrogen fixation

ANS: D DIF: Moderate REF: 6.1 OBJ: 6.1b Describe the importance of the nitrogen and carbon cycles and the role of microbes in their maintenance.

MSC: Applying 7. The advantage of the plating method shown on the left over the plating method shown on the right is that the plating method on the left can be used to

a. b. c. d.

isolate pure colonies. culture viable organisms. produce confluent growth. quantify the number of organisms in a given bacterial sample.

ANS: D DIF: Moderate REF: 6.2 OBJ: 6.2a Explain how pure cultures are obtained and why they are important in medicine.

MSC: Analyzing 8. Fastidious organisms would be best grown on which type of media? a. enriched c. minimal b. synthetic d. selective ANS: A DIF: Easy REF: 6.2 OBJ: 6.2b Distinguish synthetic, complex, selective, and differential media and their use in clinical microbiology.

MSC: Understanding 9. Mannitol salts agar is a medium that contains a high concentration of salt (7.5%) and mannitol as a fermentable carbon source. Few organisms are able to grow on it because of its high salt concentration. Organisms that can grow and ferment mannitol will produce an acid that interacts with the pH indicator in the media, turning it yellow. Nonmannitol-fermenting organisms grow without any change to the media. Which of the following correctly describes this medium? a. selective c. selective and differential b. differential d. neither selective nor differential ANS: C DIF: Difficult REF: 6.2 OBJ: 6.2b Distinguish synthetic, complex, selective, and differential media and their use in clinical microbiology.

MSC: Analyzing 10. Which of the following is true about MacConkey medium? a. The dye crystal violet makes the plate differential. b. The plate is both selective and differential. c. The bile salts make this plate selective for Gram-positive organisms. d. Nonlactose fermenters will appear as red colonies.

ANS: B DIF: Moderate REF: 6.2 OBJ: 6.2b Distinguish synthetic, complex, selective, and differential media and their use in clinical microbiology.

MSC: Understanding 11. Which of the following can be used to directly count bacterial cells without the use of a microscope? a. viable counts b. optical density c. a fluorescence-activated cell sorter d. a Petroff-Hauser counting chamber ANS: C DIF: Difficult REF: 6.2 OBJ: 6.2c Describe the various ways bacterial growth is measured and explain the advantages and disadvantages of each method.

MSC: Remembering 12. Which of the following is NOT a problem with the viable count method of cell quantification? a. It underestimates the number of living cells in the culture. b. It takes too long if the goal is to immediately study cells at a particular growth phase. c. It is not accurate for organisms whose cells remain attached (for example, Streptococci growing in chains). d. It is not useful for living cells.

ANS: D DIF: Easy REF: 6.2 OBJ: 6.2c Describe the various ways bacterial growth is measured and explain the advantages and disadvantages of each method.

MSC: Understanding 13. Which of the following can be most efficiently used to measure bacterial growth in real time? a. FACS b. spectrophotometer c. a Petroff-Hauser counting chamber d. a fluorescent microscope ANS: B DIF: Moderate REF: 6.2 OBJ: 6.2c Describe the various ways bacterial growth is measured, and explain the advantages and disadvantages of each method.

MSC: Understanding 14. Which of the following is NOT required for microorganisms to grow and divide? a. DNA replication b. binary fission c. equatorial septum formation d. conjugation ANS: D DIF: Easy REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Understanding 15. A culture of Salmonella increases from 20 cells to over 10,000 cells in just three hours. This statement best represents a. lag phase. c. budding. b. doubling time. d. exponential growth.

ANS: D DIF: Moderate REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Understanding

16. If a researcher starts with 14 organisms at time 0, how many organisms will they have after 9 generations, assuming exponential growth? a. 126 c. 7,168 b. 512 d. 14,336 ANS: C DIF: Moderate REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Applying 17. Which of the following is NOT happening during the lag phase of growth? a. Cells are at their largest. b. Genes for growth in the specific environment are turned on. c. Cell components are being synthesized. d. Cells are detecting their environment.

ANS: A DIF: Easy REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Remembering 18. In the figure below, in which phase does the number of bacterial cells dividing equal the number of cells dying?

a. 1 b. 2

c. 3 d. 4

ANS: C DIF: Easy REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Remembering 19. In the figure below, in which phase(s) do(es) the number of bacteria change exponentially?

a. 1 and 2 b. 2 only

c. 2 and 4 d. 4 only

ANS: C DIF: Moderate REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Remembering 20. Bacteria begin to participate in quorum sensing at the ________ phase of growth. a. late log c. stationary b. log d. death ANS: A DIF: Easy REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Remembering 21. A new enzyme that helps protect a bacterial cell from reactive oxygen species has been discovered. It can be expected that the gene that codes for this enzyme will be expressed in the ________ phase of growth. a. lag c. late log b. log d. stationary ANS: D DIF: Moderate REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Applying 22. When a microorganism is found in an environment below its minimum growth temperature, a. the cell dies. b. growth stops because the cell membrane melts. c. growth slows or stops because enzymatic processes become sluggish. d. growth slows but does not stop.

ANS: C DIF: Easy REF: 6.4 OBJ: 6.4a Describe how environmental changes can alter the shape of a growth curve.

MSC: Understanding 23. What classification is also given to barophilic organisms that grow at the ocean floor? a. mesophilic c. halophilic b. psychrophilic d. acidophilic ANS: B DIF: Easy REF: 6.4 OBJ: 6.4b List different classes of microbes based on their preferred environmental niches (pH, temperature, salt).

MSC: Remembering

24. An environment with a high osmolarity has a a. low salt concentration. b. high pH.

c. high water activity. d. low water activity.

ANS: D DIF: Moderate REF: 6.4 OBJ: 6.4b List different classes of microbes based on their preferred environmental niches (pH, temperature, salt).

MSC: Applying 25. A ________ bacteria is most likely to be a human pathogen. a. mesophilic c. hyperthermophilic b. thermophilic d. psychrophilic ANS: A DIF: Moderate REF: 6.4 OBJ: 6.4b List different classes of microbes based on their preferred environmental niches (pH, temperature, salt).

MSC: Remembering 26. Which of the following cellular components could be found in high concentrations in a halophilic microorganism? a. Na+/ K+ ion pump c. cold-tolerant enzymes b. citric acid d. asuperoxide dismutase ANS: A DIF: Moderate REF: 6.4 OBJ: 6.4c Identify the biological properties that allow different classes of microbes to grow in extreme environments.

MSC: Applying 27. Production of urease by Helicobacter pylori allows it to a. sense when it has entered the intracellular environment of its host. b. survive in basic conditions. c. increase production of ion pumps. d. neutralize stomach pH to survive in acidic conditions.

ANS: D DIF: Moderate REF: 6.4 OBJ: 6.4c Identify the biological properties that allow different classes of microbes to grow in extreme environments.

MSC: Understanding 28. Which of the following is NOT a toxic by-product of oxygen metabolism? a. superoxide c. hydrogen peroxide b. hydroxide radicals d. dihydrogen oxide ANS: D DIF: Easy REF: 6.5 OBJ: 6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

MSC: Understanding 29. Consider the tube shown below. What type of organism would grow only at the bottom of the tube?

a. microaerophile b. aerotolerant anaerobe

c. strict anaerobe d. strict aerobe

ANS: C DIF: Moderate REF: 6.5 OBJ: 6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

MSC: Applying 30. Consider the tube shown below. What type of organism would grow in the middle of the tube?

a. microaerophile b. aerotolerant anaerobe

c. strict anaerobe d. strict aerobe

ANS: A DIF: Moderate REF: 6.5 OBJ: 6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

MSC: Applying 31. Consider the tube shown below. What type of organism would grow throughout the tube regardless of the presence of oxygen?

a. microaerophile b. aerotolerant anaerobe

c. strict anaerobe d. strict aerobe

ANS: B DIF: Moderate REF: 6.5 OBJ: 6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

MSC: Applying 32. Consider the tube shown below. What type of organism is killed by the presence of oxygen?

a. microaerophile b. aerotolerant anaerobe

c. strict anaerobe d. strict aerobe

ANS: C DIF: Moderate REF: 6.5 OBJ: 6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

MSC: Understanding 33. Strict anaerobes die in the presence of oxygen because they a. are vulnerable to reactive oxygen species. b. are not able to get enough energy without using oxygen as a terminal electron acceptor. c. do not use oxygen as a terminal electron acceptor.

d. Strict anaerobes do not die in the presence of oxygen.

ANS: A DIF: Moderate REF: 6.5 OBJ: 6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

MSC: Understanding 34. A facultative organism might prefer aerobic respiration over fermentation when carbohydrates become scarce because it gets a. less energy from aerobic respiration. b. more energy from fermentation. c. more energy from aerobic respiration. d. Facultative organisms never prefer aerobic respiration to fermentation.

ANS: C DIF: Difficult REF: 6.5 OBJ: 6.5c Discuss the basic differences between respiration and fermentation and how this impacts where an organism grows.

MSC: Applying 35. The purpose of the palladium packet in the anaerobic jar is to a. catalyze a reaction between H2 and residual O2 in the jar to remove all the O2. b. remove CO2 that can be converted to O2. c. provide O2 for aerobic respiration. d. provide N2 for protein synthesis.

ANS: A DIF: Moderate REF: 6.5 OBJ: 6.5c Discuss the basic differences between respiration and fermentation and how this impacts where an organism grows.

MSC: Understanding 36. Which of the following is NOT an example of a bacterial organism that can form a biofilm? a. Bacillus anthracis b. Pseudomonas aeruginosa c. Escherichia coli d. All bacterial organisms can form biofilms.

ANS: A DIF: Moderate REF: 6.6 OBJ: 6.6a Discuss how biofilms develop.

MSC: Understanding

37. Bacterial organisms form a biofilm to a. claim territory and fight off competing organisms of a different species. b. attach to a surface in an area where food is plentiful. c. find a food source when nutrients are scarce. d. mate with other bacterial organisms of the same or different species.

ANS: B DIF: Easy REF: 6.6 OBJ: 6.6a Discuss how biofilms develop.

MSC: Remembering

38. Which of the following is NOT used for attachment in biofilm formation? a. lipopolysaccharides b. glycoproteins c. pili d. Lipopolysaccharides, glycoproteins, and pili are all used for attachment in biofilm formation.

ANS: A DIF: Moderate REF: 6.6 OBJ: 6.6a Discuss how biofilms develop.

MSC: Remembering

39. Which of the following is NOT necessary for endospore formation?

a. exopolysaccharide formation b. peptidoglycan synthesis

c. dipicolinic acid synthesis d. calcium transport

ANS: A DIF: Moderate REF: 6.6 OBJ: 6.6c Describe the process of sporulation and explain how spores impact certain infections.

MSC: Applying 40. If an error occurred during the sporulation process and small, acid-soluble proteins were NOT included in the spore, the effect would be that the spore would a. only exist for 100 years. c. be less resistant to heat. b. be more likely to germinate. d. be less resistant to ultraviolet light.

ANS: D DIF: Difficult REF: 6.6 OBJ: 6.6c Describe the process of sporulation and explain how spores impact certain infections.

MSC: Applying 41. CASE HISTORY A young mother who recently emigrated from Uganda brought her sick 18-month-old infant, Mirembe, to a New York City emergency room. The infant was crying uncontrollably, especially when the physician tried to move her head. Meningitis (an infection of the spinal fluid and membrane surrounding the brain) was suspected, and a spinal tap was performed to collect cerebrospinal fluid (CSF). The fluid, which appeared cloudy, was sent to the laboratory.

CSF should be free of microbes, but a microscopic examination revealed Gram-negative bacilli.

The technician cultured the sample on various solid media. The organism failed to grow on blood agar plates containing intact red blood cells (RBCs) but did grow on a medium containing lysed RBCs (called chocolate agar because of its color). The organism recovered from the CSF also grew on a relatively simple medium containing growth factors known as X and V. The diagnosis was meningitis caused by the bacterium Haemophilus influenzae. The child received antibiotics and made a full recovery.

The blood agar plates used to culture Mirembe’s sample contain intact red blood cells and agar.

Organisms that are capable of lysing the red blood cells may produce green-appearing zones of partial hemolysis or clear-appearing zones of complete hemolysis around colonies that are easily visually distinguishable. This medium is best described as a. selective. c. chemically defined. b. differential. d. synthetic.

ANS: B DIF: Moderate REF: 6.Intro | Case History Chapter 6 Intro OBJ: 6.2b Distinguish synthetic, complex, selective, and differential media and their use in clinical microbiology.

MSC: Applying COMPLETION 1. A ________ contains only the most basic compounds an organism needs to grow and nothing more.

ANS: chemically defined minimal medium; minimal defined media DIF: Easy REF: 6.1 OBJ: 6.1a Compare heterotrophy, autotrophy, phototrophy, and chemotrophy.

MSC: Remembering 2. If a researcher is trying to isolate a pure culture of Staphylococcus aureus from the skin lesion of an infected individual, they would use appropriate sampling techniques and would specifically have to culture the microorganism onto a(n) ________ plate.

ANS: agar DIF: Moderate REF: 6.2 OBJ: 6.2a Explain how pure cultures are obtained and why they are important in medicine.

MSC: Understanding 3. Direct counting of bacterial cells under the microscope can be accomplished using a(n) ________.

ANS: hemocytometer DIF: Easy REF: 6.2 OBJ: 6.2c Describe the various ways bacterial growth is measured and explain the advantages and disadvantages of each method.

MSC: Remembering 4. Most bacteria in nature grow at a very slow rate, a situation that can be mimicked using a ________.

ANS: chemostat DIF: Moderate REF: 6.3 OBJ: 6.3c Describe the purpose of continuous culture and how it correlates to the human digestive tract.

MSC: Understanding 5. Mesophilic proteins are ________ flexible than psychrophilic proteins.

ANS: less DIF: Moderate REF: 6.4 OBJ: 6.4b List different classes of microbes based on their preferred environmental niches (pH, temperature, salt).

MSC: Understanding 6. Aerobic bacteria are capable of using ________ as a terminal electron acceptor in the electron transport chain.

ANS: oxygen DIF: Easy REF: 6.5 OBJ: 6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

MSC: Remembering 7. Within aquatic environments, bacteria are mainly found associated with surfaces in the form of a ________.

ANS: biofilm DIF: Easy MSC: Analyzing

REF: 6.6

OBJ: 6.6a Discuss how biofilms develop.

8. The production of ________ mechanisms in a biofilm helps maintain the viability of a biofilm during an infection.

ANS: antibiotic resistance DIF: Moderate

REF: 6.6

OBJ: 6.6b Explain the importance of biofilms to infection.

MSC: Applying

SHORT ANSWER 1. What effect would the loss of heterotrophs have on the carbon cycle and the world?

ANS: Heterotrophs are important for converting organic carbon sources to CO2, which is then used by autotrophs to regenerate organic carbon sources. Loss of heterotrophs would lead to a buildup in organic carbon sources and a depletion of CO2, which would eventually inhibit the function of autotrophs.

DIF: Difficult REF: 6.1 OBJ: 6.1b Describe the importance of the nitrogen and carbon cycles and the role of microbes in their maintenance.

MSC: Evaluating 2. Explain metabolically why bacteria grow faster in complex media than in minimal media.

ANS: Growth in complex media conserves energy for an organism, as many important cellular components they could synthesize on their own are already present in the media. This allows the cells to use that energy toward growth and not “waste” it on synthesizing cell components.

DIF: Moderate REF: 6.2 OBJ: 6.2b Distinguish synthetic, complex, selective, and differential media and their use in clinical microbiology.

MSC: Understanding 3. What is a batch culture? Describe how it can be used to illustrate the bacterial growth curve.

ANS: A batch culture is growth in a flask or test tube where no fresh media is added during incubation.

Because nutrient levels will decline and waste cultures will build up, all phases of the growth curve will be reached in the batch culture.

DIF: Moderate REF: 6.3 OBJ: 6.3a Discuss the phases of a typical bacterial growth curve.

MSC: Applying 4. List the three factors that complicate measuring bacterial growth in a human host. Describe how each one makes measuring bacterial growth difficult.

ANS: The three factors are microbial competition, collaboration with resident microbiota, and the host’s immune system. A variety of answers are possible for how each one inhibits the measurement of bacterial growth.

DIF: Difficult REF: 6.3 OBJ: 6.3b Explain how bacterial growth correlates to disease.

5. Why are extremophiles not a pathogenic threat to humans?

ANS:

MSC: Analyzing

Extremophiles grow in an environment with some sort of extreme condition. The human body does not offer an environment extreme enough for an extremophile to survive.

DIF: Moderate REF: 6.4 OBJ: 6.4a Describe how environmental changes can alter the shape of a growth curve.

MSC: Analyzing 6. How are many microorganisms able to grow at pH levels outside the functional pH range of their enzymes?

ANS: Bacterial membranes are relatively impermeable to protons, preventing them from entering the cell and making it possible for organisms to grow at a pH outside of the range in which their enzymes will function.

DIF: Difficult REF: 6.4 OBJ: 6.4c Identify the biological properties that allow different classes of microbes to grow in extreme environments.

MSC: Analyzing 7. How is it possible for strict anaerobic bacteria to cause a disease in humans?

ANS: There are many parts of the human body where oxygen is absent that make for perfect environments for the growth of strict anaerobic organisms.

DIF: Difficult REF: 6.5 OBJ: 6.5b Explain how both aerobes and anaerobes can cause disease.

MSC: Analyzing 8. List and describe two differences between anaerobic respiration and fermentation.

ANS: Anaerobic respiration requires the use of an electron transport chain, while fermentation does not.

Fermentation produces ATP through substrate level phosphorylation only, while anaerobic respiration uses oxidative phosphorylation.

DIF: Moderate REF: 6.5 OBJ: 6.5c Discuss the basic differences between respiration and fermentation and how this impacts where an organism grows.

MSC: Analyzing 9. Examine the figure on endospore formation shown. What is happening at stage III and how does it lead to the remarkable heat and chemical resistance of endospores?

ANS: The mother cell is engulfing the forespore at stage III. This adds a second plasma membrane layer to the endospore, resulting in a space for the formation of the cortex. These extra layers all give increased protection to the endospore and help it to be resistant to heat and chemicals.

DIF: Difficult REF: 6.6 OBJ: 6.6c Describe the process of sporulation and explain how spores impact certain infections.

MSC: Analyzing 10. CASE HISTORY Robert, a 21-year-old software salesman from Dallas, Texas, presented to the Parkland Hospital emergency room with three days of cramping pain in the midgastric and lower abdominal areas. He had no nausea, vomiting, or diarrhea. Upon examination, the patient screamed in severe pain when the clinician pressed on his lower right abdomen. Blood samples were obtained and sent for bacteriological culture. A blood culture bottle incubated in air appeared sterile, whereas another blood culture bottle placed in a special chamber that removed oxygen grew thick with bacteria. A subsequent exploratory laparoscopy, in which a small incision is used to perform surgery and minimize scarring, revealed a grossly inflamed appendix that released a liter of pus when removed.

The diagnosis was appendicitis caused by the anaerobic bacterium Bacteroides fragilis—a common intestinal microbe.

How should the microbe causing Robert’s infection be cultured? Will all of the microbes present in a sample taken from the site of his infection be able to grow in this culture? Explain your answer.

ANS:

Several techniques for culturing anaerobes are used today. One popular way to culture anaerobes, especially on agar plates, employs an anaerobe jar. Agar plates streaked with the organism are placed into a sealed jar with a foil packet that releases H2 and CO2 gases. A palladium packet hanging from the jar lid catalyzes a reaction between the H2 and O2 in the jar to form H2O, which effectively removes O2 from the chamber. The CO2 released is required by the anaerobe to produce key metabolic intermediates.

Aerobic organisms and those that require other specialized conditions such as increased CO2, though they may have been present in the sample, will not grow in this culture.

DIF: Moderate REF: Case History 6.3 OBJ: 6.5a Differentiate anaerobes from aerobes and describe how they are cultured.

MSC: Applying 11. CASE HISTORY A fecal sample from a patient with diarrhea was streaked onto MacConkey lactose agar medium, a medium that selectively prevents the growth of Gram-positive bacteria but will differentiate Gramnegative bacteria that can ferment lactose from those that cannot. The next day, several different types of bacterial colonies were visible on the agar plate. Some were red; others were white. The white colonies led the clinical microbiologist to suspect that the patient was infected with the Gram-negative bacillus Salmonella enterica serovar typhimurium.

MacConkey lactose agar medium selectively prevents the growth of Gram-positive bacteria but will differentiate Gram-negative bacteria that can ferment lactose from those that cannot. The use of these types of media, called selective and differential media, are extremely helpful when microbiologists already have an idea of the pathogen present. What led the microbiologist to believe that the white colonies were Salmonella enterica serovar typhimurium?

ANS: Salmonella produced white colonies. MacConkey indicates lactose-positive cells by turning red. Since Salmonella is not a lactose fermenter, the colonies did not turn red.

DIF: Moderate REF: Case History 6.1 OBJ: 6.2b Distinguish synthetic, complex, selective, and differential media and their use in clinical microbiology.

MSC: Applying

Chapter 07: Bacterial Metabolism LEARNING OBJECTIVES 7.1a Define the major classes of energy-yielding metabolism, including photosynthesis, organotrophy, and lithotrophy.

7.1b Explain the importance of energy and entropy for living cells.

7.1c State the role of enzymes in controlling metabolic biochemistry.

7.2a Describe how catabolism converts many complex food molecules to a few kinds of catabolites.

7.2b Explain how catabolism yields energy and how the energy is stored for use.

7.2c Describe how the energy carriers ATP and NADH transfer energy between energy-yielding and energyspending reactions.

7.3a Describe how sugar is catabolized to pyruvate via glycolysis, and explain how these catabolic reactions generate ATP and NADH. 7.3b Explain how pyruvate is further catabolized by fermentation or by the TCA cycle (when oxygen is available).

7.3c Explain how bacterial catabolic reactions are used in clinical tests to identify a pathogen.

7.4a Describe how NADH transfers electrons to electron transport proteins of the ETS and ultimately to the terminal electron acceptor, such as O2.

7.4b Explain how the transfer of electrons from one oxidoreductase to the next, yielding energy, is coupled to the pumping of H+ across the membrane.

7.4c Explain how lithotrophy yields energy by oxidizing mineral electron donors instead of organic molecules.State an example of how environmental lithotrophy affects human health.

7.5a Describe how photosynthesis harvests light to generate ATP and NADPH, while releasing O2.

7.5b Describe how a photosynthetic microbe fixes CO2 into biomass.

7.5c Explain the importance of photosynthesis for human health.

7.6a Describe how intermediates of metabolism are reduced and assembled into biomolecules.

7.6b Explain how bacteria and archaea fix nitrogen gas into ammonium ion and incorporate nitrogen into biomolecules.

MULTIPLE CHOICE 1. Which numbered arrow(s) in the figure below point(s) to a step that indicates reactions carried out by autotrophs?

a. 1 b. 2

c. 3 d. 1 and 2

ANS: A DIF: Moderate REF: 7.1 OBJ: 7.1a Define the major classes of energy-yielding metabolism, including photosynthesis, organotrophy, and lithotrophy.

MSC: Understanding 2. Which numbered arrow(s) in the figure below point(s) to a step that indicates reactions carried out by heterotrophs?

a. 1 b. 2

c. 3 d. 1 and 2

ANS: B DIF: Moderate REF: 7.1 OBJ: 7.1a Define the major classes of energy-yielding metabolism, including photosynthesis, organotrophy, and lithotrophy.

MSC: Understanding 3. An organism gains energy using H2 as an electron donor and sulfate as an electron acceptor. This organism is categorized as an a. aerobic lithotroph. c. aerobic organotroph. b. anaerobic lithotroph. d. anaerobic organotroph.

ANS: B DIF: Moderate REF: 7.1 OBJ: 7.1a Define the major classes of energy-yielding metabolism, including photosynthesis, organotrophy, and lithotrophy.

MSC: Analyzing 4. Which of the following is true of energy and living cells? a. Organisms can create their own energy. b. Organisms do not require inputs of energy from the environment. c. Organisms require inputs of energy from the environment to survive. d. Only heterotrophic organisms require environmental energy inputs to survive.

ANS: C DIF: Easy REF: 7.1 OBJ: 7.1b Explain the importance of energy and entropy for living cells.

MSC: Understanding 5. A metabolic reaction can only provide energy to cells if a. G is negative. c. S is negative. b. G is positive. d. S is positive.

ANS: A

DIF: Easy

REF: 7.1

OBJ: 7.1b Explain the importance of energy and entropy for living cells.

MSC: Understanding 6. Enzymes increase reaction rates by a. increasing activation energies. b. decreasing activation energies. c. increasing the concentration of reactants. d. increasing the concentration of products.

ANS: B DIF: Easy REF: 7.1 OBJ: 7.1c State the role of enzymes in controlling metabolic biochemistry.

MSC: Understanding 7. Which of the following is true of metabolic reactions? a. They are all catalyzed by enzymes. b. They all release energy. c. Organisms use the same reactions to maintain life. d. They always use or produce ATP. ANS: A DIF: Moderate REF: 7.1 OBJ: 7.1c State the role of enzymes in controlling metabolic biochemistry.

MSC: Analyzing 8. What catabolite is produced first from the catabolism of starch or cellulose? a. acetyl-CoA c. glucose b. amino acids d. glycerol ANS: C DIF: Moderate REF: 7.2 OBJ: 7.2a Describe how catabolism converts many complex food molecules to a few kinds of catabolites.

MSC: Understanding 9. The hydrolysis of a protein into amino acids is an example of a. anabolism. c. lithotrophy. b. catabolism. d. nitrogen fixation.

ANS: B DIF: Easy REF: 7.2 OBJ: 7.2a Describe how catabolism converts many complex food molecules to a few kinds of catabolites.

MSC: Understanding 10. The human genome does NOT code for enzymes that can catabolize a. cellulose. c. fatty acids. b. starch. d. proteins.

ANS: A DIF: Moderate REF: 7.2 OBJ: 7.2a Describe how catabolism converts many complex food molecules to a few kinds of catabolites.

MSC: Understanding 11. Which reactions both require energy? a. ATP hydrolysis and reduction of NAD+ b. ATP hydrolysis and oxidation of NADH c. ATP production and reduction of NAD+ d. ATP production and oxidation of NADH ANS: C DIF: Moderate REF: 7.2 OBJ: 7.2c Describe how the energy carriers ATP and NADH transfer energy between energyyielding and energy-spending reactions.

MSC: Understanding

12. The reaction shown below

a. b. c. d.

is an anabolic reaction. is a hydrolysis reaction. is a redox reaction. has a negative change in free energy.

ANS: A DIF: Difficult REF: 7.2 OBJ: 7.2b Explain how catabolism yields energy and how the energy is stored for use.

MSC: Analyzing 13. What molecule is depicted below?

a. ADP b. ATP

c. NAD+ d. NADH

ANS: A DIF: Easy REF: 7.2 OBJ: 7.2b Explain how catabolism yields energy and how the energy is stored for use.

MSC: Remembering 14. In a metabolic reaction involving the conversion of NADH to NAD+, NADH ________ electrons and ________ energy. a. loses; gains c. loses; loses b. gains; gains d. gains; loses ANS: C DIF: Moderate REF: 7.2 OBJ: 7.2c Describe how the energy carriers ATP and NADH transfer energy between energyyielding and energy-spending reactions.

MSC: Understanding 15. During glycolysis glucose is ________ and NAD+ is ________. a. oxidized; reduced c. oxidized; oxidized b. reduced; oxidized d. reduced; reduced ANS: A DIF: Moderate REF: 7.3 OBJ: 7.3a Describe how sugar is catabolized to pyruvate via glycolysis, and explain how these catabolic reactions generate ATP and NADH. MSC: Applying 16. Which metabolic pathway is shown below?

a. Calvin cycle b. glycolysis

c. oxidative phosphorylation d. tricarboxylic acid cycle

ANS: B DIF: Easy REF: 7.3 OBJ: 7.3a Describe how sugar is catabolized to pyruvate via glycolysis, and explain how these catabolic reactions generate ATP and NADH. MSC: Remembering 17. Starting with one glucose molecule, the products of glycolysis include a. 1 pyruvate, 2 net ATP, and 2 NADPH. b. 1 pyruvate, 4 net ATP, and 2 NADH. c. 2 pyruvate, 4 net ATP, and 4 NADH. d. 2 pyruvate, 2 net ATP, and 2 NADH. ANS: D DIF: Moderate REF: 7.3 OBJ: 7.3a Describe how sugar is catabolized to pyruvate via glycolysis, and explain how these catabolic reactions generate ATP and NADH. MSC: Understanding 18. Humans harness microbial ________ to preserve foods and retain caloric value. a. glycolysis c. TCA cycle b. fermentation d. aerobic respiration ANS: B DIF: Moderate REF: 7.3 OBJ: 7.3b Explain how pyruvate is further catabolized by fermentation or by the TCA cycle (when oxygen is available).

MSC: Applying 19. If cells cannot carry out fermentation or respiration, which numbered box in the figure below indicates the first step of glycolysis to be affected?

a. 1 b. 2

c. 3 d. 4

ANS: C DIF: Difficult REF: 7.3 OBJ: 7.3b Explain how pyruvate is further catabolized by fermentation or by the TCA cycle (when oxygen is available).

MSC: Evaluating 20. Which numbered box in the figure below most clearly shows a redox reaction?

a. 1 b. 2

c. 3 d. 4

ANS: C DIF: Moderate REF: 7.2 OBJ: 7.2b Explain how catabolism yields energy and how the energy is stored for use.

MSC: Analyzing 21. In the phenol broth red test (shown below), a yellow color and bubble (as shown in the far left vial) indicate

a. acidic fermentation products and gas production. b. acidic fermentation products and no gas production. c. fermentation of peptides to amines and gas production.

d. fermentation of peptides to amines and no gas production.

ANS: A DIF: Difficult REF: 7.3 OBJ: 7.3c Explain how bacterial catabolic reactions are used in clinical tests to identify a pathogen.

MSC: Applying 22. A bacterial electron transport system (ETS) is shown below. If the quinone pool were artificially depleted, the expected consequences would be a buildup of ________ and ________ H2O production.

a. NADH; increased b. NADH; decreased

c. NAD; increased d. NAD; decreased

ANS: B DIF: Difficult REF: 7.4 OBJ: 7.4a Describe how NADH transfers electrons to electron transport proteins of the ETS and ultimately to the terminal electron acceptor, such as O2.

MSC: Evaluating 23. Why does respiration yield more energy per glucose than fermentation? a. Fermentation uses more enzymes, and enzymes are costly to make. b. Fermentation requires oxygen. c. In fermentation, the carbons in glucose do not become fully oxidized. d. Fermentation is only found in prokaryotic organisms; eukaryotes need more energy.

ANS: C DIF: Moderate REF: 7.3 OBJ: 7.3b Explain how pyruvate is further catabolized by fermentation or by the TCA cycle (when oxygen is available).

MSC: Evaluating 24. At the end of the TCA cycle most of the energy originally present in glucose is now found in a. CO2. c. NADPH. b. NADH. d. ATP. ANS: B DIF: Moderate REF: 7.4 OBJ: 7.4a Describe how NADH transfers electrons to electron transport proteins of the ETS and ultimately to the terminal electron acceptor, such as O2.

MSC: Analyzing 25. If in the ETS electrons are passed from a to b and finally accepted by c, then a. a is a stronger electron acceptor than b. b. a is a stronger electron acceptor than c. c. a is a stronger electron donor than b. d. c is a stronger electron donor than b.

ANS: C DIF: Moderate REF: 7.4 OBJ: 7.4b Explain how the transfer of electrons from one oxidoreductase to the next, yielding energy, is coupled to the pumping of H+ across the membrane.

MSC: Applying 26. Oxidative phosphorylation requires a. ATP synthase.

c. NAD+.

b. carbon dioxide.

d. pyruvate dehydrogenase.

ANS: A DIF: Moderate REF: 7.4 OBJ: 7.4b Explain how the transfer of electrons from one oxidoreductase to the next, yielding energy, is coupled to the pumping of H+ across the membrane.

MSC: Analyzing 27. Which of the following is NOT powered by the proton motive force in bacteria? a. ATP synthase c. drug efflux b. DNA replication d. flagella rotation ANS: B DIF: Easy REF: 7.4 OBJ: 7.4b Explain how the transfer of electrons from one oxidoreductase to the next, yielding energy, is coupled to the pumping of H+ across the membrane.

MSC: Remembering 28. Under what environmental conditions might bacteria produce ATP more readily? a. slightly acidic environment b. slightly basic environment c. greatly elevated temperature d. greatly decreased temperature ANS: A DIF: Difficult REF: 7.4 OBJ: 7.4b Explain how the transfer of electrons from one oxidoreductase to the next, yielding energy, is coupled to the pumping of H+ across the membrane.

MSC: Applying 29. A bacterium that lacks a respiratory chain likely relies on what metabolic strategy for energy production? a. aerobic lithotrophy b. anaerobic lithotrophy c. photosynthesis d. glycolysis followed by fermentation ANS: D DIF: Moderate REF: 7.4 OBJ: 7.4b Explain how the transfer of electrons from one oxidoreductase to the next, yielding energy, is coupled to the pumping of H+ across the membrane.

MSC: Analyzing 30. Nitrate contamination of water can poison infants. One source of nitrate is a. lithotrophs that use ammonia as an electron donor. b. anaerobes that use nitrate as a terminal electron acceptor. c. methanogens that oxidize H2. d. oxygenic photosynthesis.

ANS: A DIF: Difficult REF: 7.4 OBJ: 7.4c Explain how lithotrophy yields energy by oxidizing mineral electron donors instead of organic molecules. MSC: Applying 31. Oxygenic photosynthesis strips electrons from a. CO2. c. H2S. b. H2O. d. O2.

ANS: B DIF: Easy REF: 7.5 OBJ: 7.5a Describe how photosynthesis harvests light to generate ATP and NADPH, while releasing O2. MSC: Remembering 32. During photosynthesis, ATP is produced via a. oxidation of glucose. b. transfer of a phosphate from NADPH onto ADP.

c. ATP synthase powered by a pmf. d. ATP synthase powered directly by light.

ANS: C DIF: Easy REF: 7.5 OBJ: 7.5a Describe how photosynthesis harvests light to generate ATP and NADPH, while releasing O2. MSC: Understanding 33. What metabolic strategy is summarized in this equation: C6H12O6 + 6H2O + 6O2 → 12H2O + 6CO2 a. oxygenic photosynthesis c. anaerobic organotrophy b. aerobic lithotrophy d. aerobic organotrophy ANS: D DIF: Easy REF: 7.1 OBJ: 7.1a Define the major classes of energy-yielding metabolism, including photosynthesis, organotrophy, and lithotrophy.

MSC: Remembering 34. The enzyme Rubisco is involved in a. ATP production. b. carbon fixation.

c. fermentation. d. nitrogen fixation.

ANS: B DIF: Easy REF: 7.5 OBJ: 7.5b Describe how a photosynthetic microbe fixes CO2 into biomass.

MSC: Remembering 35. A benefit of the Calvin cycle to humans is that it a. releases oxygen into the atmosphere, which humans require for aerobic respiration. b. creates biomass, which is the basis for food chains. c. synthesizes antibiotics that can help combat emerging pathogens. d. reduces nitrogen, eliminating the need for expensive fertilizers.

ANS: B DIF: Easy REF: 7.5 OBJ: 7.5b Describe how a photosynthetic microbe fixes CO2 into biomass.

MSC: Understanding 36. Photosynthesis helps mitigate global warming by a. adding O2 to the atmosphere. b. removing O2 from the atmosphere. c. removing CO2 from the atmosphere. d. adding CO2 to the atmosphere.

ANS: C DIF: Easy REF: 7.5 OBJ: 7.5c Explain the importance of photosynthesis for human health.

MSC: Understanding 37. Which molecule is used as a reducing agent in biosynthetic reactions? a. ATP c. NADPH b. NADH d. glucose ANS: C DIF: Easy REF: 7.6 OBJ: 7.6a Describe how intermediates of metabolism are reduced and assembled into biomolecules.

MSC: Remembering 38. Plants ________ can still grow without fertilizer. a. with rhizobia symbionts b. that do not need proteins c. that do not need nucleic acids d. that can carry out the Calvin cycle

ANS: A DIF: Easy REF: 7.6 OBJ: 7.6b Explain how bacteria and archaea fix nitrogen gas into ammonium ion and incorporate nitrogen into biomolecules.

MSC: Applying 39. Which of the pathways below are in the correct order for the flow of electrons from glucose to oxygen in aerobic respiration? a. glycolysis, ETS, TCA c. TCA, glycolysis, ETS b. glycolysis, fermentation, TCA d. glycolysis, TCA, ETS ANS: D DIF: Easy REF: 7.3 OBJ: 7.3b Explain how pyruvate is further catabolized by fermentation or by the TCA cycle (when oxygen is available).

MSC: Remembering 40. Which of the following is true of nitrogen fixation? a. It requires ATP but not reducing agents. b. It requires reducing agents but not ATP. c. It is an important reaction carried out by organisms in all three domains of life. d. Only prokaryotes have the metabolic capability to fix nitrogen.

ANS: D DIF: Moderate REF: 7.6 OBJ: 7.6b Explain how bacteria and archaea fix nitrogen gas into ammonium ion and incorporate nitrogen into biomolecules.

MSC: Understanding 41. CASE HISTORY Shane, a 21-year-old college student, was spending spring break at the beach in Cancun, where he frequently ordered drinks from the beachfront stands. Upon his return to classes, Shane fell ill with a fever of 38.9C (102F), severe abdominal cramps, and watery diarrhea.

By the second day, Shane had blood in his stools, a condition known as dysentery. Upon admission to the hospital, Shane showed dehydration, and his rectal exam was very painful with bleeding.

A fecal culture was performed on Hektoen agar, a selective medium for Gram-negative bacteria; bile salts exclude Gram-positives. Hektoen agar also differentiates among the enteric Gram-negative pathogens Salmonella, Shigella, and Escherichia. Most Salmonella species show black colonies due to H2S formation from thiosulfate, whereas Escherichia species form colonies that are orange from lactose fermentation. Shane’s culture produced translucent colonies, indicating Shigella species, which neither ferment lactose nor reduce thiosulfate to H2S. Serotyping (determining which antibodies react with the pathogen) confirmed the species Shigella flexneri, a common cause of “traveler’s diarrhea” from drinking contaminated water. Shane received intravenous rehydration and was given the antibiotic quinolone, chosen based on laboratory tests of the pathogen’s antibiotic sensitivity. Afterward, Shane made a full recovery.

On Hektoen agar, Salmonella colonies appear black, whereas Escherichia species form colonies that are orange. This helps microbiologists identify the organisms, and is actually representative of a. differences in the enzymes produced by different species, which normally allow them to utilize nutrients in their environments. b. differences in the color of the cells themselves. c. how quickly the organisms are able to grow on this medium and how quickly they take up dyes. d. the virulence or pathogenicity of the organisms (whether they can infect humans).

ANS: A DIF: Easy REF: Case History Chapter 7 Intro OBJ: 7.1c State the role of enzymes in controlling metabolic biochemistry.

MSC: Applying 42. CASE HISTORY

Brianna was a 2-month-old, formula-fed infant in a rural community in Nebraska. Brianna’s mother noticed signs of blueness around the baby’s mouth and fingers. One night after feeding, Brianna had trouble breathing, and her face had a peculiar lavender color. The infant became lethargic, salivated excessively, and had diarrhea and vomiting. An EMT came and took blood samples, which appeared brown and failed to turn pink when exposed to air. The EMT diagnosed methemoglobinemia, a condition in which toxic levels of nitrite oxidize hemoglobin and prevent it from receiving oxygen. The nitrite oxidized hemoglobin is called methemoglobin; elevated levels can cause asphyxiation and death. A solution of methylene blue, a reducing agent, was administered by IV to reduce (add electrons to) the hemoglobin in Brianna’s blood.

Nitrite forms in the digestive tract by bacterial reduction of nitrate during anaerobic respiration.

The well water from which Brianna’s formula was prepared was tested and found to contain high levels of nitrate, enough to cause methemoglobinemia. Brianna’s parents were surprised because they had felt no ill effect from the water. But an infant’s stomach pH is high, allowing bacteria to reduce nitrate to nitrite, which may then oxidize hemoglobin.

The nitrite in the baby’s blood was formed by her intestinal bacteria using nitrate (NO3-) as a terminal electron acceptor for anaerobic respiration, with nitrite (NO2-) as the product. Bacteria can multiply more quickly by utilizing oxygen as a terminal electron acceptor in which process? a. fermentation c. aerobic respiration b. the pentose phosphate pathway d. lithotrophy ANS: C DIF: Moderate REF: Case History 7.2 OBJ: 7.4a Describe how NADH transfers electrons to electron transport proteins of the ETS and ultimately to the terminal electron acceptor, such as O2.

MSC: Applying COMPLETION 1. The Embden-Myerhof-Parnas (EMP) pathway is also known as ________.

ANS: glycolysis DIF: Moderate REF: 7.3 OBJ: 7.3a Describe how sugar is catabolized to pyruvate via glycolysis, and explain how these catabolic reactions generate ATP and NADH. MSC: Remembering 2. If Fe3+ is the final electron acceptor at the end of an electron transport system, the waste product is ________.

ANS: Fe2+ DIF: Moderate REF: 7.4 OBJ: 7.4a Describe how NADH transfers electrons to electron transport proteins of the ETS and ultimately to the terminal electron acceptor, such as O2.

MSC: Applying 3. The metabolic pathway used by cyanobacteria and plants to fix carbon dioxide into sugar is known as the ________ cycle.

ANS: Calvin DIF: Moderate REF: 7.5 OBJ: 7.5b Describe how a photosynthetic microbe fixes CO2 into biomass.

MSC: Remembering 4. Biosynthetic reactions are also known as ________ reactions.

ANS: anabolic DIF: Easy REF: 7.6 OBJ: 7.6a Describe how intermediates of metabolism are reduced and assembled into biomolecules.

MSC: Remembering 5. The ultimate goal of the Calvin cycle is to produce ________.

ANS: biomass, glucose, sugar, carbohydrate, monosaccharides, glyceraldehyde-3-phosphate DIF: Easy REF: 7.5 OBJ: 7.5b Describe how a photosynthetic microbe fixes CO2 into biomass.

MSC: Understanding SHORT ANSWER 1. Yeast ferments hexose sugars into two molecules of ethanol and two molecules of CO2. This reaction is used in bread making—the CO2 causes the dough to rise. Explain why this reaction is so sensitive to temperature, slowing down considerably at lower temperatures.

ANS: The negative G of this reaction is driven mostly by an increase in entropy (S is positive). G = H − TS. Since there is a negative sign in front of TS, a positive S leads to a negative G. S is multiplied by temperature (T), so at lower temperatures the reaction is slowed considerably.

DIF: Difficult REF: 7.1 OBJ: 7.1b Explain the importance of energy and entropy for living cells.

MSC: Applying 2. Compare and contrast anaerobic respiration and fermentation. How are they similar and how do they differ?

ANS: They are similar in that neither requires oxygen, but there are several differences. Fermentation is a means to regenerate NAD+ (by putting the electrons from NADH back onto pyruvate) when inorganic electron acceptors are not available. The only ATP produced per glucose are the two net produced during glycolysis. In anaerobic respiration glucose is completely oxidized to CO2. The NADH produced donates electrons to an ETS that does not use oxygen as a final electron acceptor.

DIF: Moderate REF: 7.4 OBJ: 7.4b Explain how the transfer of electrons from one oxidoreductase to the next, yielding energy, is coupled to the pumping of H+ across the membrane.

MSC: Applying 3. Compare and contrast ATP production in chloroplasts and mitochondria. How are they similar and how do they differ?

ANS: In both, ATP is generated by a membrane-embedded ATP synthase that is powered by proton motive force (pmf). They differ in the initial electron donors in the ETS that generates the pmf. In mitochondria NADH is the initial electron donor. In chloroplasts light energy boosts an electron in chlorophyll to a high energy level to pass through the ETS; this electron is replaced by stripping electrons from water, producing O2.

DIF: Moderate REF: 7.5 OBJ: 7.5a Describe how photosynthesis harvests light to generate ATP and NADPH, while releasing O2.

MSC: Applying 4. Why does sugar production from CO2 require NADPH in addition to ATP? In other words, why is ATP not sufficient?

ANS: CO2 is an oxidized form of carbon. Sugars are reduced compared to CO2. While ATP can supply the energy needed to produce one glucose from six CO2 molecules, a reducing agent such as NADPH is required to supply the electrons needed to reduce the CO2.

DIF: Moderate REF: 7.5 OBJ: 7.5b Describe how a photosynthetic microbe fixes CO2 into biomass.

MSC: Applying 5. Lithotrophs donate electrons from inorganic reduced molecules directly to an ETS to generate a proton motive force. Why might these lithotrophs still possess the tricarboxylic acid cycle?

ANS: The TCA cycle is usually considered a catabolic pathway that produces NADH. However, many TCA intermediates form the substrates for biosynthetic pathways. For example, some amino acids can be formed in a single step from TCA intermediate.

DIF: Moderate REF: 7.6 OBJ: 7.6a Describe how intermediates of metabolism are reduced and assembled into biomolecules.

MSC: Analyzing 6. Explain how catabolism yields energy and how that energy is stored for use.

ANS: Catabolism is the breakdown of organic molecules to produce energy in the form of ATP. During catabolism, specific enzymes break down larger molecules into catabolites. These catabolites feed into various pathways to yield ATP. The energy is stored within the chemical bonds of ATP and is released when ATP is converted to ADP. DIF: Moderate REF: 7.2 OBJ: 7.2b Explain how catabolism yields energy and how the energy is stored for use.

MSC: Understanding 7. CASE HISTORY Tonya, age 32, was spending a warm June weekend at a beach in Massachusetts. The water near shore looked clear, although farther offshore the water had a reddish tint. Tonya dug up a pail of clams and cooked them thoroughly. After dinner, her lips grew numb and her fingers tingled. She felt nauseated and had difficulty walking across the room. Her speech became slurred, but she managed to dial 911. The ambulance got her to the hospital in time for Tonya to have her stomach pumped and receive assistance breathing. The physician explained to Tonya that she had contracted paralytic shellfish poisoning from consumption of clams contaminated by an algal toxin. The toxin, called saxitoxin, accumulates in the clams as they feed on the algae; cooking does not affect the toxin. At that time, Massachusetts had a ban on shellfish consumption because of a high population density of saxitoxin-producing algae, Alexandrium tamarense, a cause of “red tide.”

Though Tonya suffered from consumption of saxitoxin, the organisms that produced it are valuable to humans as well. Explain how these myxotrophic organisms produce a product necessary to our respiration.

ANS: The oxygenic photosynthesis of these mixed metabolism microbes (called mixotrophs) contributes greatly to the O2 production and CO2 consumption of marine ecosystems. All the oxygen we breathe comes from photosynthesis—much of it by microbes. Photosynthesis fundamentally supports all the ecosystems of our biosphere.

DIF: Moderate REF: Case History 7.3 OBJ: 7.5c Explain the importance of photosynthesis for human health.

MSC: Applying

Chapter 08: Bacterial Genetics and Biotechnology LEARNING OBJECTIVES 8.1a Describe the structure of a bacterial genome, and explain how it differs from a eukaryotic genome.

8.1b Explain what a plasmid is, and describe the role of plasmids in the spread of antibiotic resistance genes.

8.2a Explain how bidirectional semiconservative DNA replication copies the circular chromosome of a bacterium during cell division.

8.2b Explain the steps of replication by DNA polymerase, including initiation, elongation, and termination.

8.3a Explain the different kinds of mutations and how they occur.

8.3b Describe different ways that a cell repairs DNA damage, preventing or reversing mutations.

8.4a Describe the use of plasmids, restriction enzymes, and gel electrophoresis to analyze DNA. 8.4b Explain the formation of a recombinant DNA molecule, and describe applications in medical technology.

8.4c Explain the use of DNA hybridization and DNA sequencing technology.

8.5a Describe the different kinds and functions of RNA products that are made from DNA. 8.5b Explain how RNA polymerase copies a sequence of DNA to form mRNA. 8.5c For biotechnology, describe the use of reverse transcriptase to make a cDNA copy of an mRNA. 8.6a Explain the relationship between transcription and translation in bacteria.

8.6b Describe the ribosomal steps of initiation, elongation, and termination. Explain how these steps may be targeted by antibacterial agents.

8.6c Explain how proteins may require folding and secretion.

8.7a Describe how and why a cell regulates expression of a virulence gene.

8.7b Outline the levels of gene regulation. Explain why it is useful to regulate gene expression at different levels.

MULTIPLE CHOICE 1. The image shown below is a space-filling model of

a. DNA. b. peptidoglycan.

c. protein. d. lipid.

ANS: A DIF: Easy REF: 8.1 OBJ: 8.1a Describe the structure of a bacterial genome, and explain how it differs from a eukaryotic genome.

MSC: Understanding 2. Which of the following is found in eukaryotic but not prokaryotic genomes? a. promoters c. introns b. operons d. genes ANS: C DIF: Moderate REF: 8.1 OBJ: 8.1a Describe the structure of a bacterial genome, and explain how it differs from a eukaryotic genome.

MSC: Remembering 3. Each bacterial species has a unique a. cell shape. b. cell wall.

c. genome. d. glycolytic pathway.

ANS: C DIF: Easy REF: 8.1 OBJ: 8.1a Describe the structure of a bacterial genome, and explain how it differs from a eukaryotic genome.

MSC: Understanding 4. Which of the following is true of plasmids? a. They can be the entire genome. b. They are common in eukaryotic cells. c. They are usually linear. d. They may contain antibiotic resistance genes.

ANS: D DIF: Easy REF: 8.1 OBJ: 8.1b Explain what a plasmid is, and describe the role of plasmids in the spread of antibiotic resistance genes.

MSC: Remembering 5. Plasmids usually contain genes that are a. important for cell survival in all environments. b. important for cell survival in particular environments. c. not important for cell survival in any environments. d. composed of single-stranded DNA. ANS: B DIF: Moderate REF: 8.1 OBJ: 8.1b Explain what a plasmid is, and describe the role of plasmids in the spread of antibiotic resistance genes.

MSC: Understanding 6. In the image of a nucleoside below, which arrow is pointing to the 2 carbon of deoxyribose?

a. A b. B

c. C d. D

ANS: C DIF: Moderate REF: 8.2 OBJ: 8.2a Explain how bidirectional semiconservative DNA replication copies the circular chromosome of a bacterium during cell division.

MSC: Understanding 7. In the active site of DNA polymerase, which monomer will form correct base pairs with a C in the template strand? a. dATP c. dGTP b. dCTP d. dTTP ANS: C DIF: Easy REF: 8.2 OBJ: 8.2a Explain how bidirectional semiconservative DNA replication copies the circular chromosome of a bacterium during cell division.

MSC: Understanding 8. An E. coli cell whose DNA contains N14 is placed in media with dNTPs containing a heavy isotope of nitrogen, N15, which incorporates into newly synthesized DNA. After one cell division, what will the DNA in the daughter cells look like? a. One cell will have both strands of the helix N14; the other cell will have both strands of the helix N15. b. One cell will have mostly N14 with a little bit of N15; the other cell will have mostly N15 with a little N14. c. Each cell will have one strand of N14 and one strand of N15. d. It is impossible to predict what the DNA in the daughter cells will look like.

ANS: C DIF: Difficult REF: 8.2 OBJ: 8.2a Explain how bidirectional semiconservative DNA replication copies the circular chromosome of a bacterium during cell division.

MSC: Evaluating 9. To radioactively tag newly synthesized DNA, which phosphate in the figure below would need to be radioactive?

a. A b. B

c. C d. A, B, or C would work.

ANS: C DIF: Moderate REF: 8.2 OBJ: 8.2b Explain the steps of replication by DNA polymerase, including initiation, elongation, and termination.

MSC: Understanding 10. DNA replication begins at a chromosomal region called the a. activator. c. origin. b. initiator. d. promoter.

ANS: C DIF: Moderate REF: 8.2 OBJ: 8.2b Explain the steps of replication by DNA polymerase, including initiation, elongation, and termination.

MSC: Remembering 11. Which of the choices in the figure below has the correct 5 and 3 DNA end designations?

a. b. c. d.

1 = 5 1 = 3 1 = 5 1 = 3

2 = 3 2 = 5 2 = 5 2 = 3

3 = 5 3 = 5 3 = 3 3 = 5

4 = 3 4 = 3 4 = 3 4 = 5

ANS: B DIF: Moderate REF: 8.2 OBJ: 8.2a Explain how bidirectional semiconservative DNA replication copies the circular chromosome of a bacterium during cell division.

MSC: Analyzing

12. The activity of what enzyme is modeled in the figure below?

a. gyrase b. helicase

c. DNA polymerase d. primase

ANS: A DIF: Easy REF: 8.2 OBJ: 8.2b Explain the steps of replication by DNA polymerase, including initiation, elongation, and termination.

MSC: Understanding 13. Which of the following lists enzymes involved in DNA replication in the order they act? a. primase, helicase, DNA polymerase b. helicase, DNA polymerase, primase c. primase, DNA polymerase, helicase d. helicase, primase, DNA polymerase ANS: D DIF: Easy REF: 8.2 OBJ: 8.2b Explain the steps of replication by DNA polymerase, including initiation, elongation, and termination.

MSC: Applying 14. TAT is a codon for the amino acid tyrosine (Tyr). If a mutation changes TAT to TAA, what kind of mutation has occurred?

a. frameshift b. missense

c. nonsense d. silent

ANS: C DIF: Easy REF: 8.3 OBJ: 8.3a Explain the different kinds of mutations and how they occur.

MSC: Applying 15. TAT is a codon for the amino acid tyrosine (Tyr). If a mutation changes TAT to CAT, what kind of mutation has occurred?

a. frameshift b. missense

c. nonsense d. silent

ANS: B DIF: Easy REF: 8.3 OBJ: 8.3a Explain the different kinds of mutations and how they occur.

MSC: Applying 16. A mutation known as a pyrimidine dimer is usually caused by a. acridine orange. c. UV light. b. DNA polymerase errors. d. X-rays.

ANS: C DIF: Moderate REF: 8.3 OBJ: 8.3b Describe different ways that a cell repairs DNA damage, preventing or reversing mutations.

MSC: Remembering 17. Which repair process leads to an abasic site as part of the repair pathway? a. base excision repair c. recombination b. methyl mismatch repair d. SOS repair ANS: A DIF: Moderate REF: 8.3 OBJ: 8.3b Describe different ways that a cell repairs DNA damage, preventing or reversing mutations.

MSC: Understanding 18. Which of the following processes can introduce mutations into damaged DNA? a. base excision repair c. recombination b. methyl mismatch repair d. SOS repair ANS: A DIF: Easy REF: 8.3 OBJ: 8.3b Describe different ways that a cell repairs DNA damage, preventing or reversing mutations.

MSC: Remembering

19. During gel electrophoresis the ________ DNA fragments migrate more quickly and move further down the gel toward the ________ pole. a. larger; negative c. smaller; negative b. larger; positive d. smaller; positive ANS: D DIF: Moderate REF: 8.4 OBJ: 8.4a Describe the use of plasmids, restriction enzymes, and gel electrophoresis to analyze DNA. MSC: Understanding 20. RFLP analysis requires which tools? a. restriction enzymes and gel electrophoresis b. restriction enzymes and PCR c. gel electrophoresis and PCR d. gel electrophoresis and DNA sequencing ANS: A DIF: Difficult REF: 8.4 OBJ: 8.4a Describe the use of plasmids, restriction enzymes, and gel electrophoresis to analyze DNA. MSC: Evaluating 21. Recombinant human insulin is safely produced in bacteria. Which of the following is the correct sequence of steps needed to produce such a transgenic bacterium? a. transform bacteria, ligate, hybridize insulin cDNA and plasmid b. hybridize insulin cDNA and plasmid, ligate, transform bacteria c. hybridize insulin cDNA and plasmid, transform bacteria, ligate d. ligate, hybridize insulin cDNA and plasmid, transform bacteria ANS: B DIF: Easy REF: 8.4 OBJ: 8.4b Explain the formation of a recombinant DNA molecule, and describe applications in medical technology.

MSC: Applying 22. Shown below are various DNA probes. What technique is illustrated in this diagram?

a. b. c. d.

DNA hybridization DNA sequencing recombinant DNA production PCR

ANS: A DIF: Easy REF: 8.4 OBJ: 8.4c Explain the use of DNA hybridization and DNA sequencing technology.

MSC: Understanding 23. Which of the following RNAs gets translated into protein? a. mRNA c. tRNA b. rRNA d. sRNA

ANS: A DIF: Easy REF: 8.5 OBJ: 8.5a Describe the different kinds and functions of RNA products that are made from DNA. MSC: Remembering 24. If a portion of the template strand of a gene has the sequence 5 TTGCAGCT 3, what is the sequence of the RNA transcribed from this template? a. 5 AACGTCGA 3 c. 5 AGCUGCAA 3 b. 5 AACGUCGA 3 d. 5 AGCTGCAA 3 ANS: C DIF: Moderate REF: 8.5 OBJ: 8.5b Explain how RNA polymerase copies a sequence of DNA to form mRNA. MSC: Applying 25. During transcription termination a. sigma disengages from RNA polymerase. b. RNA polymerase disengages from the DNA. c. ribosomes disengage from the mRNA. d. DNA replicates the termination sequence.

ANS: B DIF: Easy REF: 8.5 OBJ: 8.5b Explain how RNA polymerase copies a sequence of DNA to form mRNA. MSC: Remembering 26. What enzyme is used to produce cDNA? a. DNA polymerase III b. DNA ligase

c. RNA polymerase d. reverse transcriptase

ANS: D DIF: Moderate REF: 8.5 OBJ: 8.4c Explain the use of DNA hybridization and DNA sequencing technology.

MSC: Remembering 27. Which of the following is NOT normally found in human cells? a. cDNA c. mRNA b. DNA d. tRNA ANS: A DIF: Moderate REF: 8.5 OBJ: 8.4c Explain the use of DNA hybridization and DNA sequencing technology.

MSC: Applying 28. The most likely signature of an operon would be ________ distances between consecutive coding regions and ________. a. large; functional association of the gene products b. large; gene products involved in different pathways c. short; gene products involved in different pathways d. short; functional association of the gene products ANS: C DIF: Difficult REF: 8.5 OBJ: 8.5a Describe the different kinds and functions of RNA products that are made from DNA. MSC: Analyzing 29. Ribosomes are composed of a. protein only. b. RNA only.

ANS: C

DIF: Easy

c. both protein and rRNA. d. both protein and tRNA. REF: 8.6

OBJ: 8.6b Describe the ribosomal steps of initiation, elongation, and termination. Explain how these steps may be targeted by antibacterial agents.

MSC: Remembering 30. What energy source is used to drive translation? a. ATP b. GTP c. NADPH d. the energy released when peptide bonds form ANS: B DIF: Easy REF: 8.6 OBJ: 8.6b Describe the ribosomal steps of initiation, elongation, and termination. Explain how these steps may be targeted by antibacterial agents.

MSC: Remembering 31. An antibiotic that inhibits peptidyl transferase activity likely binds to a. aminoacyl-tRNA synthetase. c. a 30S ribosome subunit. b. mRNA. d. a 50S ribosome subunit.

ANS: D DIF: Moderate REF: 8.6 OBJ: 8.6b Describe the ribosomal steps of initiation, elongation, and termination. Explain how these steps may be targeted by antibacterial agents.

MSC: Applying 32. Except for the initiating fMet tRNA, what is the order of sites that tRNAs take through a ribosome? a. first E, then P, and finally A c. first E, then A, and finally P b. first A, then P, and finally E d. first P, then A, and finally E ANS: B DIF: Easy REF: 8.6 OBJ: 8.6b Describe the ribosomal steps of initiation, elongation, and termination. Explain how these steps may be targeted by antibacterial agents.

MSC: Remembering 33. EF-G is involved in a. transcription initiation. b. transcription elongation.

c. translation initiation. d. translation elongation.

ANS: D DIF: Moderate REF: 8.6 OBJ: 8.6b Describe the ribosomal steps of initiation, elongation, and termination. Explain how these steps may be targeted by antibacterial agents.

MSC: Understanding 34. After translation a. all proteins are folded and secreted. b. some proteins are folded but all are secreted. c. all proteins are folded and some are also secreted. d. some proteins are folded and another subset are secreted.

ANS: C DIF: Easy REF: 8.6 OBJ: 8.6c Explain how proteins may require folding and secretion.

MSC: Applying 35. Phase variation controls protein levels by a. altering the DNA sequence. b. changing the rate of mRNA translation. c. changing the rate of mRNA stability. d. changing the rate of protein stability.

ANS: A DIF: Moderate REF: 8.7 OBJ: 8.7b Outline the levels of gene regulation. Explain why it is useful to regulate gene expression at different levels.

MSC: Understanding

36. Bacteria regulate virulence gene expression because a. the genes need to be expressed all the time. b. the genes do not need to be expressed all the time, and regulation saves energy. c. the genes do not need to be expressed all the time; if they were, the bacterial cell would die. d. it does not cost them any energy to keep the gene expressed all the time.

ANS: B DIF: Easy REF: 8.7 OBJ: 8.7a Describe how and why a cell regulates expression of a virulence gene.

MSC: Understanding 37. The gene that codes for a protein involved in detoxifying an environmental toxin is only expressed in the presence of the toxin. A repressor protein controls transcription of the gene. The toxin mediates __________ of the gene by __________. a. induction; relieving repression imposed by the repressor b. induction; stimulating activation mediated by an activator c. repression; relieving repression imposed by the repressor d. repression; stimulating activation mediated by an activator ANS: A DIF: Moderate REF: 8.7 OBJ: 8.7b Outline the levels of gene regulation. Explain why it is useful to regulate gene expression at different levels.

MSC: Applying 38. PrfA protein is a global regulator of virulence genes in Listeria, a bacterium that can cause severe food poisoning. Below host body temperatures PrfA mRNA exists in a conformation that hides the ribosome binding site. Upon entry into a host and a rise in temperature, hydrogen bonds in the mRNA break, exposing the ribosome binding site. What level of gene regulation is seen here? a. changing the DNA sequence c. translation control b. transcription control d. posttranslational control ANS: C DIF: Moderate REF: 8.7 OBJ: 8.7a Describe how and why a cell regulates expression of a virulence gene.

MSC: Applying 39. In a typical two-component signal transduction system a. the sensor kinase senses the environment and the response regulator directly alters transcription. b. both the sensor kinase and the response regulator sense the environment. c. both the sensor kinase and the response regulator directly alter transcription. d. the sensor kinase directly alters transcription and the response regulator senses the environment.

ANS: A DIF: Easy REF: 8.7 OBJ: 8.7b Outline the levels of gene regulation. Explain why it is useful to regulate gene expression at different levels.

MSC: Understanding 40. In the lac operon, a mutation in the operator, LacO, that prevents repressor binding will cause which of the following changes compared to wild type cells? a. more expression of the lac operon when lactose is present b. more expression of the lac operon when lactose is absent c. less expression of the lac operon when lactose is present d. less expression of the lac operon when lactose is absent ANS: B

DIF: Difficult

REF: 8.7

OBJ: 8.7b Outline the levels of gene regulation. Explain why it is useful to regulate gene expression at different levels.

MSC: Analyzing 41. In a two-component signal transduction system the response regulator activity is altered via phosphorylation. This is an example of a. changing the DNA sequence. c. translation control. b. transcription control. d. posttranslational control.

ANS: D DIF: Easy REF: 8.7 OBJ: 8.7b Outline the levels of gene regulation. Explain why it is useful to regulate gene expression at different levels.

MSC: Applying 42. CASE HISTORY In Wichita, Kansas, a 20-year-old college student named Lillian visited the college health practitioner for a routine gynecological exam. Lillian’s periods had been regular, but she recently noted some spotting between periods. Her last menstrual period was four weeks prior. The practitioner asked Lillian whether she was sexually active. Lillian reported two male partners within the past six months.

She reported no vaginal discharge, dyspareunia (painful intercourse), genital lesions, or sores. Her breast, thyroid, and abdominal exam were within normal limits, as were her vital signs—blood pressure: 118/68, pulse: 74, respiration: 18, temperature: 37.1C (98.6F).

The genital exam revealed normal vulva and vagina. The practitioner found no cervical motion pain and no uterine or adnexal tenderness (areas that include and surround the fallopian tubes and ovaries). But Lillian’s cervix appeared inflamed and bled easily, with a purulent discharge coming from the cervical os (opening).

The practitioner performed nucleic acid amplification tests (NAATs) for Chlamydia trachomatis and Neisseria gonorrhoeae. Within a day, the NAAT results were positive for Chlamydia and negative for N. gonorrhoeae. Wet-mount microscopy revealed no pathogens but many WBCs (white blood cells). The diagnosis was confirmed as chlamydia infection, an infection reportable to the Centers for Disease Control and Prevention (CDC).

The practitioner prescribed doxycycline to clear up the infection. To curtail transmission, the practitioner asked Lillian to identify all her sexual partners for partner notification. Lillian recalled a third partner seven months earlier. The practitioner also recommended use of condoms to decrease further infections.

Doxycycline is an antibiotic that binds to the bacterial ribosome. This antibiotic interferes with the creating of proteins in bacterial cells by binding to the ribosome, which prevents a. DNA strands from being separated properly, preventing transcription. b. mRNA strands from being properly assembled from single-stranded DNA templates. c. mRNA from being properly read and translated into an amino acid sequence. d. completed proteins from being exported to the cell surface.

ANS: C DIF: Moderate REF: Case History 8.2 OBJ: 8.6b Describe the ribosomal steps of initiation, elongation, and termination. Explain how these steps may be targeted by antibacterial agents.

MSC: Applying COMPLETION 1. Transcription of genes starts at regions of the genome called ________.

ANS: promoters DIF: Moderate REF: 8.1 OBJ: 8.1a Describe the structure of a bacterial genome, and explain how it differs from a eukaryotic genome.

MSC: Remembering

2. Using the table below, it’s possible to determine that the amino acid sequence of the DNA template AACTATGCT is ________.

ANS: LEU-ILE-ARG DIF: Moderate REF: 8.3 OBJ: 8.3a Explain the different kinds of mutations and how they occur.

MSC: Applying 3. An enzyme that cuts the DNA phosphodiester backbone at a particular DNA sequence is called a ________.

ANS: restriction endonuclease or restriction enzyme; restriction endonuclease; restriction enzyme DIF: Easy REF: 8.4 OBJ: 8.4a Describe the use of plasmids, restriction enzymes, and gel electrophoresis to analyze DNA. MSC: Remembering 4. Proteins that assist the folding of newly formed proteins are known as ________.

ANS: chaperones; heat shock proteins DIF: Moderate REF: 8.6 OBJ: 8.6c Explain how proteins may require folding and secretion.

MSC: Remembering 5. A protein that affects the expression of many different genes is known as a ________.

ANS: global regulator DIF: Moderate REF: 8.7 OBJ: 8.7a Describe how and why a cell regulates expression of a virulence gene.

MSC: Remembering SHORT ANSWER 1. If DNA polymerase misincorporates a base, leading to a mismatch, how do repair enzymes distinguish the parental and daughter DNA strands to specifically fix the daughter strand?

ANS: Prior to replication both DNA strands are methylated. During synthesis the newly synthesized daughter strands are initially not methylated. Hence, it is the unmethylated strand that is repaired.

After a lag the daughter strands do become methylated. The semiconservative nature of DNA synthesis aids in this process.

DIF: Difficult REF: 8.2 OBJ: 8.2b Explain the steps of replication by DNA polymerase, including initiation, elongation, and termination.

MSC: Understanding 2. Why might the insertion or deletion of three base pairs in a gene be less harmful than the insertion or deletion of only one or two base pairs?

ANS: This is due to the triplet nature of codons. An insertion or deletion of three base pairs will add or remove a single amino acid from the final protein. Insertion or deletion of one or two base pairs will throw off the reading frame, and the rest of the protein downstream of the mutation will have different amino acids.

DIF: Difficult REF: 8.3 OBJ: 8.3a Explain the different kinds of mutations and how they occur.

MSC: Analyzing 3. During Sanger DNA sequencing, in addition to normal dNTPs used in cellular DNA synthesis, small amounts of modified DNA polymerase substrates are added to the reaction. How do these modified monomers differ from the normal dNTPs? ANS: First, the modified monomers are dideoxy nucleotide triphosphates (ddNTPs) that lack the 3OH group. This leads to chain termination. Second, each different ddNTP (ddATP, ddTTP, ddCTP, and ddGTP) has a different fluorescent label attached. This allows the identification of the ddNTP at the end of each synthesized fragment.

DIF: Difficult REF: 8.4 OBJ: 8.4c Explain the use of DNA hybridization and DNA sequencing technology.

MSC: Evaluating 4. Is the mRNA in the figure shown below a model of a bacterial mRNA or a eukaryotic mRNA? Please explain your rationale.

ANS: This mRNA represents a bacterial mRNA. I know this because there are two protein-coding regions within a single mRNA, part of an operon. Operons are rare to nonexistent in eukaryotes, and each spliced mRNA codes for a single protein—there are no multiple ribosome-binding sites in eukaryotic mRNAs. DIF: Moderate REF: 8.6 OBJ: 8.6a Explain the relationship between transcription and translation in bacteria.

MSC: Applying 5. Two common levels of regulation of protein activity are transcriptional control and posttranslational control. Please discuss the differences between the two in terms of speed of response and energy efficiency.

ANS: Transcriptional control is slower (the gene needs to be transcribed, the mRNA translated, and the protein correctly folded before protein activity) but is more energy-efficient because proteins are only made when they are needed. Posttranslational control is faster (the protein is already synthesized; it just needs a modification) but is less energy efficient because a protein might be made and degraded before it ever gets activated.

DIF: Difficult REF: 8.7 OBJ: 8.7b Outline the levels of gene regulation. Explain why it is useful to regulate gene expression at different levels.

MSC: Analyzing 6. CASE HISTORY In San Francisco, a 3-year-old boy named Luke was admitted to the hospital after an abrupt onset of fever and a generalized seizure. The boy’s cerebrospinal fluid was normal, and he had a normal chest radiograph, but his white blood cell count was 20,000/mm3 (normal is 5,000–10,000), with 85% polymorphonuclear leukocytes (PMns). Luke’s blood culture revealed bacteremia (bacteria in the blood). The bacteria were identified as “nontypeable” Haemophilus influenzae bacteria. The nontypeable H. influenzae strain was beta-lactamase-positive (expressed an enzyme to inactivate penicillin G, ampicillin, and amoxicillin) but proved sensitive to cefixime, a third-generation cephalosporin.

The diagnosis surprised the boy’s two fathers. They showed the doctor Luke’s full record of immunizations and booster shots, including the standard DTaP (diphtheria, tetanus, and pertussis), hepatitis B, pneumococcus, and Haemophilus influenzae b (Hib). Why was Luke not protected by the Hib vaccine? The doctor explained that the Hib vaccine protected only from H. influenzae type b, the most common virulent strain—but not the only virulent strain. Six strains, or serotypes, a through f, are “typed” based on the type of polysaccharide capsule surrounding the cell envelope. The Hib vaccine targets capsule type b. But some variant strains of H. influenzae, called “nontypeable,” lack a capsule. These strains can be identified on the basis of other properties, such as enzyme activities, but they are unaffected by the vaccine. Fortunately, after seven days of intravenous antibiotic, Luke recovered fully.

The H. influenzae strain infecting Luke was beta-lactamase positive. Would the cell be likely to express the gene for this enzyme at all times? Describe one mechanism by which the cell could regulate the expression of this enzyme.

ANS: No, in order to make the best use of available resources, beta-lactamase enzymes used to resist an antibiotic might only be expressed in the presence of that antibiotic. Several mechanisms described in the chapter could be mentioned, including removal of a repressor governing this gene when it binds a beta lactam ring.

DIF: Difficult REF: Case History 8.1 OBJ: 8.7a Describe how and why a cell regulates expression of a virulence gene.

MSC: Applying 7. CASE HISTORY Tina, a 33-year-old store clerk from Peoria, Illinois, had her first dental exam in five years. She told the hygienist that her gums hurt and that stains appeared on her pillow where her jaw had rested. She also told the hygienist that she did not smoke or drink.

The hygienist found that Tina’s gums were swollen and bled upon probing. The gums had receded from Tina’s teeth, forming pockets about 5mm deep, and X-rays revealed some loss of bone.

Tina then saw the dentist, who told her she had periodontitis, inflammatory disease of the gums and bone supporting the teeth. Periodontitis is caused by dental plaque, a biofilm of mixed bacterial species that grow on the teeth. Without regular oral hygiene, the biofilm grows beneath the gum and eventually causes loss of teeth.

Tina expressed surprise, as she thought that only elderly people suffered gum disease. The dentist asked her again whether she smoked, perhaps two packs a day. Tina denied smoking that much but admitted to one pack a day. The dentist told her that smoking is a common factor in early gum disease, as are diabetes and genetic susceptibility. Under predisposing conditions, many different kinds of bacteria can cause gum disease.

To determine the bacterial species causing Tina’s periodontitis, the dentist ordered a DNA test.

The DNA test works by polymerase chain reaction (PCR), a technique in which a short piece of DNA is amplified (copied many times), making it possible to read the sequence of DNA base pairs. The DNA sequence reveals the bacterial species. Tina’s DNA test revealed Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, two Gram-negative anaerobes that are sensitive to metronidazole and amoxicillin, respectively.

The DNA test enabled the dentist to target the most effective antibiotics for Tina’s condition. The dentist also enrolled Tina in a smoking cessation program.

Following amplification of the bacterial DNA from Tina’s sample, one of the ways the bacteria involved may be identified is via sequencing of the amplified fragment of DNA. Explain how this process works and how it can be used to identify bacteria.

ANS: The sequence of a template DNA can be read by using reactions of DNA synthesis by a DNA polymerase. Each reaction includes dNTPs with a small amount of fluorescent-tagged chainterminating dideoxy NTP for each of the four nucleotides. The reactions generate patterns of DNA fragments terminated at each of the four nucleotides; the mixtures are separated by electrophoresis and detected by a laser. The sequence can then be compared to known sequences to yield a species-level identification.

DIF: Moderate REF: Case History Chapter 8 Intro OBJ: 8.4c Explain the use of DNA hybridization and DNA sequencing technology.

MSC: Applying

Chapter 09: Bacterial Genomes and Evolution LEARNING OBJECTIVES 9.1a Explain how genetic information moves between bacteria by transformation, phage-mediated transduction,and conjugation.

9.1b Describe how DNA molecules recombine by homologous recombination and site-specific recombination.

9.1c Describe how gene mobility and DNA recombination lead to the emergence of new pathogens.

9.2a Describe how all life originated from microbes, how life-forms evolved over time, and how species continue to evolve.

9.2b Explain how microbial genomes change via processes of random mutation and natural selection.

9.2c Explain how a molecular clock works to measure phylogeny, and describe the key attributes of a useful molecular clock gene.

9.2d Describe the three domains of life.

9.3a Explain how fitness of a trait depends on the environment and how environment-dependent fitness leads to the evolution of antibiotic resistance in pathogens.

9.3b Describe the evolution of endosymbiosis between a host cell and an internalized partner organism.

9.4a Explain how bioinformatic analysis helps reveal the pathogenesis and physiology of an emerging pathogen.

9.4b Describe how gene duplication leads to different kinds of homologous genes, including orthologs and paralogs.

9.5a Describe how we define distinct species of bacteria, and explain why the definition of species is problematic.

9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MULTIPLE CHOICE 1. Griffith’s observations from his experiments infecting mice with smooth- and rough-strain Streptococcus pneumoniae were later found to be due to a. conjugation. c. transduction. b. transposition. d. transformation.

ANS: D DIF: Moderate REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Understanding 2. Generational passing of genes from parent to offspring is called a. vertical transfer. c. transduction. b. horizontal transfer. d. transformation.

ANS: A DIF: Easy REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Understanding 3. Which type of horizontal transfer requires intimate cell-cell contact? a. transposition c. transduction

b. conjugation

d. transformation

ANS: B DIF: Easy REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Understanding 4. Why might an organism transform DNA that is homologous to its own? a. as a food source b. to obtain new DNA c. to repair its own damaged genome d. Organisms are not capable of transforming homologous DNA. ANS: C DIF: Moderate REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Understanding 5. What specifically is passed from the donor cell to the recipient cell during conjugation? a. single-stranded DNA c. protein subunits b. double-stranded DNA d. F factor pilus ANS: A DIF: Moderate REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Understanding 6. Which of the following is NOT a step in the transduction process? a. The DNA phage enters a bacterial cell by endocytosis. b. The phage DNA commandeers host protein synthesis machinery. c. The phage uses host cell DNA replication machinery. d. Completed phage particles are released into the environment by lysing.

ANS: A DIF: Easy REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Remembering 7. Which of the following forms of horizontal gene transfer involves a prophage? a. generalized transduction b. specialized transduction c. F-factor conjugation d. competence-mediated transformation ANS: B DIF: Easy REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Remembering 8. How do bacteria protect their own DNA from restriction enzymes? a. restriction digestion b. methylation of target sequences c. generalized recombination d. site-specific recombination ANS: B DIF: Moderate REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Applying 9. A protein called integrase is encoded by ________ and allows for site-specific recombination in C. diphtheria.

a. E. coli b. S. pneumoniae

c. C. diphtheria d. beta phage

ANS: D DIF: Moderate REF: 9.1 OBJ: 9.1b Describe how DNA molecules recombine by homologous recombination and site-specific recombination.

MSC: Understanding 10. The elements that form living organisms first originated from a. viruses. c. water. b. stardust. d. the oceans.

ANS: B DIF: Easy REF: 9.2 OBJ: 9.2a Describe how all life originated from microbes, how life-forms evolved over time, and how species continue to evolve.

MSC: Remembering 11. Which of the following does NOT lead to divergence? a. fossilization c. transposition b. mutations d. transduction ANS: A DIF: Moderate REF: 9.2 OBJ: 9.2b Explain how microbial genomes change via processes of random mutation and natural selection.

MSC: Applying 12. Which of the following is NOT a good scenario for a molecular clock? a. The gene used has the same function across all species being compared. b. The generation time is the same for all species being compared. c. The average mutation rate is constant among species. d. The gene used is nonessential.

ANS: D DIF: Moderate REF: 9.2 OBJ: 9.2c Explain how a molecular clock works to measure phylogeny, and describe the key attributes of a useful molecular clock gene.

MSC: Understanding 13. If the mutation rate is not the same for all species being compared using a molecular clock, what does a phylogenetic tree demonstrate? a. the time since two species diverged from a common ancestor b. the evolutionary distance between two species c. the generation time for species d. the induced mutation frequency between two species ANS: B DIF: Difficult REF: 9.2 OBJ: 9.2c Explain how a molecular clock works to measure phylogeny, and describe the key attributes of a useful molecular clock gene.

MSC: Analyzing 14. Examine the figure shown below. Which organism does NOT share the same common ancestor as Escherichia and Erwinia carotovora?

a. Sodalis glossinidius b. Photorhabdus luminescens

c. Klebsiella d. Salmonella

ANS: A DIF: Moderate REF: 9.2 OBJ: 9.2c Explain how a molecular clock works to measure phylogeny, and describe the key attributes of a useful molecular clock gene.

MSC: Applying 15. Which of the following domains of life contain ether linkages in their membranes? a. viral c. bacteria b. eukarya d. archaea ANS: D DIF: Moderate REF: 9.2 OBJ: 9.2d Describe the three domains of life.

MSC: Understanding

16. Which of the following is NOT a domain of life? a. virus c. bacteria b. eukarya d. archaea ANS: A DIF: Easy REF: 9.2 OBJ: 9.2d Describe the three domains of life.

MSC: Understanding

17. Meaningful evolution occurs when a. a changed trait affects survival. b. a changed trait gives an organism an advantage. c. a changed trait gives an organism a disadvantage. d. environmental factors change.

ANS: A DIF: Moderate REF: 9.3 OBJ: 9.3a Explain how fitness of a trait depends on the environment and how environmentdependent fitness leads to the evolution of antibiotic resistance in pathogens.

MSC: Understanding 18. Examine the figure shown below. What happened to transform the original MRSA isolate into the small-colony variant?

a. evolution b. natural selection

c. speciation d. fitness reduction

ANS: B DIF: Moderate REF: 9.3 OBJ: 9.3a Explain how fitness of a trait depends on the environment and how environmentdependent fitness leads to the evolution of antibiotic resistance in pathogens.

MSC: Applying 19. Examine the figure shown below. Which of the following correctly describes how the two organisms pictured would fare if grown in an environment without antibiotics?

a. b. c. d.

The small-colony variant would outcompete the original isolate.

The small-colony variant would grow better than the original isolate.

The original isolate would outcompete the small-colony variant.

Neither organism would grow in this condition.

ANS: C DIF: Moderate REF: 9.3 OBJ: 9.3a Explain how fitness of a trait depends on the environment and how environmentdependent fitness leads to the evolution of antibiotic resistance in pathogens.

MSC: Applying 20. What is most important for determining the fitness of one organism versus another? a. reproductive strategy c. genetic composition b. generation time d. the environment ANS: D DIF: Easy REF: 9.3 OBJ: 9.3a Explain how fitness of a trait depends on the environment and how environmentdependent fitness leads to the evolution of antibiotic resistance in pathogens.

MSC: Remembering 21. Without selective pressure, a species is at risk of experiencing a. random mutation. c. reductive evolution. b. natural selection. d. endosymbiosis.

ANS: C DIF: Easy REF: 9.3 OBJ: 9.3b Describe the evolution of endosymbiosis between a host cell and an internalized partner organism.

MSC: Understanding 22. Wolbachia appears to be developing into a(n) ________ of its host. a. mitochondria c. organelle b. chloroplast d. endosymbiont ANS: C DIF: Easy REF: 9.3 OBJ: 9.3b Describe the evolution of endosymbiosis between a host cell and an internalized partner organism.

MSC: Remembering 23. Antibiotics can be used to treat the nematode cause of filarial disease because antibiotics a. kill off Wolbachia, which is important for the embryonic development of the worm. b. always kill off nematodes. c. stimulate the immune system to more effectively fight off the nematodes. d. are not used to treat filarial disease.

ANS: A DIF: Moderate REF: 9.3 OBJ: 9.3b Describe the evolution of endosymbiosis between a host cell and an internalized partner organism.

MSC: Understanding 24. Which of the following can result in degenerative evolution? a. natural selection c. fitness reduction b. endosymbiosis d. parasitism ANS: B DIF: Moderate REF: 9.3 OBJ: 9.3b Describe the evolution of endosymbiosis between a host cell and an internalized partner organism.

MSC: Applying 25. The traits of the hidden microbiota of humans can be predicted by analyzing a. cellular structure. c. microscopic appearance. b. DNA sequences. d. growth patterns.

ANS: B DIF: Easy REF: 9.4 OBJ: 9.4a Explain how bioinformatic analysis helps reveal the pathogenesis and physiology of an emerging pathogen. MSC: Remembering

26. Genes for transfer RNA can be predicted through a. amino acid sequence similarity. b. protein function prediction. c. gene function prediction. d. conservation over vast phylogenetic distances.

ANS: D DIF: Moderate REF: 9.4 OBJ: 9.4a Explain how bioinformatic analysis helps reveal the pathogenesis and physiology of an emerging pathogen. MSC: Understanding 27. Which of the following is NOT a characteristic of an open reading frame? a. It has a DNA sequence long enough to encode an amino acid sequence of at least 50. b. It begins with a translation start codon. c. It ends with a translation termination codon. d. It contains a promoter sequence.

ANS: D DIF: Moderate REF: 9.4 OBJ: 9.4a Explain how bioinformatic analysis helps reveal the pathogenesis and physiology of an emerging pathogen. MSC: Understanding 28. How does one begin to identify a predicted protein? a. experimentally determine its amino acid sequence b. compare its predicted amino acid or DNA sequence to that of known proteins c. analyze its RNA sequence d. determine the sequence of its paralog ANS: B DIF: Moderate REF: 9.4 OBJ: 9.4a Explain how bioinformatic analysis helps reveal the pathogenesis and physiology of an emerging pathogen. MSC: Applying 29. The gene proV codes for an ABC transport protein responsible for bringing proline or glycine betaine into the cell in response to osmotic stress. This gene serves a similar function in Salmonella and E. coli. This is an example of ________ genes. a. nonprotein coding c. ortholog b. paralog d. degenerate ANS: C DIF: Moderate REF: 9.4 OBJ: 9.4b Describe how gene duplication leads to different kinds of homologous genes, including orthologs and paralogs.

MSC: Applying 30. The marine organism Chromohalobacter salexigens contains two homologous genes responsible for the conversion of -ketoglutarate to succinyl-CoA. A third gene contains a similar sequence and appears to have evolved from the other two genes to complete a different function. This is an example of ________ genes. a. paralog c. degenerate b. ortholog d. nonfunctional ANS: A DIF: Moderate REF: 9.4 OBJ: 9.4b Describe how gene duplication leads to different kinds of homologous genes, including orthologs and paralogs.

MSC: Applying 31. Which of the following is an example of functional genomics? a. predicting the function of genes in Haemophilus influenzae from the genomic sequence b. transforming antibiotic resistance genes into MRSA c. measuring the pathogenesis of Corynebacterium diphtheria

d. eliminating the presence of Wolbachia endosymbionts ANS: A DIF: Moderate REF: 9.4 OBJ: 9.4b Describe how gene duplication leads to different kinds of homologous genes, including orthologs and paralogs.

MSC: Applying 32. Which of the following can be used to provide evidence of horizontal gene transfer? a. comparison of GC content b. protein sequence similarity c. cell structure modification d. plasmid curing ANS: A DIF: Easy REF: 9.4 OBJ: 9.4b Describe how gene duplication leads to different kinds of homologous genes, including orthologs and paralogs.

MSC: Understanding 33. Which is NOT an agreed-upon characteristic for microorganism species determination? a. conjugation similarity c. DNA relatedness b. phylogeny d. ecology ANS: A DIF: Moderate REF: 9.5 OBJ: 9.5a Describe how we define distinct species of bacteria, and explain why the definition of species is problematic.

MSC: Understanding 34. The Enterobacteriaceae family is taxonomically considered a(n) a. classification. c. identification. b. nomenclature. d. homolog.

ANS: A DIF: Moderate REF: 9.5 OBJ: 9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MSC: Applying 35. Serratia marcescens is taxonomically considered a a. homolog. c. nomenclature. b. identification. d. classification.

ANS: C DIF: Moderate REF: 9.5 OBJ: 9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MSC: Applying 36. Which is NOT a useful way to identify a microorganism? a. sequencing its genome b. phenotypic trait analysis c. microscopic observation alone d. phylogenetic analysis ANS: C DIF: Moderate REF: 9.5 OBJ: 9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MSC: Understanding 37. What is a DISADVANTAGE of a probabilistic indicator compared to a dichotomous key? a. more time-consuming b. less applicable to microorganisms isolated in a clinical setting

c. more redundancy leading to fewer errors d. There are no scientific disadvantages to using a probabilistic indicator.

ANS: D DIF: Moderate REF: 9.5 OBJ: 9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MSC: Understanding 38. What is the best option for characterizing a completely unknown organism? a. DNA sequencing b. dichotomous key c. probabilistic indicator d. phylogenetic tree construction ANS: A DIF: Easy REF: 9.5 OBJ: 9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MSC: Remembering 39. Renaming Pasteurella pestis to Yersinia pestis alters the ________ of the organism. a. classification c. identification b. nomenclature d. homology ANS: B DIF: Moderate REF: 9.5 OBJ: 9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MSC: Understanding 40. Consider the dichotomous key shown below. What do the numbered organisms (0961, 0914, and 021N) require?

a. homology b. classification

c. nomenclature d. identification

ANS: B DIF: Moderate REF: 9.5 OBJ: 9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MSC: Understanding 41. CASE HISTORY

Nine-month-old Eva had 12 clinic visits over a seven-month period due to runny nose and/or ear infections. During each episode, nasopharyngeal swabs were obtained for bacterial culture and Streptococcus pneumoniae was obtained. Although all the infections were resolved with antibiotics, scientists gained insight into pathogen evolution by seeing how the isolates compared. Each isolate was first analyzed for seven genes that can indicate strain variability, a process called multilocus sequence typing (MLST). The lab found two MLST types, indicating that the patient was infected with two divergent strains of S. pneumoniae. However, when the complete genomes of several of the isolates were sequenced and compared, four different genotypic strains were identified, all of which evolved as a result of 16 distinct recombination events between strains. Curiously, the technicians noticed that some recombined sequences did not seem to come from either of the two primary coinfecting strains. It appeared that this new DNA came from uncultured and undetected strains of S. pneumoniae that had colonized Eva’s throat at one time or another. Horizontal gene transfers (transformation) between the undetected and detected isolates appear to have produced the new recombined strains of S. pneumoniae. The genome sequence data clearly support the idea that S. pneumoniae evolution is characterized by high rates of horizontal gene transfer and recombination.

The scientists concluded that this and other related bacterial species use horizontal gene transfer to defeat the adaptive immunity of individual hosts, possibly explaining Eva’s recurring infections. These types of bioinformatic comparisons suggest that horizontal gene transfers that produce most of the genetic variation pathogens develop while persisting within a host.

Which of the following best explains Eva’s recurring Streptococcus pneumoniae ear infections? a. The strains with which she was infected were antibiotic resistant due to horizontal gene transfer. b. Because she is a baby, she has low immunity. c. The strains with which she was infected varied in antigen production due to horizontal gene transfer. d. The strains with which she was infected were highly virulent due to horizontal gene transfer.

ANS: C DIF: Moderate REF: Case History 9.2 OBJ: 9.4a Explain how bioinformatic analysis helps reveal the pathogenesis and physiology of an emerging pathogen. MSC: Applying COMPLETION 1. The enzyme ________ is important for generalized recombination.

ANS: RecA DIF: Easy REF: 9.1 OBJ: 9.1b Describe how DNA molecules recombine by homologous recombination and site-specific recombination.

MSC: Remembering 2. Ancient ________ give evidence to the fact that all life originated from microorganisms.

ANS: microfossils DIF: Moderate REF: 9.2 OBJ: 9.2a Describe how all life originated from microbes, how life-forms evolved over time, and how species continue to evolve.

MSC: Understanding 3. The ________ gene was used as a molecular clock to reveal the divergence of three domains of life.

ANS: 16S rRNA; 16S

DIF: Easy REF: 9.2 OBJ: 9.2c Explain how a molecular clock works to measure phylogeny, and describe the key attributes of a useful molecular clock gene.

MSC: Remembering 4. A ________ relationship develops between endosymbionts and their hosts.

ANS: mutualistic DIF: Easy REF: 9.3 OBJ: 9.3b Describe the evolution of endosymbiosis between a host cell and an internalized partner organism.

MSC: Understanding 5. ________ is important for analyzing and comparing the genomic sequences of organisms.

ANS: Annotation DIF: Easy REF: 9.4 OBJ: 9.4a Explain how bioinformatic analysis helps reveal the pathogenesis and physiology of an emerging pathogen. MSC: Understanding SHORT ANSWER 1. Would transformation be possible for an organism that does not produce nucleases? Explain.

ANS: The transformation process requires one strand of the DNA being transformed to be degraded by a nuclease prior to entry into the cell while the complementary strand serves as a template. The process would not be possible if the organism did not produce a nuclease, as the double-stranded DNA is too large to transport into the cell.

DIF: Difficult REF: 9.1 OBJ: 9.1a Explain how genetic information moves between bacteria by transformation, phagemediated transduction, and conjugation.

MSC: Evaluating 2. Describe how horizontal gene transfer could lead to the emergence of a new bacterial pathogen.

ANS: A variety of answers are possible but should include some mention about how horizontal gene transfer allows for an organism to pick up new genes; if these genes give an organism a new ability or increased fitness, it could theoretically create a new, stronger bacterial pathogen.

DIF: Difficult REF: 9.1 OBJ: 9.1c Describe how gene mobility and DNA recombination lead to the emergence of new pathogens.

MSC: Analyzing 3. Create an example that shows how random mutations lead to natural selection and divergence of organisms.

ANS: A variety of answers are possible as long as the example describes random mutations resulting in increased fitness or reproductive success of organisms, leading to natural selection of those organisms over others that do not have the mutations and divergence of organisms.

DIF: Difficult REF: 9.2 OBJ: 9.2b Explain how microbial genomes change via processes of random mutation and natural selection.

MSC: Evaluating 4. For each domain of life, list three characteristics that distinguish it from the other two domains.

ANS: A variety of answers are possible so long as each clearly distinguishes one domain from the other two.

DIF: Moderate MSC: Applying

REF: 9.2

OBJ: 9.2d Describe the three domains of life.

5. Explain how natural selection quickly leads to antibiotic resistance.

ANS: Exposure to antibiotics eliminates all organisms except those that are resistant. Continuous treatment will select for those organisms alone that are resistant, leading to a larger proportion of resistant organisms that can then spread the genes that allow for their resistance to other organisms.

DIF: Moderate REF: 9.3 OBJ: 9.3a Explain how fitness of a trait depends on the environment and how environmentdependent fitness leads to the evolution of antibiotic resistance in pathogens.

MSC: Applying 6. Describe how gene duplication leads to paralogs.

ANS: Gene duplication is followed by the mutation of one gene to carry out a different function, leading to a paralog.

DIF: Easy REF: 9.4 OBJ: 9.4b Describe how gene duplication leads to different kinds of homologous genes, including orthologs and paralogs.

MSC: Understanding 7. What are two reasons why the definition of a species is problematic for bacteria?

ANS: Answers include asexual reproduction and horizontal gene transfer. Variations in the quantitative measures of genetic sequence divergence among different organisms is also a possible answer.

DIF: Moderate REF: 9.5 OBJ: 9.5a Describe how we define distinct species of bacteria, and explain why the definition of species is problematic.

MSC: Understanding 8. Using the dichotomous key shown below, determine the identity of an organism isolated in pure culture given the following characteristics: Filament smoothly curved Sheath No branching

ANS: Thiotrix II DIF: Difficult REF: 9.5 OBJ: 9.5b Explain how a microbe is identified, and describe the relative advantages and limitations of a dichotomous key, as compared with a probabilistic indicator.

MSC: Analyzing 9. CASE HISTORY

Harrison was a 73-year-old man with kidney failure. He was admitted to the hospital with fever and hypotension, both of which are symptoms of bacteremia. When bacteria from Harrison’s blood were grown on horse blood agar, it showed colonies typical of methicillin-resistant Staphylococcus aureus (MRSA) and confirmed the diagnosis of bacteremia. Further investigation uncovered his home dialysis line as the source of MRSA. He was treated with intravenous vancomycin (an antibiotic that targets cell wall synthesis), but the bacteremia persisted. The bacteria were tested and found to be partly resistant to vancomycin, though sensitive to rifampin (which targets RNA polymerase), ciprofloxacin (which targets DNA gyrase), and linezolid (which targets protein synthesis). The vancomycin was discontinued, and therapy was begun with rifampin, ciprofloxacin, and linezolid. Harrison’s symptoms improved, but within three weeks the bacteremia returned. Bacteria cultured from his blood now showed resistance to rifampin and ciprofloxacin. Linezolid was administered alone for six weeks, but five days after linezolid treatment ended, the bacteremia recurred. Linezolid was administered again, for another six weeks. Then a new blood culture revealed a form of MRSA with small colonies. The small-colony variant was partly resistant to linezolid while fully resistant to all the other antibiotics.

Harrison was now treated with trimethoprim-sulfamethoxazole. These final antibiotics had to be administered indefinitely, as they could not fully eliminate MRSA from Harrison’s system.

A laboratory technician cultures the small-colony form of MRSA for 100 generations on agar media without antibiotics, selecting the largest colony for passage at each generation. Would you predict the 100th generation would be more or less resistant to linezolid than the isolate from Harrison’s highly resistant infection?

ANS: The 100th generation would be less resistant to linezolid. In an environment in which rapid growth is selected for rather than antibiotic resistance, the nonresistant phenotype will become more prominent.

DIF: Difficult REF: Case History 9.1 OBJ: 9.3b Describe the evolution of endosymbiosis between a host cell and an internalized partner organism.

MSC: Evaluating 10. CASE HISTORY Nine-month-old Eva had 12 clinic visits over a seven-month period due to runny nose and/or ear infections. During each episode, nasopharyngeal swabs were obtained for bacterial culture and Streptococcus pneumoniae was obtained. Although all the infections were resolved with antibiotics, scientists gained insight into pathogen evolution by seeing how the isolates compared. Each isolate was first analyzed for seven genes that can indicate strain variability, a process called multilocus sequence typing (MLST). The lab found two MLST types, indicating that the patient was infected with two divergent strains of S. pneumoniae. However, when the complete genomes of several of the isolates were sequenced and compared, four different genotypic strains were identified, all of which evolved as a result of 16 distinct recombination events between strains. Curiously, the technicians noticed that some recombined sequences did not seem to come from either of the two primary coinfecting strains. It appeared that this new DNA came from uncultured and undetected strains of S. pneumoniae that had colonized Eva’s throat at one time or another. Horizontal gene transfers (transformation) between the undetected and detected isolates appear to have produced the new recombined strains of S. pneumoniae. The genome sequence data clearly support the idea that S. pneumoniae evolution is characterized by high rates of horizontal gene transfer and recombination.

The scientists concluded that this and other related bacterial species use horizontal gene transfer to defeat the adaptive immunity of individual hosts, possibly explaining Eva’s recurring infections. These types of bioinformatic comparisons suggest that horizontal gene transfers that produce most of the genetic variation pathogens develop while persisting within a host.

Could antibiotic resistance from one strain of Streptococcus pneumoniae to another occur by transformation?

ANS: Though none of the strains with which Eva was infected appear to be resistant (she was treated successfully with antibiotics for each infection), many recombination events occurred. In the event an antibiotic-resistant strain had been present, even transiently, it is possible that some of the genes transferred could be related to antibiotic resistance. Gene transfer also occurs by other mechanisms, some of which are more likely in practice to be associated with the transfer of antimicrobial resistance genes, for example conjugation.

DIF: Difficult REF: 9.2 OBJ: 9.1c Describe how gene mobility and DNA recombination lead to the emergence of new pathogens.

MSC: Evaluating

Chapter 10: Bacterial Diversity LEARNING OBJECTIVES 10.1a Distinguish among five major groups of bacteria: Gram-positive bacteria, Gram-negative bacteria,spirochetes, Cyanobacteria, and Chlamydias.

10.1b Describe the positive roles of bacteria in ecosystems.

10.1c Describe how new pathogens emerge to cause new diseases.

10.2a Describe the traits that enable Firmicutes to survive dryness and persist for long periods.

10.2b Describe how diverse Actinobacteria have both positive and negative influences on human health.

10.3a Describe the diverse environmental roles of Proteobacteria.

10.3b Identify the diseases caused by diverse Gram-negative bacteria.

10.4a Describe the unique coiled cells of the spirochetes.

10.4b Identify spirochetes that cause important human diseases.

10.4c Identify spirochetes that grow as environmental symbionts.

10.5a Explain the key environmental contributions of cyanobacteria.

10.5b Describe different forms of marine cyanobacteria.

10.6a Describe the cell cycle of Chlamydias.

10.6b Describe the diseases caused by Chlamydias.

MULTIPLE CHOICE 1. Which of the following is used to measure the relatedness of organisms? a. fossil records of bacteria b. sequencing and comparing ribosomal RNA c. comparing phenotypic differences between cells d. determining which bacteria are able to interbreed ANS: B DIF: Easy REF: 10.1 OBJ: 10.1a Distinguish among five major groups of bacteria: Gram-positive bacteria, Gram-negative bacteria, spirochetes, Cyanobacteria, and Chlamydias.

MSC: Understanding 2. Using the figure shown below, which genus is most closely related to Chlamydia?

a. Treponema b. Verrucomicrobium

c. Clostridium d. Pseudomonas

ANS: B DIF: Easy REF: 10.1 OBJ: 10.1a Distinguish among five major groups of bacteria: Gram-positive bacteria, Gram-negative bacteria, spirochetes, Cyanobacteria, and Chlamydias.

MSC: Applying 3. An environmental sample from the ocean contains phototrophic bacteria that produce oxygen. How would you classify these bacteria? a. Information about the cell wall would be required to determine whether these bacteria are Gram positive or Gram negative. b. These bacteria must be cyanobacteria based on their production of oxygen. c. It is highly probable that these bacteria are Gram-negative bacteria based on their presence in a marine environment. d. These bacteria must be Chlamydia found within unicellular organisms.

ANS: B DIF: Easy REF: 10.1 OBJ: 10.1a Distinguish among five major groups of bacteria: Gram-positive bacteria, Gram-negative bacteria, spirochetes, Cyanobacteria, and Chlamydias.

MSC: Analyzing 4. An isolate that ________ likely indicates a Gram-positive bacterium and excludes other bacteria. a. is found in a soil sample c. is an intracellular pathogen b. forms dormant endospores d. produces oxygen ANS: B DIF: Moderate REF: 10.1 OBJ: 10.1a Distinguish among five major groups of bacteria: Gram-positive bacteria, Gram-negative bacteria, spirochetes, Cyanobacteria, and Chlamydias.

MSC: Analyzing 5. Which of the following is NOT an example of a positive role that bacteria play in an ecosystem? a. fixation of carbon dioxide into biomass b. oxygen production c. breakdown of pollutants d. pathogenic relationship with humans ANS: D

DIF: Easy

REF: 10.1

OBJ: 10.1b Describe the positive roles of bacteria in ecosystems.

MSC: Understanding 6. A bacterial disease previously known to only infect dogs begins to cause respiratory infections in humans who are in close contact with infected dogs. Which of the following is the most likely explanation for the emergence of this new human pathogen? a. The genome of the bacterium changed through horizontal gene transfer within the microbiota of the dog. b. There was a mutation in the human genome that allowed the bacterium to attack human cells more vigorously. c. The bacterium became infected by a mutation-inducing virus transmitted through flea bites on the dog. d. The genome of the bacterium changed through vertical gene transfer within the microbiota of the dog.

ANS: A DIF: Difficult REF: 10.1 OBJ: 10.1c Describe how new pathogens emerge to cause new diseases.

MSC: Analyzing 7. A soil sample taken shortly after a large chemical spill has occurred reveals only a few living bacteria.

Six months later, a second sample from the same site reveals only a single bacterial species, which is present in high numbers. What may have caused this change? a. This bacterial species was most likely left at the site by the original sampling equipment. b. Animals passing through the area most likely deposited fecal matter full of microbiota. c. The bacterial species found in high numbers contains at least one gene that provides a competitive advantage. d. The single bacterial species must have been within the gut of a shelter species.

ANS: C DIF: Difficult REF: 10.1 OBJ: 10.1c Describe how new pathogens emerge to cause new diseases.

MSC: Evaluating 8. Which of the following characteristics is associated with bacteria in the phylum Firmicutes and most likely helps them survive dryness? a. a thick waxy coat that excludes Gram stain b. horizontal gene transfer between two cells c. thick cell walls with multiple layers of peptidoglycan d. they can all form endospores ANS: C DIF: Easy REF: 10.2 OBJ: 10.2a Describe the traits that enable Firmicutes to survive dryness and persist for long periods.

MSC: Applying 9. Which of the following most likely preceded the division shown below?

a. b. c. d.

Nutrients became depleted.

Environmental temperature decreased to 10oC. Nutrient availability increased.

Environmental moisture increased.

ANS: A DIF: Easy REF: 10.2 OBJ: 10.2a Describe the traits that enable Firmicutes to survive dryness and persist for long periods.

MSC: Understanding 10. How can some Firmicutes persist in the environment for centuries? a. Their unique cell shapes reduce surface area to prevent desiccation. b. They form dormant endospores that remain viable for long periods of time. c. They are able to slow their metabolism in vegetative cells when nutrients are depleted. d. They produce a thick waxy coating when the environment becomes dry.

ANS: B DIF: Moderate REF: 10.2 OBJ: 10.2a Describe the traits that enable Firmicutes to survive dryness and persist for long periods.

MSC: Applying 11. The mycelia of Streptomyces and other actinomycetes are known to produce a. lactic acid. c. antibiotics. b. endospores. d. statins.

ANS: C DIF: Easy REF: 10.2 OBJ: 10.2b Describe how diverse Actinobacteria have both positive and negative influences on human health.

MSC: Remembering 12. Which one of the following diseases is NOT caused by Actinobacteria? a. tuberculosis c. diphtheria b. leprosy d. botulism ANS: D DIF: Easy REF: 10.2 OBJ: 10.2b Describe how diverse Actinobacteria have both positive and negative influences on

human health.

MSC: Remembering

13. Your friend Miguel discovers a new bacterium and uses this bacterium to develop a popular new cheese with a taste similar to Swiss cheese. He is not willing to share his secret to success, but you suspect the bacteria he is using is a(n) a. Firmicutes. c. cyanobacteria. b. Actinobacteria. d. spirochete.

ANS: B DIF: Moderate REF: 10.2 OBJ: 10.2b Describe how diverse Actinobacteria have both positive and negative influences on human health.

MSC: Applying 14. Which of the following statements most accurately describes Actinobacteria? a. Most have an acid-fast property associated with unusual cell wall lipids that also protect them from host defenses and antibiotics. b. All Actinobacteria are considered to be pathogens in humans or other animals. c. Most Actinobacteria are nonpathogenic in humans but cause serious diseases in other animals. d. Many Actinobacteria produce endospores that allow them to survive for thousands of years.

ANS: A DIF: Moderate REF: 10.2 OBJ: 10.2b Describe how diverse Actinobacteria have both positive and negative influences on human health.

MSC: Understanding 15. Which of the following does NOT accurately describe Pseudomonas aeruginosa? a. causes opportunist infections in human surgical wounds b. may form biofilms on pulmonary lining of cystic fibrosis patients c. commonly grows in soil as a decomposer d. may infect fleas, which transmit P. aeruginosa to humans ANS: D DIF: Moderate REF: 10.3 OBJ: 10.3b Identify the diseases caused by diverse Gram-negative bacteria.

MSC: Applying 16. It is possible for humans to use some Proteobacteria, such as Geobacter species, to generate electricity because Geobacter species a. use lipopolysaccharide, or LPS, within their outer membrane to store energy that can be harnessed. b. transfer electrons to electrodes in fuel cells because they transfer electrons to iron or magnesium. c. are heavily flagellated and display swarming behavior that generates electricity. d. produce gases during fermentation of carbohydrates, and these gases are used in fuel cells.

ANS: B DIF: Difficult REF: 10.3 OBJ: 10.3a Describe the diverse environmental roles of Proteobacteria.

MSC: Applying 17. Which of the following species causes an illness that can be prevented by immunization? a. Bordetella pertussis c. Vibrio cholera b. Neisseria gonorrhoeae d. Helicobacter pylori ANS: A DIF: Easy REF: 10.3 OBJ: 10.3b Identify the diseases caused by diverse Gram-negative bacteria.

MSC: Applying

18. Which of the following pathogens would most likely thrive in a growth media with an extremely low pH? a. Haemophilus influenzae c. Moraxella catarrhalis b. Neisseria gonorrhoeae d. Helicobacter pylori ANS: D DIF: Easy REF: 10.3 OBJ: 10.3b Identify the diseases caused by diverse Gram-negative bacteria.

MSC: Applying 19. There are multiple causative agents of pneumonia. Which of the following pairs below include two bacterial species known to cause pneumonia? a. Haemophilus influenzae and Moraxella catarrhalis b. Neisseria gonorrhoeae and Vibrio cholera c. Vibrio parahaemolyticus and Bordetella pertussis d. Helicobacter pylori and Francisella tularensis ANS: A DIF: Moderate REF: 10.3 OBJ: 10.3b Identify the diseases caused by diverse Gram-negative bacteria.

MSC: Remembering 20. Which of the following is a characteristic found in all Enterobacteria? a. a cell wall that stains Gram positive b. facultative anaerobic rods c. motility provided by flagella d. obligate aerobes ANS: B DIF: Moderate REF: 10.3 OBJ: 10.3a Describe the diverse environmental roles of Proteobacteria.

MSC: Applying 21. What internal structure is indicated by arrows on this figure?

a. cilia b. flagella

c. mitochondria d. nucleus

ANS: B DIF: Easy REF: 10.4 OBJ: 10.4a Describe the unique coiled cells of the spirochetes.

MSC: Understanding

22. Spirochete cells are unique because they possess a. periplasmic flagella. b. multiple nuclei. c. a thick outer sheath of lipopolysaccharides. d. two distinctive life stages.

ANS: A DIF: Easy REF: 10.4 OBJ: 10.4a Describe the unique coiled cells of the spirochetes.

MSC: Understanding

23. A 23-year-old man visited a community clinic after receiving notification from the health department that a previous sexual partner was diagnosed with a sexually transmitted disease. Although he does not recall having any ulcers, he currently has a macular rash on his trunk, arms, hands, and feet. He is tested for evidence of a. Treponema pallidum pallidum. b. Treponema pallidum pertenue. c. Chlamydia trachomatis. d. Neisseria gonorrhoeae.

ANS: A DIF: Difficult REF: 10.4 OBJ: 10.4b Identify spirochetes that cause important human diseases.

MSC: Evaluating 24. Which of the following causative agents and diseases are correctly paired? a. Borrelia burgdorferi; Lyme disease b. Treponema pallidum; yaws c. Treponema pallidum pertenue; relapsing fever d. Borrelia recurrentis; syphilis ANS: A DIF: Easy REF: 10.4 OBJ: 10.4a Describe the unique coiled cells of the spirochetes.

MSC: Remembering

25. A long, tight, spiral-shaped bacterium is found in the gut of termites. This bacterium is most likely a(n) a. enterobacteria and a pathogen. b. chlamydia and an intracellular parasite. c. spirochete and a symbiont. d. cyanobacteria and a pathogen.

ANS: C DIF: Easy REF: 10.4 OBJ: 10.4c Identify spirochetes that grow as environmental symbionts.

MSC: Applying 26. The specialized shape of a spirochete is advantageous because it a. allows it to rotate and move in a corkscrew motion through viscous environments. b. allows spirochetes to divide more rapidly than cells of other shapes. c. prevents osmotic shock, which is experienced by cocci and rods only. d. provides protection from phagocytosis and antibiotics.

ANS: A DIF: Moderate REF: 10.4 OBJ: 10.4a Describe the unique coiled cells of the spirochetes.

MSC: Applying

27. A black Labrador puppy goes swimming in a nutrient-rich pond one summer afternoon. Within hours the puppy begins vomiting and showing signs of damage to his nervous system. The puppy’s owner takes him to a local veterinarian and is told the puppy also has liver damage. Upon questioning, the owner recalls the pond water the puppy went swimming in was green and cloudy. The veterinarian suspects the puppy was exposed to a. elementary bodies produced by a Chlamydia species. b. toxins produced by a spirochete. c. reticulate bodies produced by a Chlamydia species. d. toxins produced by a cyanobacteria.

ANS: D DIF: Moderate REF: 10.5 OBJ: 10.5a Explain the key environmental contributions of cyanobacteria.

MSC: Evaluating

28. What is the relationship between plants and cyanobacteria? a. Plants produce chlorophylls a and b and pass these pigments on to cyanobacteria. b. Cyanobacteria use oxygen produced by plants and, in return, produce carbon dioxide for use in plants. c. Some cyanobacteria form mutualistic relationships with plants, called lichens. d. Cyanobacteria that were internalized and not broken down by plant cells formed chloroplasts.

ANS: D DIF: Difficult REF: 10.5 OBJ: 10.5a Explain the key environmental contributions of cyanobacteria.

MSC: Applying 29. Cyanobacteria and the bacterial genus Rhizobium are both known to contribute to the environment by a. producing oxygen. b. fixing nitrogen. c. decomposing dead matter. d. producing antibiotics.

ANS: B DIF: Difficult REF: 10.5 OBJ: 10.5a Explain the key environmental contributions of cyanobacteria.

MSC: Understanding 30. Which of the following is true about cyanobacteria? a. They are the only bacteria that produce oxygen. b. They appear red because of their chlorophylls. c. They do very little for the ecosystem. d. They are pathogenic.

ANS: A DIF: Moderate REF: 10.5 OBJ: 10.5a Explain the key environmental contributions of cyanobacteria.

MSC: Remembering 31. The most abundant phototrophs in the ocean are single-celled and include the genera a. Treponema and Chlamydia. b. Synechococcus and Prochlorococcus. c. Merismopedia and Nostoc. d. Oscillatoria and Campylobacter.

ANS: B DIF: Moderate REF: 10.5 OBJ: 10.5b Describe different forms of marine cyanobacteria.

MSC: Remembering

32. Which of the following statements correctly describes a lichen? a. a mutualistic relationship in which spirochetes provide a scaffold for fungal growth b. a mutualistic relationship in which cyanobacteria provide nitrogen to fungi c. a parasitic relationship in which proteobacteria ferment sugars produced by fungi d. a commensal relationship between Firmicutes and fungi that provides no benefits for either organism ANS: B DIF: Moderate REF: 10.5 OBJ: 10.5a Explain the key environmental contributions of cyanobacteria.

MSC: Applying

33. During infertility testing, a young woman is found to have pelvic inflammatory disease, or PID, from persistent inflammation of her fallopian tubes. Although she has never been treated for any sexually transmitted disease, her physician suspects she has an untreated bacterial infection, which is relatively common in the United States. Which bacteria is most likely causing her infection? a. Borrelia burgdorferi c. Borrelia recurrentis b. Chlamydia trachomatis d. Haemophilus influenza ANS: B DIF: Moderate REF: 10.6 OBJ: 10.6b Describe the diseases caused by Chlamydias.

MSC: Analyzing

34. Which of the following statements accurately describes the transmission of one Chlamydia species in human populations? a. Reticulate bodies in secretions from one individual attach to membranes in his or her sexual partner. b. Reticulate bodies remain dormant in the environment for years and attach to host cells when humans come in contact with them. c. Elementary bodies undergo replication within the gut of fleas and infect human cells when fleas bite humans. d. Reticulate bodies replicate inside host cells and develop into elementary bodies that are released when cells lyse.

ANS: D DIF: Difficult REF: 10.6 OBJ: 10.6b Describe the diseases caused by Chlamydias.

MSC: Analyzing

35. Trachoma, an ancient eye disease, is caused by a. Borrelia burgdorferi. c. Moraxella catarrhalis. b. Yersinia pestis. d. Chlamydia trachomatis.

ANS: D DIF: Easy REF: 10.6 OBJ: 10.6b Describe the diseases caused by Chlamydias.

MSC: Remembering

36. A tissue sample from a woman’s reproductive tract reveals human cells that contain growing and dividing reticulate bodies with netlike chromosomes. Which of the following bacterial species has most likely infected the human cells? a. Treponema pallidum c. Chlamydia trachomatis b. Helicobacter pylori d. Coxiella burnetii ANS: C DIF: Moderate REF: 10.6 OBJ: 10.6b Describe the diseases caused by Chlamydias.

MSC: Applying

37. This figure below shows two distinctive life stages associated with a bacteria that

a. b. c. d.

has absent or diminished cell walls. forms filamentous strands in marine environments. causes syphilis. produces oxygen.

ANS: A DIF: Moderate REF: 10.6 OBJ: 10.6b Describe the diseases caused by Chlamydias.

MSC: Understanding

38. The structure highlighted with an arrow in step 6 in the figure below is best described as a

a. nucleus. b. lysosome.

c. vacuole. d. mitochondrion.

ANS: C DIF: Easy REF: 10.6 OBJ: 10.6b Describe the diseases caused by Chlamydias.

MSC: Understanding

39. In which stage of the Chlamydia life cycle, shown in the figure below, is the reproductive element first identified?

a. 1 b. 3

c. 4 d. 6

ANS: B DIF: Moderate REF: 10.6 OBJ: 10.6b Describe the diseases caused by Chlamydias.

MSC: Understanding

40. Which of the following is considered metabolically inactive? a. an elementary body of Chlamydia trachomatis b. a reticulate body of Chlamydophila pneumonia c. a vegetative Bacillus anthracis cell d. a biofilm containing Bacteroides ANS: A DIF: Moderate REF: 10.6 OBJ: 10.6a Describe the cell cycle of Chlamydias.

MSC: Understanding

41. CASE HISTORY Michael, 45 years old, is a cook at a fast-food restaurant in Rome, Georgia. He went to see his physician because he was feeling fatigued, was unable to sleep, had lost his appetite, and had been coughing for several weeks. His sputum (material coughed from deep in the lung) contained acid-fast bacilli, and a chest X-ray revealed scattered, small (1–5 mm) granulomas (nodules of inflammation) throughout both lobes of the lung. The physician diagnosed Michael with secondary tuberculosis.

Secondary tuberculosis is caused by bacteria reactivated from old lesions in which bacteria have persisted in a dormant state. The causative bacterium is Mycobacterium tuberculosis, a facultative intracellular pathogen that infects only humans and is transmitted through respiratory droplets.

Michael was placed in isolation and started on a long-term, four-drug treatment regimen consisting of isoniazid (fatty acid synthesis inhibitor), rifampin (transcription inhibitor), pyrazinamide (fatty acid synthesis inhibitor), and streptomycin (protein synthesis inhibitor). The four-drug therapy continued for two months, followed by four months with isoniazid and rifampin only. Michael responded well to treatment. Luckily, he was not infected with one of the highly dangerous multidrug-resistant strains (MDr-tB).

Mycobacterium tuberculosis is a member of the Actinobacterium, which causes disease in humans, though other members of this group are environmental microorganisms and some produce useful antibiotics. Which other Actinobacterium is a pathogen of humans? a. Corynebacterium diphtheria b. Propionibacterium freudenreichii c. Streptomyces coelicolor

d. Actinomyces israelii ANS: A DIF: Moderate REF: Case History 10.1 OBJ: 10.2b Describe how diverse Actinobacteria have both positive and negative influences on human health.

MSC: Remembering COMPLETION 1. The major group of bacteria that cause sexually transmitted infections and the eye disease trachoma and are obligate intracellular pathogens is ________.

ANS: Chlamydia, Chlamydias, Chlamydiae, Chlamydia DIF: Easy REF: 10.1 OBJ: 10.1a Distinguish among five major groups of bacteria: Gram-positive bacteria, Gram-negative bacteria, spirochetes, Cyanobacteria, and Chlamydias.

MSC: Remembering 2. Structures found in some Gram-positive bacteria that resist desiccation, radiation, freezing, and chemical disinfectants are ________.

ANS: endospores DIF: Easy REF: 10.2 OBJ: 10.2a Describe the traits that enable Firmicutes to survive dryness and persist for long periods.

MSC: Remembering 3. Many Proteobacteria are referred to as ________ because they oxidize minerals for energy.

ANS: lithotrophs DIF: Easy REF: 10.3 OBJ: 10.3a Describe the diverse environmental roles of Proteobacteria.

MSC: Understanding 4. The bacterial cell type shown below is an example of a(n) ________.

ANS: spirochete DIF: Easy REF: 10.4 OBJ: 10.4a Describe the unique coiled cells of the spirochetes.

MSC: Understanding

5. Cyanobacteria are the only bacteria that produce ________.

ANS: oxygen DIF: Easy REF: 10.5 OBJ: 10.5a Explain the key environmental contributions of cyanobacteria.

MSC: Remembering

6. The form of a Chlamydia species outside of a host cell is referred to as a(n) ________ body.

ANS: elementary DIF: Easy REF: 10.6 MSC: Remembering

OBJ: 10.6a Describe the cell cycle of Chlamydias.

SHORT ANSWER 1. Explain how changes in a bacterial genome could cause a nonpathogenic bacterium to develop into a pathogen.

ANS: Changes in a genome can lead to new traits that provide a competitive advantage in a given environment. When the environment used by the bacterium is an organism, such as a human, changes in genes may lead to the bacterium living as a mutualist or pathogen within the organism.

DIF: Moderate REF: 10.1 OBJ: 10.1c Describe how new pathogens emerge to cause new diseases.

MSC: Understanding 2. Autoclaves use high temperatures and steam to sterilize surgical instruments. When instruments are sterilized they do not contain any bacteria. Explain how Bacillus stearothermophilus, a bacterium within the phylum Firmicutes, can be used to test sterilization within autoclaves.

ANS: Endospores produced by the genus Bacillus are highly resistant to destruction by high temperatures. If endospores from Bacillus stearothermophilus are able to germinate and grow after being autoclaved, instruments may not be sterile.

DIF: Difficult REF: 10.2 OBJ: 10.2a Describe the traits that enable Firmicutes to survive dryness and persist for long periods.

MSC: Analyzing 3. The figure of legume roots shown below indicates a relationship between legumes and bacteria.

Describe this relationship and how both partners benefit from the relationship.

ANS: This figure shows an endosymbiotic relationship between a legume and bacteria. The nodules on the legume roots provide an anaerobic environment for bacteria, which also obtain nutrients from the plant. The bacteria fix atmospheric nitrogen, which is often a limiting nutrient for plants.

DIF: Moderate REF: 10.3 OBJ: 10.3a Describe the diverse environmental roles of Proteobacteria.

MSC: Understanding 4. Describe at least one similarity and one difference between the causative agents of syphilis and yaws.

ANS: Syphilis and yaws are both caused by strains of Treponema pallidum, a distinctive spiral-shaped bacterium known as a spirochete. The subspecies that cause these two diseases have slight differences in their genome that most likely cause the differences seen in their infection patterns. Syphilis is sexually transmitted and can infect a fetus. Yaws is transmitted through direct skin contact and cannot infect a fetus.

DIF: Moderate REF: 10.4 OBJ: 10.4b Identify spirochetes that cause important human diseases.

MSC: Applying 5. If all cyanobacteria were suddenly removed from our environment, how would you expect the biosphere to be affected?

ANS: If cyanobacteria were no longer present in our environment, we would expect to see increases in carbon dioxide levels. In addition, nitrogen fixation would decrease and nitrogen in our atmosphere would be less available for other organisms, such as plants. We would also see a decrease in oxygen because cyanobacteria produce oxygen gas that heterotrophs breathe in. The combination of these changes would drastically affect living organisms.

DIF: Moderate REF: 10.5 OBJ: 10.5a Explain the key environmental contributions of cyanobacteria.

MSC: Analyzing 6. Describe the two developmental stages of the Chlamydias.

ANS: Chlamydias possess two developmental stages: elementary bodies and reticulate bodies. Elementary bodies, found outside of host cells, are metabolically inactive and contain condensed chromosomes.

Elementary bodies have a tough outer coat that prevents osmosis. Reticulate bodies, named for the netlike appearance of their chromosomes, are metabolically active and undergo division within host cells. Reticulate bodies lack the tough, protective coat found in elementary bodies.

DIF: Moderate REF: 10.6 MSC: Understanding 7. CASE HISTORY

OBJ: 10.6a Describe the cell cycle of Chlamydias.

Kimiko, a six-year-old girl from Shodo Island, in Japan, had a four-day history of fever, severe abdominal pain, and loose stools. She was diagnosed with appendicitis, but an exploratory laparotomy found a healthy appendix. She responded well to tetracycline antibiotic therapy. The doctors finally concluded she had enteritis (intestinal inflammation). Bacteriological examination of her stool eventually recovered Yersinia pseudotuberculosis, an occasional cause of enteritis. The organism, which is transmitted by ingesting contaminated food or water, was found in the family’s well water and in the stool of animals found on their property.

Is Y. pseudotuberculosis the only member of the Enterobacteriaceae that could have caused Kimiko’s symptoms? If not, describe another organism that also causes enteritis.

ANS: No, Y. pseudotuberculosis is not the only member of the Enterobacteriaceae that could have caused the symptoms. Answers to the second part of the question may vary but should include organisms that are Gram-negative bacilli. This may include Escherichia coli, Salmonella enterica, and so on.

DIF: Easy REF: Case History 10.2 OBJ: 10.3b Identify the diseases caused by diverse Gram-negative bacteria.

MSC: Applying 8. CASE HISTORY Case 1: Diane, a 20-year-old accountant from Cedar City, Utah, came to the Valley View Medical Center urgent-care clinic with a low-grade fever, malaise, and headache. She was sent home with a diagnosis of influenza but again sought treatment seven days later with a macular rash (small, flat, red spots) on her trunk, arms, hands, and feet. Further questioning revealed that one month earlier, Diane had a painless ulcer on her vagina that healed spontaneously. Serology results indicated that Diane had contracted syphilis, caused by Treponema pallidum subspecies pallidum. Because this disease is sexually transmitted, Diane provided a list of her sexual partners over the previous months so the health department could contact them for testing and, if necessary, treatment.

Case 2: Fabrice, an 11-year-old boy from the village of Ngbongbo tokonzi in the Democratic Republic of Congo (Africa), was seen at a nearby clinic. He had a cluster of raised, papular lesions on his arm.

When the doctor asked Fabrice whether he had ever seen lesions like these before, Fabrice remembered having a single lesion about two months earlier, which spontaneously healed. Serology revealed that the boy had secondary yaws disease caused by the spirochete Treponema pallidum subspecies pertenue, which is a spirochete closely related to the strain that causes syphilis. However, T. pallidum pertenue is transmitted by direct contact with a cut or wound.

The organism that caused Fabrice’s illness is closely related to the organism that causes the sexually transmitted disease syphilis. However, transmission routes for the two are completely different. What phenotypic differences are known to exist between the Treponema subspecies, which causes syphilis, and that which causes yaws? Are major changes in genotype (i.e., greater than 1%) required to alter the infection pattern of an organism?

ANS: Only relatively small changes in the genome (0.4%) have been identified, with no morphological distinctions known. However, despite their near identical appearance and similar genomes, the infection patterns and modes of transmission for the two diseases are very distinctive. Children like Fabrice are susceptible to yaws, while syphilis requires sexual contact to move between human hosts.

DIF: Moderate REF: Case History 10.4 | Case History 10.5 OBJ: 10.4b Identify spirochetes that cause important human diseases.

MSC: Analyzing

Chapter 11: Eukaryotic Microbes and Invertebrate Infectious Agents LEARNING OBJECTIVES 11.1a Explain the processes of asexual (vegetative) reproduction and sexual reproduction.

11.1b Distinguish the key traits of fungi, algae, amebas, alveolates, and trypanosomes.

11.1c Distinguish between microbial and invertebrate parasites.

11.2a Describe the structure of the fungal mycelium.

11.2b Explain how fungi impact the environment.

11.2c Describe how different types of fungi cause disease.

11.3a Explain the environmental significance of algae and their relatedness to plants.

11.3b Describe the form and motility of amebas.

11.3c Describe two diseases caused by amebas.

11.4a Describe the distinctive traits of ciliates, dinoflagellates, and apicomplexans.

11.4b Outline the complex life cycle of Plasmodium falciparum and P. vivax, the parasites that cause malaria.

11.5a Describe the traits of trypanosomes.

11.5b Describe the traits of giardias and trichomonads.

11.6a Describe the parasitic cycles of worms, including roundworms, flukes, and tapeworms.

11.6b Describe the parasitic cycles of arthropods, including ticks, mites, and bloodsucking insects.

MULTIPLE CHOICE 1. The cell shown below is best described as a

a. gamete. b. prokaryote.

c. diploid cell. d. haploid cell.

ANS: C DIF: Easy REF: 11.1 OBJ: 11.1a Explain the processes of asexual (vegetative) reproduction and sexual reproduction.

MSC: Applying 2. Which of the following occurs during gamete formation but NOT during asexual reproduction? a. replication of all chromosomes b. paired chromosomes condensing into short rods

c. separation of pairs of homologs d. formation of nuclear membranes around groups of chromosomes ANS: C DIF: Moderate REF: 11.1 OBJ: 11.1a Explain the processes of asexual (vegetative) reproduction and sexual reproduction.

MSC: Applying 3. When comparing sexual reproduction to asexual reproduction, the advantage of sexual reproduction is that it a. generates fewer diverse cell surface proteins and is less likely to activate an immune response. b. requires fewer resources that may be useful when nutrients are depleted. c. produces haploid vegetative cells, which are smaller than diploid vegetative cells. d. increases genetic diversity, which may be useful in a changing environment.

ANS: D DIF: Moderate REF: 11.1 OBJ: 11.1a Explain the processes of asexual (vegetative) reproduction and sexual reproduction.

MSC: Analyzing 4. The group of organisms that includes ciliates, dinoflagellates, and apicomplexans is known as a. fungi. c. trypanosomes. b. amebas. d. alveolates.

ANS: D DIF: Easy REF: 11.1 OBJ: 11.1b Distinguish the key traits of fungi, algae, amebas, alveolates, and trypanosomes.

MSC: Remembering 5. The major group of microbial eukaryotes that contains chloroplasts related to those of plants and is found as a single cell or sheet is termed a. fungi. c. alveolates. b. algae. d. trypanosomes.

ANS: B DIF: Easy REF: 11.1 OBJ: 11.1b Distinguish the key traits of fungi, algae, amebas, alveolates, and trypanosomes.

MSC: Applying 6. The parasite that causes malaria has a complex life cycle involving both a definitive and an intermediate host. This parasitic protist also contains an elaborate cortex. This parasite is best categorized as a(n) a. fungus. c. alveolate. b. trypanosome. d. alga.

ANS: C DIF: Easy REF: 11.1 OBJ: 11.1b Distinguish the key traits of fungi, algae, amebas, alveolates, and trypanosomes.

MSC: Applying 7. Which of the following would be considered invertebrate parasites? a. helminths c. metamonads b. amebas d. algae ANS: A DIF: Moderate REF: 11.1 OBJ: 11.1c Distinguish between microbial and invertebrate parasites.

MSC: Understanding 8. Which of the following would be considered “true” microbes? a. nematodes c. trematodes

b. cestodes

d. fungi

ANS: D DIF: Moderate REF: 11.1 OBJ: 11.1c Distinguish between microbial and invertebrate parasites.

MSC: Understanding 9. When comparing invertebrate parasites to “true” microbes, which of the following is found in invertebrate parasites only? a. fully differentiated organ systems c. macroscopic forms b. cells with mitochondria d. cells with nuclei ANS: A DIF: Moderate REF: 11.1 OBJ: 11.1c Distinguish between microbial and invertebrate parasites.

MSC: Applying 10. The fungal structure shown below is best described as a

a. hyphae pseudopod. b. mycelium.

c. mushroom. d. fruiting body.

ANS: B DIF: Easy REF: 11.2 OBJ: 11.2a Describe the structure of the fungal mycelium.

MSC: Applying

11. One drug target for antifungals is the membrane lipid a. chitin. c. triazole. b. hyphae. d. ergosterol.

ANS: D DIF: Moderate REF: 11.2 OBJ: 11.2a Describe the structure of the fungal mycelium.

MSC: Remembering

12. How do filamentous fungi grow in length? a. Their hyphae undergo mitosis without cell division. b. Their hyphae undergo meiosis to produce new cells. c. They produce asci by mitosis without cell division. d. They produce asci by meiosis without cell division.

ANS: A DIF: Moderate REF: 11.2 OBJ: 11.2a Describe the structure of the fungal mycelium.

MSC: Applying

13. Fungal filaments associated with the root systems of trees that expand the trees’ access to water and nutrients are known as a. mycorrhizae. c. chitin. b. molds. d. saprophytes.

ANS: A

DIF: Easy

REF: 11.2

OBJ: 11.2b Explain how fungi impact the environment.

MSC: Understanding

14. The ability of fungi to digest lignin is important in the a. production of bread. c. decomposition of wood. b. production of beer. d. decomposition of animal bodies.

ANS: C DIF: Easy REF: 11.2 OBJ: 11.2b Explain how fungi impact the environment.

MSC: Understanding

15. Fungi obtain nutrition by a. using chloroplasts for photosynthesis. b. secreting digestive enzymes and absorb broken-down molecules. c. using phagocytosis to transport large molecules across their cell membrane. d. harnessing cyanobacteria to receive carbon and other nutrients.

ANS: B DIF: Easy REF: 11.2 OBJ: 11.2b Explain how fungi impact the environment.

MSC: Applying

16. Why is it frequently more difficult to treat fungal infections in humans than it is to treat bacterial infections? a. The cells found in fungi and humans are more similar than cells of bacteria and humans. b. Humans have not developed medications capable of targeting fungi. c. Fungi normally grow in and on humans, and treating fungal infections would cause death of the human. d. Fungi undergo evolution at a much faster rate than bacteria do.

ANS: A DIF: Difficult REF: 11.2 OBJ: 11.2c Describe how different types of fungi cause disease.

MSC: Evaluating 17. Aspergillus and histoplasmosis infections are both caused by a. opportunistic skin contact with fungi. b. smoking tobacco contaminated with fungal spores. c. swimming in contaminated water. d. inhalation of fungal spores.

ANS: D DIF: Moderate REF: 11.2 OBJ: 11.2c Describe how different types of fungi cause disease.

MSC: Understanding 18. Fungi that form spore-dispersing asci are known as a. basidiomycetes. c. microsporidia. b. zygomycetes. d. ascomycetes.

ANS: D DIF: Moderate REF: 11.2 OBJ: 11.2c Describe how different types of fungi cause disease.

MSC: Understanding 19. Cyanobacteria engulfed by an ancient proto-alga led to the development of ________in both algae and plants. a. mitochondria c. ribosomes b. a nucleus d. chloroplasts ANS: D DIF: Easy REF: 11.3 OBJ: 11.3a Explain the environmental significance of algae and their relatedness to plants.

MSC: Understanding

20. Which of the following mechanisms does an ameba use for locomotion? a. cilia c. flagella b. pseudopods d. amoebas are non-motile ANS: B DIF: Moderate REF: 11.3 OBJ: 11.3b Describe the form and motility of amebas.

MSC: Remembering

21. On an evolutionary timeline, which of the following organisms appeared last? a. cyanobacteria c. algae b. proto-algae d. plants ANS: D DIF: Moderate REF: 11.3 OBJ: 11.3a Explain the environmental significance of algae and their relatedness to plants.

MSC: Analyzing 22. Filamentous amoebas a. form inorganic shells made of calcium carbonate. b. contain large, bulky pseudopods. c. move using cytoplasmic streaming. d. utilize chloroplasts for photosynthesis.

ANS: A DIF: Easy REF: 11.3 OBJ: 11.3b Describe the form and motility of amebas.

MSC: Remembering

23. Amoeba proteus, a lobed ameba, most likely moves by using a. flagella. c. cytoplasmic streaming. b. cilia. d. needlelike pseudopods.

ANS: C DIF: Moderate REF: 11.3 OBJ: 11.3b Describe the form and motility of amebas.

MSC: Understanding

24. The function of the process shown below in the life cycle of Entamoeba histolytica is that it

a. forms a cyst that leaves the host and remains viable in water supplies for weeks. b. forms a trophozoite that leaves the host and remains viable in water supplies for weeks. c. allows an ingested amebic trophozoite to develop into a cyst that can feed on red blood

cells. d. allows an ingested amebic cyst to develop into a trophozoite that can feed on red blood cells.

ANS: D DIF: Moderate REF: 11.3 OBJ: 11.3c Describe two diseases caused by amebas.

MSC: Understanding

25. Blood and fecal samples are collected from a man with dysentery to determine the causative agent and appropriate treatment. Which of the following would most clearly indicate amebic infection? a. immunological tests indicating the presence of Shigella b. a Wheatley’s trichrome stain indicating a protozoa with ingested red blood cells c. a Gram stain indicating the presence of Gram-negative bacteria d. an endospore stain indicating the presence of endospores ANS: B DIF: Moderate REF: 11.3 OBJ: 11.3c Describe two diseases caused by amebas.

MSC: Applying

26. A free-living soil ameba may contaminate contact lens solutions and cause amebic keratitis. What is the genus name of one common causative agent of amebic keratitis? a. Acanthamoeba c. Babesia b. Entamoeba d. Toxoplasma ANS: A DIF: Moderate REF: 11.3 OBJ: 11.3c Describe two diseases caused by amebas.

27. Which of the following is unique to ciliates? a. presence of cilia b. ability to use endocytosis

MSC: Remembering

c. microtubules within cytoplasm d. maintenance of two types of nuclei

ANS: D DIF: Moderate REF: 11.4 OBJ: 11.4a Describe the distinctive traits of ciliates, dinoflagellates, and apicomplexans.

MSC: Applying 28. The image shown below indicates two paramecia of opposite mating types during one stage of conjugation in which haploid micronuclei are exchanged. Which of the following statements accurately describes the two cells after this stage is complete?

a. b. c. d.

Both cells are haploid.

Both cells are diploid.

One cell is haploid and the other is diploid.

Both cells become gametes.

ANS: B DIF: Moderate REF: 11.4 OBJ: 11.4a Describe the distinctive traits of ciliates, dinoflagellates, and apicomplexans.

MSC: Understanding

29. Which of the following would be most likely to stop transmission of Plasmodium falciparum and P. vivax to humans? a. ensuring access to clean drinking water b. providing mosquito netting for beds c. checking for ticks after walking in wooded areas d. eliminating bedbugs from sleeping quarters ANS: B DIF: Moderate REF: 11.4 OBJ: 11.4b Outline the complex life cycle of Plasmodium falciparum and P. vivax, the parasites that cause malaria.

MSC: Applying 30. The function of the apical complex on a merozoite form of Plasmodium falciparum is a. aerobic cellular respiration. b. to allow a merozoite to enter a red blood cell. c. to allow asexual reproduction. d. to provide energy for flagella.

ANS: B DIF: Moderate REF: 11.4 OBJ: 11.4b Outline the complex life cycle of Plasmodium falciparum and P. vivax, the parasites that cause malaria.

MSC: Understanding 31. Trypanosoma brucei, the parasite that causes African sleeping sickness, is carried by a. deer ticks. c. tsetse flies. b. Anopheles mosquitoes. d. bedbugs.

ANS: C DIF: Easy REF: 11.5 OBJ: 11.5a Describe the traits of trypanosomes.

MSC: Remembering

32. In the illustrated life cycle of the trypanosome shown below, which of the following forms is nondividing?

a. slender b. stumpy

c. procyclic d. epimastigote

ANS: B DIF: Easy REF: 11.5 OBJ: 11.5a Describe the traits of trypanosomes.

MSC: Understanding

33. In the illustrated life cycle of the trypanosome shown below, which of the following forms proliferates within the definitive host?

a. slender b. stumpy

c. procyclic d. epimastigote

ANS: A DIF: Moderate REF: 11.5 OBJ: 11.5a Describe the traits of trypanosomes.

MSC: Applying

34. Giardia lamblia and Trichomonas vaginalis are both metamonads. One similarity between the two species is a. the presence of cilia. c. the production of cysts. b. the presence of flagella. d. their ability to cross the placenta.

ANS: B DIF: Easy REF: 11.5 OBJ: 11.5b Describe the traits of giardias and trichomonads.

MSC: Applying

35. Which of the following organisms lacks the ability to do aerobic cellular respiration? a. Giardia lamblia c. Toxoplasma gondii b. Caenorhabditis elegans d. Taenia solium ANS: A DIF: Difficult REF: 11.5 OBJ: 11.5b Describe the traits of giardias and trichomonads.

MSC: Applying

36. Why is perianal itching significant in the life cycle of pinworms? a. When a host scratches the anus, pinworm larvae enter the bloodstream. b. Eggs are trapped under fingernails and transferred to new hosts. c. Scratching allows mature worms to break through the surface of the skin. d. Transmission of pinworms ends when the host scratches the anus.

ANS: B DIF: Difficult REF: 11.6 OBJ: 11.6a Describe the parasitic cycles of worms, including roundworms, flukes, and tapeworms.

MSC: Analyzing 37. On a trip to a region of Asia where snails commonly ingest trematode eggs, Rebecca refuses to eat escargot, cooked snails, offered by her roommate. Instead, Rebecca goes fishing because she feels it would be safer to eat fresh fish. Unfortunately, she undercooks the fish and develops a trematode infection. What is the most likely explanation for her infection? a. Free-swimming larvae released by snails in the water developed into a secondary form within the fish. b. The flesh of the fish she ate contained trematode eggs that developed into larvae within her intestine. c. Her fish dinner was most likely contaminated by fecal matter in the water because

trematode transmission is through a fecal-oral route. d. There were dormant trematodes encysted within the flesh of the fish she ate.

ANS: A DIF: Difficult REF: 11.6 OBJ: 11.6a Describe the parasitic cycles of worms, including roundworms, flukes, and tapeworms.

MSC: Evaluating 38. The organism shown in the figure below is a(n)

a. nematode. b. cestode.

c. trematode. d. arthropod.

ANS: B DIF: Moderate REF: 11.6 OBJ: 11.6a Describe the parasitic cycles of worms, including roundworms, flukes, and tapeworms.

MSC: Applying 39. Mites, ticks, and lice all a. are insects. b. are vectors for serious disease agents. c. are ectoparasites. d. deposit eggs within the skin.

ANS: C DIF: Moderate REF: 11.6 OBJ: 11.6b Describe the parasitic cycles of arthropods, including ticks, mites, and bloodsucking insects.

MSC: Applying 40. The organism shown below is designed for living

a. b. c. d.

within the small intestine. on the outer surface of the body. within red blood cells. on the outer surface of the liver.

ANS: B DIF: Easy REF: 11.6 OBJ: 11.6b Describe the parasitic cycles of arthropods, including ticks, mites, and bloodsucking insects.

MSC: Understanding 41. CASE HISTORY Frank, a 45-year-old man, visited the hospital with respiratory distress and a high fever. Frank had diabetes mellitus and had smoked for 25 years. His white blood cell count was 24,000 and his creactive protein was 24 mg/ml, both signs that his immune system was fighting an infection. His chest X-ray showed an abnormal shadow, and his chest computed tomography (CT scan) showed thickened bronchial walls. He was coughing up black sputum. The physician prescribed an antibiotic, cefotiam hydrochloride, but Frank’s condition worsened. By the tenth day, he was producing 100 ml of sputum a day, and the CT scan of his lung showed multiple lesions (clouded regions). Since antibacterial antibiotics had failed, Frank was tested for fungi. A culture of his sputum and PCR amplification of fungal DNA revealed the fungus Aspergillus fumigatus. Frank was treated with the antifungal agents itraconazole, meropenem trihydrate, and amphotericin b, but he died on the 25th day.

What is the most likely cause of Frank’s deterioration following the use of an antibiotic agent? a. Frank was allergic to the antibiotic used. b. The infection progressed at the same rate regardless of the use of this antibiotic. c. Killing of the fungal cells causing the infection induced a severe immune response. d. Frank acquired a secondary bacterial infection.

ANS: B DIF: Moderate REF: Case History 11.1 OBJ: 11.2c Describe how different types of fungi cause disease.

MSC: Analyzing COMPLETION 1. A single-celled eukaryotic microbe proliferating by mitosis is undergoing ________ reproduction.

ANS: asexual, vegetative DIF: Easy REF: 11.1 OBJ: 11.1a Explain the processes of asexual (vegetative) reproduction and sexual reproduction.

MSC: Remembering 2. Branching tufts of filamentous fungal hyphae form structures known as ________.

ANS: mycelium DIF: Easy REF: 11.2 OBJ: 11.2a Describe the structure of the fungal mycelium.

MSC: Remembering

3. Lung diseases caused by filamentous fungi such as Aspergillus fumigatus occur when ________ are inhaled, germinate, and grow into fuzzy colonies within tissues.

ANS: spores DIF: Easy

REF: 11.2

OBJ: 11.2c Describe how different types of fungi cause disease.

MSC: Remembering 4. Lobed amebas and filamentous amebas are differentiated by the form of their ________.

ANS: pseudopod, pseudopods DIF: Easy REF: 11.3 MSC: Understanding

OBJ: 11.3b Describe the form and motility of amebas.

5. The major group of alveolates that possesses two whiplike flagella and includes species that cause “red tide” is known as ________.

ANS: dinoflagellates, dinoflagellate DIF: Easy REF: 11.4 OBJ: 11.4a Describe the distinctive traits of ciliates, dinoflagellates, and apicomplexans.

MSC: Remembering 6. Obligate parasites with a single flagellum, a complex life cycle, and unique organelles called “kinetoplasts” are known specifically as ________.

ANS: trypanosomes DIF: Moderate REF: 11.5 MSC: Remembering

OBJ: 11.5a Describe the traits of trypanosomes.

7. Giardias and trichomonads are both examples of ________.

ANS: metamonads DIF: Easy REF: 11.5 OBJ: 11.5b Describe the traits of giardias and trichomonads.

MSC: Remembering

8. Arthropods that attach to the surface of a human or other vertebrate are referred to as ________.

ANS: ectoparasites DIF: Easy REF: 11.6 OBJ: 11.6b Describe the parasitic cycles of arthropods, including ticks, mites, and bloodsucking insects.

MSC: Remembering SHORT ANSWER 1. You are looking at a group of unicellular organisms under a microscope and are asked to determine whether the organisms are fungi or algae. Name one visible feature that would allow you to make this determination and explain the significance of that feature in the lifestyle of the organism.

ANS:

Algae are autotrophs and would contain chloroplasts that allow them to conduct photosynthesis. Fungi are heterotrophs that absorb nutrients and lack chloroplasts. Another feature that may be visible microscopically is the presence of flagella, found in some algae. Unicellular fungi, known as yeasts, would lack flagella. Flagella allow organisms to move more easily in the aquatic and marine environments inhabited by many algae.

DIF: Moderate REF: 11.1 OBJ: 11.1b Distinguish the key traits of fungi, algae, amebas, alveolates, and trypanosomes.

MSC: Analyzing 2. What distinguishing characteristic places helminths and arthropods under the category of “eukaryotic microbiology” and outside of the category of “true” microbes?

ANS: Helminths and arthropods are invertebrate animals with complex, fully differentiated organ systems.

Although some of the “true” microbes are also multicellular and have large macroscopic forms, they lack the complex organ systems seen in helminths and arthropods.

DIF: Moderate REF: 11.1 OBJ: 11.1c Distinguish between microbial and invertebrate parasites.

MSC: Analyzing 3. Describe two positive impacts fungi have on our environment.

ANS: Although some fungi are pathogens, many fungi improve our environment. Fungi are able to decompose dead matter, such as wood and animal bodies. Fungi produce antibiotics such as penicillin that improve human health. Some foods used by humans, such as beer, cheese, and bread, are produced in part by fungal activity. Some fungi produce edible mushrooms used by humans.

Mycorrhizal fungal filaments associated with plant roots help to provide nutrients and water to plants.

DIF: Moderate REF: 11.2 MSC: Understanding

OBJ: 11.2b Explain how fungi impact the environment.

4. Describe the shared evolutionary event that led to chloroplasts in both algae and plants.

ANS: Evidence that ancient algae developed into multicellular plants includes the presence of organelles called chloroplasts. Chloroplasts developed when a photosynthetic cyanobacterium was taken into, but not digested by, an ancient proto-alga through a process known as endosymbiosis. The photosynthetic cyanobacterium provided carbon and nutrients to the proto-alga, and the cyanobacterium received protection from the proto-alga. Eventually, the cyanobacterium evolved into chloroplasts currently found in both algae and plants.

DIF: Moderate REF: 11.3 OBJ: 11.3a Explain the environmental significance of algae and their relatedness to plants.

MSC: Understanding 5. Isolda travels from her home in Texas to Mexico to visit extended family. During her trip she becomes ill with amebic dysentery after drinking contaminated water. Contrast the form of ameba cell she most likely ingested with the form of ameba cell found within her intestine.

ANS:

Isolda most likely consumed a dormant cyst found in the contaminated water she drank. After ingestion, cysts develop into trophozoites. Trophozoites are the cell form capable of multiplying and ingesting red blood cells.

DIF: Moderate MSC: Applying

REF: 11.3

OBJ: 11.3c Describe two diseases caused by amebas.

6. Describe how the parasites that cause malaria are able to evade an immune response during an infection.

ANS: Plasmodium falciparum and P. vivax merozoite forms use apical complexes to penetrate and enter red blood cells. After the entire merozoite has entered a red blood cell, there is no sign of the internalized parasite on the red blood cell surface for immune system recognition. The immune system does not “see” the parasite until intracellular progeny are released from red blood cells.

DIF: Moderate REF: 11.4 OBJ: 11.4b Outline the complex life cycle of Plasmodium falciparum and P. vivax, the parasites that cause malaria.

MSC: Analyzing 7. How is the development of a hookworm larva different from the development of a pinworm larva?

ANS: Hookworm larvae develop from eggs within soil. Hookworm larvae feed on soil microbes before penetrating the host skin. Hookworm larvae travel through the bloodstream to the lungs and are coughed up and ingested. Pinworm larvae develop within the small intestine from ingested eggs.

DIF: Moderate REF: 11.6 OBJ: 11.6a Describe the parasitic cycles of worms, including roundworms, flukes, and tapeworms.

MSC: Understanding 8. CASE HISTORY Dotty was the two-year-old daughter of a Texas petroleum executive. The family included four children and three dogs. Dotty played outdoors with the other children and ranch animals. She developed a habit of scratching herself on her bottom. Her nanny tried to discourage the habit but did not check further. Within a month, Dotty’s mother, an attorney for the petroleum firm, noticed that other members of the family had developed a similar habit, which they ascribed to discomfort with the humid summer. One evening when the nanny was out, Dotty’s mother changed her daughter’s diaper and noticed white threadlike worms a few millimeters long. A trip to the pediatrician revealed pinworms as well as pinworm eggs. The eggs were observed on a “tape test,” a piece of tape that was pressed to Dotty’s anus and then placed on a slide for light microscopy. The physician prescribed mebendazole (a microtubule inhibitor) for the entire family, including the nanny and the maid who served dinner. Dotty’s mother asked about the dogs; she was told that dogs do not carry pinworms, although they do carry other worms transmissible to humans. Since the drug mebendazole affects only mature worms, further treatment two weeks later was required to attack the eggs and immature worms that had grown in that time. Ultimately, it took six months of treatments to eliminate the infection from the household.

How could Dotty’s pinworm infection have been transmitted to other members of the family? Give specific examples of potential transmission in a household.

ANS:

It is important for the answer to include transport of the egg from the anus of the infected person to the mouth of the next infected person. Eggs trapped under Dotty’s fingernails would have been ingested by family members. This could occur if family members consumed food touched by Dotty, or, because the eggs survive well in the environment, even by making oral contact with fabrics contaminated by the eggs.

DIF: Moderate REF: Case History 11.3 OBJ: 11.6a Describe the parasitic cycles of worms, including roundworms, flukes, and tapeworms.

MSC: Applying 9. CASE HISTORY Brianna, a 22-year-old college student, had returned recently from spring break at the beach in Acapulco, Mexico. She presented at the college clinic complaining of severe abdominal cramps and fever. She also had nausea and bloody diarrhea with mucus. The nurse practitioner collected stool samples and sent them to the laboratory for analysis. Cultures were negative for bacterial pathogens.

A trichrome stain was performed, revealing amebas of the trophozoite (active feeding) stage. The stained amebas contained ingested red blood cells. The appearance of the amebas was characteristic of Entamoeba histolytica, the cause of amebic dysentery (bloody diarrhea), or intestinal amebiasis.

Brianna was treated with paromomycin (an aminoglycoside that inhibits protein synthesis) for seven days, and her symptoms resolved.

Stained amebas isolated from Brianna’s fecal sample indicated amebas in the trophozoite stage. At what life cycle stage did she likely ingest the parasite? Why are other forms less likely?

ANS: It is likely that the cyst form of the parasite was ingested. Because it is far more environmentally resistant than other life cycle stages, the cyst form allows parasites to travel through the environment and via routes such as drinking water to their next host.

DIF: Easy REF: Case History 11.2 OBJ: 11.3b Describe the form and motility of amebas.

MSC: Understanding

Chapter 12: Viruses LEARNING OBJECTIVES 12.1a Describe diverse forms of the virion, or virus particle.

12.1b Explain the function of the viral envelope and accessory proteins.

12.2a Describe the different classes of viral genomes, and give an example of each.

12.2b Explain why different viruses infect different hosts.

12.2c Describe the nature of viroids and prions.

12.3a Explain how viral genomes enter cells.

12.3b Describe the lytic and lysogenic cycles of bacteriophage infection.

12.3c Explain how viruses are cultured using host cells.

12.4a Describe the genome of papillomavirus.

12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes cancer.

12.5a Describe the structure of the influenza virion.

12.5b Explain how the form of the influenza genome enables rapid evolution of novel strains that cause pandemics.

12.5c Describe the replication cycle of influenza virus.

12.6a Describe the structure of the HIV virion.

12.6b Explain the replicative cycle and epidemiology of HIV. 12.6c Describe the positive roles of retroviruses in human health.

MULTIPLE CHOICE 1. One positive aspect of viruses is their function as a. infectious particles. c. cloning vectors. b. pandemic initiators. d. marine predators.

ANS: C DIF: Easy REF: 12.1 OBJ: 12.1a Describe diverse forms of the virion, or virus particle.

MSC: Remembering 2. Which of the following facts supports the argument that viruses are living? a. Viruses lack metabolism for energy and biosynthesis. b. Viruses are capable of being crystallized. c. Some living pathogenic bacteria contain degenerate genomes and rely significantly on a host. d. Viruses cannot replicate without a host.

ANS: C DIF: Moderate REF: 12.1 OBJ: 12.1a Describe diverse forms of the virion, or virus particle.

MSC: Understanding 3. Which of the following is NOT a possible effect of viral replication in the host cell? a. death of the cell c. debilitation of the cell b. differentiation of the cell d. alteration of the genome of the cell ANS: B

DIF: Moderate

REF: 12.1

OBJ: 12.1a Describe diverse forms of the virion, or virus particle.

MSC: Understanding 4. Which of the following is an example of a virus that causes major economic losses in the agriculture industry? a. tobacco mosaic virus c. HIV b. measles virus d. influenza ANS: A DIF: Easy REF: 12.1 OBJ: 12.1a Describe diverse forms of the virion, or virus particle.

MSC: Remembering 5. West Nile virus is capable of infecting many different organisms (humans, birds, raccoons, and so on).

This information indicates that West Nile virus a. has a narrow host range. b. has a broad host range. c. has a narrow tissue tropism. d. is capable of fecal-oral transmission.

ANS: B DIF: Moderate REF: 12.1 OBJ: 12.1a Describe diverse forms of the virion, or virus particle.

MSC: Applying 6. Which of the following could possibly be an ancestor of the large asymmetrical DNA Vaccinia virus? a. a degenerate single-celled organism c. influenza b. a bacteriophage d. a cow ANS: A DIF: Moderate REF: 12.1 OBJ: 12.1b Explain the function of the viral envelope and accessory proteins.

MSC: Applying 7. An enveloped virus obtains its envelope from a. its genome. b. the cytoplasm.

c. the lysis of the host cell. d. the host cell.

ANS: D DIF: Easy REF: 12.1 OBJ: 12.1b Explain the function of the viral envelope and accessory proteins.

MSC: Applying 8. Which of the following is NOT caused by an aberrant protein? a. Creutzfeldt-Jakob disease c. hepatitis b. scrapie d. kuru ANS: C DIF: Moderate REF: 12.2 OBJ: 12.2c Describe the nature of viroids and prions.

MSC: Applying

9. Prion diseases can be acquired by all of the following methods EXCEPT a. the misfolding of an endogenous protein. b. genetic inheritance. c. transmission by a virus. d. transmission by an infectious protein.

ANS: C DIF: Moderate REF: 12.2 OBJ: 12.2c Describe the nature of viroids and prions.

10. Which of the following is NOT a level of viral evolution?

MSC: Applying

a. within an organelle b. within a host community

c. within a viral species population d. within an individual organism

ANS: A DIF: Moderate REF: 12.2 OBJ: 12.2b Explain why different viruses infect different hosts.

MSC: Understanding 11. Which of the following characteristics of the rabies virus is most important for its classification? a. complex capsid morphology b. single-stranded, negative-sense RNA genome c. presence of an envelope d. narrow host range ANS: B DIF: Moderate REF: 12.2 OBJ: 12.2b Explain why different viruses infect different hosts.

MSC: Applying 12. Examine the figure shown below. Which viral classification group would be most NEGATIVELY affected by antiviral reverse transcriptase inhibitors?

a. Group III b. Group IV

c. Group V d. Group VI

ANS: D DIF: Moderate REF: 12.2 OBJ: 12.2a Describe the different classes of viral genomes, and give an example of each.

MSC: Applying 13. Examine the figure shown below. Which viral classification group(s) must package a viral RNAdependent RNA polymerase?

a. Group V and Group III b. Group IV only

c. Group III only d. Group V and Group IV

ANS: A DIF: Difficult REF: 12.2 OBJ: 12.2a Describe the different classes of viral genomes, and give an example of each.

MSC: Applying 14. Which of the following ensures the presence and expression of host surface proteins capable of being bound to by viruses? a. transduction c. lysogeny b. natural selection d. lysis ANS: B DIF: Moderate REF: 12.3 OBJ: 12.3a Explain how viral genomes enter cells.

MSC: Understanding

15. Gelatin is needed to culture animal viruses in tissue culture because a. animal viruses use gelatin as an energy source. b. cells in tissue culture require gelatin to grow. c. gelatin slows the dispersal of viruses from infected cells, allowing for plaques to form. d. gelatin is used to stain viral plaques.

ANS: C DIF: Easy REF: 12.3 OBJ: 12.3a Explain how viral genomes enter cells.

MSC: Understanding

16. What type of bacteriophage infection results in immediate death of the host cell? a. lysogenic c. latent b. lytic d. chronic ANS: B DIF: Moderate REF: 12.3 OBJ: 12.3b Describe the lytic and lysogenic cycles of bacteriophage infection.

MSC: Understanding 17. If 100% of the DNA contents of a transducing bacteriophage were DNA from the host chromosome, what would happen when the bacteriophage infected a new bacterial cell? a. More bacteriophage would be synthesized, resulting in death of the new bacterial cell. b. No more bacteriophage would be synthesized, as there is no bacteriophage genome available to direct synthesis. c. The new bacterial cell would die.

d. The bacteriophage would be converted from a lysogenic phage to a lytic bacteriophage.

ANS: B DIF: Difficult REF: 12.3 OBJ: 12.3b Describe the lytic and lysogenic cycles of bacteriophage infection.

MSC: Analyzing 18. Examine the figure shown below. What is indicated by the lines?

a. plaques b. bacterial cells

c. latent virus d. animal virus

ANS: A DIF: Moderate REF: 12.3 OBJ: 12.3c Explain how viruses are cultured using host cells.

MSC: Understanding

19. Culturing viruses is difficult because viruses a. require oxygen. b. must be grown inside a living cell. c. require complex nutrients. d. cannot be cultured.

ANS: B DIF: Moderate REF: 12.3 OBJ: 12.3c Explain how viruses are cultured using host cells.

MSC: Understanding

20. How is HPV able to keep its genome so small? a. overlapping reading frames b. oncogenic transformation c. antigenic shift d. HPV does not have a small genome.

ANS: A DIF: Moderate REF: 12.4 OBJ: 12.4a Describe the genome of papillomavirus.

21. Replication of HPV is activated when a. the DNA is uncoated. b. infecting basal cells.

MSC: Remembering

c. integrating into the host genome. d. keratinocytes differentiate.

ANS: D DIF: Moderate REF: 12.4 OBJ: 12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes cancer.MSC: Understanding 22. What type of HPV causes cancer? a. all types of HPV b. no types of HPV

c. some types of latent HPV d. all types of actively replicating HPV

ANS: C DIF: Moderate REF: 12.4 OBJ: 12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes cancer.MSC: Understanding 23. Why must the genome of HPV enter the nucleus for replication? a. HPV uses its own polymerase that cannot function in the cytoplasm. b. The pH of the nucleus allows for replication of HPV RNA. c. The DNA genome of HPV can only be replicated in the nucleus where host DNA polymerase is found. d. The genome of HPV is not replicated in the nucleus.

ANS: C DIF: Difficult REF: 12.4 OBJ: 12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes cancer.MSC: Analyzing 24. HPV virions are assembled a. in the nucleus. b. in the cytoplasm.

c. in the ribosome. d. outside the cell.

ANS: A DIF: Moderate REF: 12.4 OBJ: 12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes cancer.MSC: Understanding 25. A virus might have evolved to cause cancer in a host cell to a. kill the host cell. b. produce more cells for the virus to infect. c. allow for increased mutagenesis of the virus. d. Viruses are not capable of causing cancer in a host cell.

ANS: B DIF: Difficult REF: 12.4 OBJ: 12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes cancer.MSC: Analyzing 26. What type of HPV can be eliminated from the body by the host immune system? a. oncogenic HPV c. all HPV b. nononcogenic HPV d. no HPV ANS: B DIF: Easy REF: 12.4 OBJ: 12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes cancer.MSC: Remembering 27. Segmented influenza RNA genomes are capable of a. reverse transcription. c. reassortment. b. cell fusion. d. proviral transposition.

ANS: C DIF: Easy REF: 12.5 OBJ: 12.5a Describe the structure of the influenza virion.

MSC: Remembering

28. Which of the following statements regarding the influenza virus is FALSE? a. The influenza genome is very tiny to allow the generation of as many virions as possible. b. The influenza genome maximizes gene reassortment. c. The influenza genome is well designed for evasion of the immune system. d. The influenza genome allows for large quantities of virions to be created for continued infection.

ANS: A

DIF: Moderate

REF: 12.5

OBJ: 12.5b Explain how the form of the influenza genome enables rapid evolution of novel strains that cause pandemics.

MSC: Understanding 29. All of the following are possible when considering a new pandemic influenza strain EXCEPT a. the genome of influenza is well designed for evasion of the immune response. b. avian influenza strains can be directly transmitted to other host species, such as humans. c. pigs are considered “melting pots” that can be infected by human and avian strains. d. human influenza RNA segments can reassort with segments from different host species.

ANS: B DIF: Moderate REF: 12.5 OBJ: 12.5b Explain how the form of the influenza genome enables rapid evolution of novel strains that cause pandemics.

MSC: Understanding 30. Which of the following stages of the influenza infection cycle is inhibited by Tamiflu? a. the coating of the capsid envelope b. the assembly of the capsid c. the cleaving of the host receptor and release of the virus by budding d. the packaging of viral genome segments and exit from the nucleus ANS: C DIF: Moderate REF: 12.5 OBJ: 12.5c Describe the replication cycle of influenza virus.

MSC: Applying

31. Influenza must have highly efficient host-to-host transmission because of a. its rapid infection. c. genetic reassortment. b. its slow infection. d. latent infection.

ANS: A DIF: Moderate REF: 12.5 OBJ: 12.5c Describe the replication cycle of influenza virus.

MSC: Applying

32. After budding of new influenza virions, the host cell a. becomes cancerous. c. remains the same. b. becomes transformed. d. is destroyed.

ANS: D DIF: Easy REF: 12.5 OBJ: 12.5c Describe the replication cycle of influenza virus.

MSC: Remembering

33. Which of the following characteristics do HPV and HIV have in common? a. They are both retroviruses. c. They are both DNA viruses. b. They both have overlapping genes. d. The have the same tissue tropism.

ANS: B DIF: Moderate REF: 12.6 OBJ: 12.6a Describe the structure of the HIV virion.

34. What is the cure for infection with HIV? a. vaccine b. radiation

MSC: Applying

c. antiviral drugs d. There is no cure for HIV.

ANS: D DIF: Moderate REF: 12.6 OBJ: 12.6b Explain the replicative cycle and epidemiology of HIV. MSC: Understanding 35. So few HIV virions released in the blood are actually infectious because a. reverse transcriptase has a high error rate. b. HIV is not a very infectious virus. c. the immune system inhibits these virions from causing infections. d. very few cells in the immune system express the receptor HIV requires for binding.

ANS: A DIF: Moderate REF: 12.6 OBJ: 12.6b Explain the replicative cycle and epidemiology of HIV. MSC: Understanding 36. A small subset of the human population does not express the CD4 and CCR5 receptors. To what virus are these individuals naturally immune? a. HIV c. influenza b. HPV d. hepatitis ANS: A DIF: Moderate REF: 12.6 OBJ: 12.6b Explain the replicative cycle and epidemiology of HIV. MSC: Applying 37. A big reason as to why HIV thus far cannot be cured is that it a. is a retrovirus. c. contains integrase. b. contains a viral envelope. d. contains a protease.

ANS: C DIF: Difficult REF: 12.6 OBJ: 12.6b Explain the replicative cycle and epidemiology of HIV. MSC: Analyzing 38. Which of the following viruses is capable of causing a syncytium? a. hepatitis c. HPV b. influenza d. HIV ANS: D DIF: Easy REF: 12.6 OBJ: 12.6b Explain the replicative cycle and epidemiology of HIV. MSC: Understanding 39. CASE HISTORY Sean was a 19-year-old college sophomore, a member of a fraternity at a large Midwestern university.

Sean visited the campus health center, where he told the nurse practitioner that the shaft of his penis had a raised spot. The spot caused no discomfort yet, but Sean knew it was abnormal. The practitioner told Sean that he probably had human papillomavirus (HPV), a cause of genital warts. Although some HPV strains cause warts on external skin, genital HPV is transmitted only by sexual intercourse. The practitioner conducted a physical exam and discovered additional raised spots on Sean’s anus. Sean told the practitioner that he had recently had vaginal sex with women, and had also experimented sexually with other men. The practitioner told Sean that the warts would probably go away on their own if he maintained good sleep and health habits, keeping his immune system strong, but some HPV strains can persist for years without symptoms. The warts could be removed by freezing or chemical treatment, but the virus would persist. Meanwhile, the presence of HPV suggested that Sean was likely to contract related strains causing cancer of the penis or anus. The practitioner recommended use of condoms, although HPV may infect areas that condoms do not protect. She also suggested that Sean recommend the Gardasil HPV vaccine for his younger brother and sister before they become sexually active.

Which of the following is true of papillomavirus infection? a. Genital HPV can be contracted via contact with warts on another person’s skin, for example a wart on the fingers. b. Condoms provide full protection against genital HPV. c. Freezing or otherwise removing genital warts eliminates the infection. d. The HPV vaccine can prevent infection with cancer-causing HPV strains.

ANS: D DIF: Easy REF: Case History 12.1 OBJ: 12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes

cancer.MSC:

Understanding

COMPLETION 1. During viral infection of a host cell, ________ proteins are expressed and are packaged between the envelope and the capsid during envelope formation.

ANS: tegument DIF: Easy REF: 12.1 OBJ: 12.1b Explain the function of the viral envelope and accessory proteins.

MSC: Understanding 2. Herpes viruses have a ________ genome.

ANS: double-stranded DNA DIF: Easy REF: 12.2 OBJ: 12.2a Describe the different classes of viral genomes, and give an example of each.

MSC: Remembering 3. An infectious particle with an RNA genome and no capsid is known as a ________.

ANS: viroid DIF: Easy REF: 12.2 MSC: Remembering

OBJ: 12.2c Describe the nature of viroids and prions.

4. A phage genome integrated into the DNA of the bacterial host cell is known as a ________.

ANS: prophage DIF: Easy REF: 12.3 OBJ: 12.3b Describe the lytic and lysogenic cycles of bacteriophage infection.

MSC: Remembering 5. Human papillomavirus contains a ________ genome.

ANS: double-stranded DNA DIF: Easy REF: 12.4 MSC: Remembering

OBJ: 12.4a Describe the genome of papillomavirus.

6. Influenza contains a ________ genome.

ANS: single-stranded RNA DIF: Easy REF: 12.5 OBJ: 12.5a Describe the structure of the influenza virion.

MSC: Remembering

7. A retrovirus that causes infections progressing slowly over many years is classified as a ________.

ANS: lentivirus

DIF: Easy REF: 12.6 OBJ: 12.6b Explain the replicative cycle and epidemiology of HIV. MSC: Remembering 8. The viral protease found in HIV is essential for ________ of viral proteins in their active forms.

ANS: cleavage DIF: Easy REF: 12.6 OBJ: 12.6b Explain the replicative cycle and epidemiology of HIV. MSC: Remembering 9. Lentiviruses like HIV can be used positively for ________.

ANS: gene therapy DIF: Easy REF: 12.6 OBJ: 12.6c Describe the positive roles of retroviruses in human health.

MSC: Understanding SHORT ANSWER 1. A herpes virus contains an icosahedral capsid that allows for radial symmetry. Explain why this type of capsid formation is beneficial for the virus.

ANS: A capsid that contains radial symmetry can be composed of many repeating protein units. These repeating protein units can come from a small number of genes, as opposed to the large number of genes that would be required by unsymmetrical capsids. Having a small number of genes gives the virus an advantage when replicating its genome, as it can make more viral particles than a virus with a more genes.

DIF: Difficult REF: 12.1 OBJ: 12.1a Describe diverse forms of the virion, or virus particle.

MSC: Analyzing 2. Explain how antigenic drift requires individuals to get a flu vaccine yearly.

ANS: Antigenic drift occurs when a virus mutates so much that its surface proteins have sufficiently changed to the point where they are no longer recognized by host antibodies. Receiving a flu vaccine one year can provide you with the antibodies to recognize one type of flu, but when that virus mutates for the following year, the antibodies taken in the previous year will no longer be helpful against the mutated virus. Therefore, you need to receive another flu vaccine the following year to be protected against that virus.

DIF: Difficult REF: 12.2 OBJ: 12.2b Explain why different viruses infect different hosts.

MSC: Analyzing 3. Why have the majority of viruses evolved to bind to a host surface receptor that serves an essential function in the host cell?

ANS: Host surface receptors that are essential for the host will always be expressed and present on the host—which means a virus that binds to this receptor will always have a way of gaining entry into the cell to replicate.

DIF: Difficult MSC: Analyzing

REF: 12.3

OBJ: 12.3a Explain how viral genomes enter cells.

4. You are attempting to propagate bacteriophage of Bacillus cereus using a liquid batch culture.

A growing culture of B. cereus is inoculated with your bacteriophage. Immediately after inoculation, you take a sample but are unable to detect any bacteriophage. What is happening?

ANS: This is the eclipse period where all bacteriophage are replicating inside bacterial cells and are therefore not detectable in the growth media.

DIF: Moderate REF: 12.3 OBJ: 12.3c Explain how viruses are cultured using host cells.

MSC: Applying

5. Imagine that a new form of gene therapy that can eliminate expression of heparan sulfate proteoglycans has been invented. Explain how this therapy would have both a positive result and a negative result.

ANS: Eliminating the heparan sulfate proteoglycan expression will prevent infection by HPV, as that is the receptor to which it binds. However, it will also inhibit the ability of the skin to heal wounds, as that is the normal function of these proteins.

DIF: Difficult REF: 12.4 OBJ: 12.4b Explain the infectious cycle of papillomavirus, and explain how papillomavirus causes cancer.MSC: Evaluating 6. Differentiate between antigenic drift and antigenic shift. Explain how one can lead to a global pandemic.

ANS: Antigenic drift occurs when envelope proteins of one type of influenza mutate so that the strain is now capable of evading the immune system when it was not before. Antigenic shift occurs when two or more influenza viruses infect the same cell and undergo genetic reassortment, forming a completely new influenza virus. Antigenic shift is more likely to result in a very new and potentially very virulent form of influenza that could lead to a global pandemic.

DIF: Difficult REF: 12.5 OBJ: 12.5b Explain how the form of the influenza genome enables rapid evolution of novel strains that cause pandemics.

MSC: Analyzing 7. Examine the figure shown below. If a chemical that inhibits the fusion of endosomes and lysosomes were added to influenza grown in cell culture, what effect would this have?

ANS: Replication of the influenza virus would be inhibited, as fusion of the endosome and the lysosome are important for the disassembly of the infectious virion.

DIF: Difficult REF: 12.5 OBJ: 12.5c Describe the replication cycle of influenza virus.

MSC: Analyzing

8. Explain why the HIV virion structure contains a tRNA from the host.

ANS: The tRNA from a previously infected host cell complexes with the RNA genome to serve as a primer so that reverse transcriptase can convert the RNA to DNA. DIF: Difficult MSC: Analyzing

REF: 12.6

OBJ: 12.6a Describe the structure of the HIV virion.

9. Infection with lentiviruses such as HIV can be lethal; however, lentiviruses may potentially be used to save lives. What features of these viruses allow them to be used for gene therapy, and can they be used to fight disease? Be specific and include an example of a disease for which this approach could be employed.

ANS: Integration sequences are maintained and virulence genes are removed and replaced with a corrected version of a defective human gene. An HIV-derived vector has been used to cure a child of leukemia, and the genetic neurodegenerative disease ALD is also mentioned in the text as an example; however, many genetic diseases would be theoretically acceptable.

DIF: Difficult REF: 12.6 OBJ: 12.6c Describe the positive roles of retroviruses in human health.

MSC: Applying 10. CASE HISTORY Eighteen-year-old Aisha was a first-year student at a small private college in New England. In the fall of 2009, the campus implemented management procedures for the expected H1N1 influenza pandemic.

Students with flu symptoms were told to “self-isolate” and to report their status on a college webform.

By the end of October, there were 50 students reporting per week.

One night, Aisha felt hot, flushed, and unsteady on her feet. Her thermometer showed a temperature of 39C (102F). She started coughing, and she felt extremely tired. She managed to find the webform on her computer, although her arm was shaking and made false starts. Finally, she typed her information and confirmed her status report. A college security officer arrived at her room wearing a face mask. The officer gave Aisha a face mask and told her to collect her essential personal items and books; Aisha did the best she could in her fevered state. The officer drove her to a separate residence reserved for suspected H1N1 cases. There Aisha lay in the bed and tried to sleep. In the morning a nurse’s aide brought a tray of food and medication including oral oseltamivir (Tamiflu) and inhaled zanamivir (relenza). The tray was left on the floor in the hallway, outside Aisha’s isolation room. Aisha had to drag herself out of bed to open the door and get the tray. She was required to stay in the isolation room until two days after her temperature returned to normal. She and most other infected students made a full recovery, although one student was hospitalized with life-threatening complications.

The college security officer who interacted with Aisha when she contracted H1N1 influenza had received a flu shot earlier in the season, before this strain was included in the vaccine. He had also previously been infected with influenza as a child. Why did this officer exercise such precaution (e.g., wearing a face mask) in interacting with Aisha? How is the influenza virus able to infect a person with previous immunity?

ANS: Influenza is capable of producing novel antigens unrecognizable to the immune systems of people previously vaccinated or infected. The two primary mechanisms for this are antigenic drift and the more significant change produced by reassortment or antigenic shift.

DIF: Moderate REF: Case History 12.2 OBJ: 12.5b Explain how the form of the influenza genome enables rapid evolution of novel strains that cause pandemics.

MSC: Applying 11. CASE HISTORY

Ralph, 24 years old, had just been promoted at the car dealership where he worked in sales. He was ready to propose to his girlfriend, a bank clerk. It had been several years since Ralph had engaged in risky behaviors, but he and his girlfriend both decided to get tested for STDs. That is how Ralph learned that he was HIV positive. The diagnosis came as a surprise, since Ralph had no symptoms of disease. His T-cell count, however, had dipped to 500 cells/mm3 (normal level is about 1,200 cells/mm3). Now he faced the dilemma of how to avoid infecting his future wife and how to conceive healthy children.

The doctor informed Ralph of his treatment options. The current recommendation of the Centers for Disease Control and Prevention (CDC) is to commence antiretroviral therapy as soon as an individual tests positive for the virus. A single daily pill was prescribed, containing tenofovir and emtricitabine (reverse transcriptase inhibitors, together marketed as Truvada). The advantage of early treatment with Truvada is the early halt in decline of T cells and the decrease in transmission risk.

Some physicians, however, recommend starting antivirals only when T-cell counts fall below 500 cells/mm3, to delay the deleterious side effects of the drugs and to postpone selection for drugresistant strains. Ralph was also told of options for conceiving children without infection, such as the “sperm washing” procedure that eliminates HIV from sperm for artificial insemination. He had a lot to discuss with his girlfriend.

Truvada is an antiviral medication prescribed to treat HIV. List and describe the two components of the drug and how they target the virus.

ANS: Tenofovir and emtricitabine are both reverse transcription inhibitors. HIV is an RNA virus. Upon entry of the virus into the host cell, it must convert its RNA to DNA. It accomplishes this via the viral enzyme reverse transcriptase. These two drugs target the viral enzyme and prevent the virus from converting RNA to DNA, therefore blocking its ability to integrate into the host chromosome.

DIF: Difficult REF: Case History 12.3 OBJ: 12.6c Describe the positive roles of retroviruses in human health.

MSC: Applying

Chapter 13: Sterilization, Disinfection, and Antibiotic Therapy LEARNING OBJECTIVES 13.1a Distinguish between sterilization, disinfection, antisepsis, and sanitation.

13.1b Differentiate bacteriostatic agents from bactericidal agents.

13.1c Discuss decimal reduction time and its use in sterilizing material.

13.2a Compare autoclave sterilization with pasteurization.

13.2b Explain the difference between refrigeration and lyophilization.

13.2c Describe the uses of filtration and laminar flow biological safety cabinets.

13.2d List conditions in which irradiation can be used to sterilize.

13.3a List factors that can affect the efficacy of a disinfectant.

13.3b Explain how disinfectants are compared.

13.3c List the basic forms of commercial disinfectants.

13.3d Describe the emergence of microbial resistance to disinfectants.

13.4a Explain the concept of selective toxicity and its importance for clinically useful antibiotics.

13.4b Explain what is meant by spectrum of activity, and discuss its clinical importance.

13.4c Discuss how the effectiveness of an antibiotic is tested, and differentiate minimal inhibitory concentration (MIC) from minimal bacteriostatic concentration (MBC).

13.4d Describe the chemotherapeutic index.

13.5a Classify antibiotics by their molecular targets.

13.5b Describe the process of cell wall synthesis, and indicate the targets for various cell wall antibiotics.

13.5c Distinguish transcription inhibitors from translation inhibitors.

13.6a Describe the four basic mechanisms of antibiotic resistance.

13.6b Explain how drug resistance develops.

13.6c Outline strategies to counteract drug resistance.

13.7a List the basic targets of antiviral inhibitors.

13.7b Discuss selective toxicity for antiviral drugs.

13.7c Explain the spectrum of activity for antiviral drugs.

13.8a Describe the major targets of antifungal agents.

13.8b Discuss selective toxicity for antifungal agents.

MULTIPLE CHOICE 1. In which of the following mechanisms of microbial control might some pathogens still survive? a. sanitization c. disinfection b. antisepsis d. sterilization ANS: A DIF: Moderate REF: 13.1 OBJ: 13.1a Distinguish between sterilization, disinfection, antisepsis, and sanitation.

MSC: Understanding 2. Which of the following organisms is NOT killed by a germicidal agent? a. bacteria c. fungi b. viruses d. endospores

ANS: D DIF: Easy REF: 13.1 OBJ: 13.1b Differentiate bacteriostatic agents from bactericidal agents.

MSC: Remembering 3. Hannibal Lecter, an infamous serial killer, is attempting to use H2O2 to remove the bloodstains of his latest victim from his 100% cashmere scarf and for disinfection purposes. Why is it taking him so long to disinfect his scarf? a. H2O2 is not a good disinfection agent. b. This type of disinfection procedure is best completed at colder temperatures. c. Blood is an example of organic load that can inhibit the process of disinfection. d. The organisms on his scarf are resistant to H2O2.

ANS: C DIF: Moderate REF: 13.1 OBJ: 13.1c Discuss decimal reduction time and its use in sterilizing material.

MSC: Applying 4. Which of the following terms can describe the death rate of microbial cells when exposed to an antibacterial agent? a. linear c. reverse logarithmic b. exponential d. polar ANS: B DIF: Moderate REF: 13.1 OBJ: 13.1c Discuss decimal reduction time and its use in sterilizing material.

MSC: Understanding 5. Standard conditions for sterilization by ________ are 121C and 15 psi for 20 minutes. a. autoclaving c. tyndallization b. pasteurization d. lyophilization ANS: A DIF: Easy REF: 13.2 OBJ: 13.2a Compare autoclave sterilization with pasteurization.

MSC: Understanding 6. 12D is the amount of time required to a. kill 1012 spores. b. kill 1012 cells.

c. reduce the population by 1012. d. kill 90% of the population.

ANS: A DIF: Easy REF: 13.2 OBJ: 13.2a Compare autoclave sterilization with pasteurization.

MSC: Understanding 7. Glycerol is used to protect cells during a. refrigeration. b. deep-freezing.

c. lyophilization. d. filtration.

ANS: B DIF: Moderate REF: 13.2 OBJ: 13.2b Explain the difference between refrigeration and lyophilization.

MSC: Applying 8. Which of the following is NOT a purpose of low temperatures in microbiology? a. inhibit microbial growth c. kill microorganisms b. stop microbial metabolism d. preserve microorganisms ANS: C DIF: Moderate REF: 13.2 OBJ: 13.2b Explain the difference between refrigeration and lyophilization.

MSC: Understanding

9. Because it is an essential component for every individual, supplements may be required if enough vitamin C is not found in the diet. Vitamin C is sensitive to heat. So that it can be safe for human consumption, how can vitamin C be sterilized before being packaged into supplements? a. autoclave c. filtration b. pasteurization d. lyophilization ANS: C DIF: Moderate REF: 13.2 OBJ: 13.2c Describe the uses of filtration and laminar flow biological safety cabinets.

MSC: Applying 10. Which of the following does NOT affect the sensitivity of a microorganism to food irradiation? a. genome size c. whether the food is fresh or frozen b. rate of repair of DNA damage d. the presence of heat-shock enzymes ANS: D DIF: Moderate REF: 13.2 OBJ: 13.2d List conditions in which irradiation can be used to sterilize.

MSC: Applying 11. Which of the following is NOT a factor affecting the efficacy of a disinfectant? a. the barometric pressure b. the presence of blood c. the presence of endospore-forming bacteria d. the corrosiveness of the disinfectant ANS: A DIF: Moderate REF: 13.3 OBJ: 13.3a List factors that can affect the efficacy of a disinfectant.

MSC: Applying 12. Examine the table below. Which disinfectant is the most effective against Salmonella typhi based on the phenol coefficient?

a. chloramine b. mercury chloride

c. formalin d. hydrogen peroxide

ANS: B DIF: Moderate REF: 13.3 OBJ: 13.3b Explain how disinfectants are compared.

MSC: Analyzing

13. Chemicals that are ________ with the structure R-CHO are very useful disinfectants. a. iodophors c. anionic detergents b. low-molecular-weight aldehydes d. cationic detergents ANS: B DIF: Moderate REF: 13.3 OBJ: 13.3c List the basic forms of commercial disinfectants.

MSC: Applying

14. Which of the following disinfectants has a high CDC level of activity? a. hydrogen peroxide c. phenol b. quarternary ammonium compounds d. chlorine gas ANS: A DIF: Moderate REF: 13.3 OBJ: 13.3c List the basic forms of commercial disinfectants.

MSC: Understanding

15. Which of the following is NOT a characteristic of a biofilm that makes it resistant to disinfectants? a. presence of an extracellular matrix b. stress-induced physiology of surface cells c. stress-induced physiology of cells deep in the biofilm d. metabolic collaboration between multiple species ANS: B DIF: Moderate REF: 13.3 OBJ: 13.3d Describe the emergence of microbial resistance to disinfectants.

MSC: Understanding 16. Drug sensitivity occurs when a(n) a. drug is broken down by a pathogenic organism. b. organism is inhibited by a drug. c. individual develops an allergic reaction to a drug he or she is taking. d. drug that is used to inhibit the growth of an organism is no longer capable.

ANS: C DIF: Easy REF: 13.4 OBJ: 13.4a Explain the concept of selective toxicity and its importance for clinically useful antibiotics.

MSC: Remembering 17. The term antibiotic is usually reserved for drugs that target a. viruses. c. fungi. b. bacteria. d. protozoa.

ANS: B DIF: Easy REF: 13.4 OBJ: 13.4b Explain what is meant by spectrum of activity, and discuss its clinical importance.

MSC: Remembering 18. Which of the following statements regarding the minimum inhibitory concentration (MIC) is FALSE? a. The MIC is the same for one drug regardless of bacterial species. b. The MIC is the lowest concentration of a drug that will prevent the growth of an organism. c. The MIC can be affected by how well a drug penetrates a cell. d. The MIC can be affected by the affinity of the drug for the intracellular target.

ANS: A DIF: Moderate REF: 13.4 OBJ: 13.4c Discuss how the effectiveness of an antibiotic is tested, and differentiate minimal inhibitory concentration (MIC) from minimal bacteriostatic concentration (MBC).

MSC: Understanding 19. Which of the following is NOT a standard parameter of the Kirby-Bauer test? a. the size of the agar plate b. the depth of the medium

c. moderate composition d. the method of spreading organisms onto the plate ANS: D DIF: Moderate REF: 13.4 OBJ: 13.4c Discuss how the effectiveness of an antibiotic is tested, and differentiate minimal inhibitory concentration (MIC) from minimal bacteriostatic concentration (MBC).

MSC: Understanding 20. Drug A has a toxic dose of 17 g/kg of body weight and a therapeutic dose of 8 g/kg of body weight.

Drug B has a toxic dose of 6 g/kg of body weight and a therapeutic dose of 4 g/kg of body weight.

Which of the following statements is true? a. Drug B is the safer drug. c. Drug B has a higher therapeutic index. b. Drug A is the safer drug. d. Drug A has a lower therapeutic index.

ANS: B DIF: Moderate REF: 13.4 OBJ: 13.4d Describe the chemotherapeutic index.

MSC: Applying

21. The cotreatment of septic Enterococcus infections with vancomycin and an aminoglycoside is an example of antibiotic a. synergism. c. sensitivity. b. antagonism. d. resistance.

ANS: A DIF: Easy REF: 13.4 OBJ: 13.4d Describe the chemotherapeutic index.

MSC: Understanding

22. The function of polymyxin is similar to that of a detergent. What cell structure will be most affected by this drug? a. cell membrane c. ribosome b. cell wall d. chromosome ANS: A DIF: Moderate REF: 13.5 OBJ: 13.5a Classify antibiotics by their molecular targets.

MSC: Understanding

23. Which antibiotic inhibits the formation of the peptide side chain of NAM? a. vancomycin c. bacitracin b. cycloserine d. cephalexin ANS: B DIF: Moderate REF: 13.5 OBJ: 13.5b Describe the process of cell wall synthesis, and indicate the targets for various cell wall antibiotics.

MSC: Remembering 24. Which of the following will result from inhibited topoisomerases? a. no cell wall synthesis c. impaired DNA synthesis b. deficient plasma membrane d. impaired RNA synthesis ANS: C DIF: Moderate REF: 13.5 OBJ: 13.5c Distinguish transcription inhibitors from translation inhibitors.

MSC: Understanding 25. Which antibiotic resistance mechanism is exemplified by beta-lactamase? a. destroy the antibiotic before it gets into the cell b. modify the target so that it no longer binds the antibiotic c. add modifying groups that inactivate the antibiotic d. pump the antibiotic out of the cell ANS: A

DIF: Moderate

REF: 13.6

OBJ: 13.6a Describe the four basic mechanisms of antibiotic resistance.

MSC: Applying 26. Administering antibiotics before knowing the cause of the infection is specifically known as a. chemotherapy. c. prophylactic therapy. b. empirical therapy. d. persistence therapy.

ANS: B DIF: Easy REF: 13.6 OBJ: 13.6b Explain how drug resistance develops.

MSC: Remembering

27. Which of the following actions of an individual will NOT inhibit the need for antibiotics? a. frequent handwashing b. aromatherapy c. avoiding the use of antibiotics for viral infections d. vaccinations ANS: B DIF: Easy REF: 13.6 OBJ: 13.6c Outline strategies to counteract drug resistance.

MSC: Remembering

28. Inhibition of viral envelope acidification would ________ an influenza infection. a. inhibit c. have no effect on b. enhance d. speed up ANS: A DIF: Moderate REF: 13.7 OBJ: 13.7a List the basic targets of antiviral inhibitors.

MSC: Applying

29. How do DNA analogs act to inhibit replication of an RNA virus? a. DNA analogs do not inhibit RNA viruses. b. by inhibiting RNA polymerase c. by inhibiting DNA polymerase d. by preventing protein synthesis ANS: A DIF: Moderate REF: 13.7 OBJ: 13.7a List the basic targets of antiviral inhibitors.

MSC: Understanding

30. Protease inhibitors are common antiviral drugs targeting a. HPV. c. hepatitis C. b. HIV. d. influenza.

ANS: B DIF: Easy REF: 13.7 OBJ: 13.7a List the basic targets of antiviral inhibitors.

MSC: Remembering

31. Highly active antiretroviral therapy is used to treat a. HPV. c. hepatitis C. b. HIV. d. influenza.

ANS: B DIF: Easy REF: 13.7 OBJ: 13.7a List the basic targets of antiviral inhibitors.

MSC: Remembering

32. Viruses cause more illnesses on an everyday basis than do bacteria. Why are there so few antiviral agents compared to antibacterial agents? a. Viruses are a bigger problem in developing countries where they do not have the funds to develop antiviral drugs. b. Since viruses are not living, there are no drugs that can stop their proliferation. c. Viruses use functions of the host to replicate themselves, so achieving selective toxicity is difficult.

d. Viruses do not cause as many deadly diseases and therefore have not been targeted with antivirals.

ANS: C DIF: Easy REF: 13.7 OBJ: 13.7b Discuss selective toxicity for antiviral drugs.

MSC: Understanding

33. Which of the following is NOT a category of antifungal agents? a. polyenes c. allylamines b. azoles d. cephalosporins ANS: D DIF: Easy REF: 13.8 OBJ: 13.8a Describe the major targets of antifungal agents.

MSC: Understanding

34. Griseofulvin demonstrates selective toxicity by a. inhibiting DNA synthesis of fungal DNA only. b. disrupting the mitotic spindle of fungi but not humans. c. blocking synthesis of a fungal cell wall. d. inhibiting synthesis of fungal-specific ergosterol.

ANS: B DIF: Easy REF: 13.8 OBJ: 13.8a Describe the major targets of antifungal agents.

MSC: Understanding

35. All of the following are molecules that can be selectively targeted by antibiotics EXCEPT a. peptidoglycan. c. DNA. b. 30S ribosomal subunit. d. 50S ribosomal subunit.

ANS: B DIF: Easy REF: 13.8 OBJ: 13.5a Classify antibiotics by their molecular targets.

MSC: Understanding

36. Fungal cells grown in the presence of fluconazole have a. impaired cell division. c. defective cell walls. b. mutations in DNA. d. defective cell membranes.

ANS: D DIF: Moderate REF: 13.8 OBJ: 13.8a Describe the major targets of antifungal agents.

MSC: Remembering

37. What is the major downside to the often necessary long-term treatment with fungal drugs? a. dry skin c. antifungal resistance b. high cost d. potential toxic side effects ANS: D DIF: Moderate REF: 13.8 OBJ: 13.8b Discuss selective toxicity for antifungal agents.

MSC: Understanding

38. CASE HISTORY Three-year-old Molly was brought to the emergency department crying. She had a stiff neck and high fever (40 C, or 104 F). Gram stain of her cerebrospinal fluid revealed Gram-positive cocci, generally in pairs. The attending physician diagnosed Molly with meningitis and immediately prescribed intravenous ampicillin. Unfortunately, the child’s condition worsened, so antibiotic treatment was changed to a third-generation cephalosporin (ceftriaxone). Molly began to improve within hours and was released after two days. A report from the clinical microbiology laboratory two days later identified the organism as Streptococcus pneumoniae. The report also included antibiotic susceptibility results, which revealed that this strain of S. pneumoniae was resistant to ampicillin but remained susceptible to cephalosporin.

The first antibiotic used to treat Molly, ampicillin, has activity against both Gram-negative and Grampositive bacteria; however, the bacterium that made Molly ill was resistant to this agent. At the time the antibiotic was prescribed, neither the type of agent nor its resistances were known. Based on this information, which of the following is true? a. Ampicillin is a broad-spectrum antibiotic. b. Gram-positive bacteria are resistant to ampicillin, so it should be used only for Gramnegative infections. c. Molly’s illness should have been treated with a narrow-spectrum antibiotic. d. Molly’s infection is resistant to a broad variety of antibiotics.

ANS: A DIF: Moderate REF: Case History 13.1 OBJ: 13.4b Explain what is meant by spectrum of activity, and discuss its clinical importance.

MSC: Analyzing 39. CASE HISTORY Three-year-old Molly was brought to the emergency department crying. She had a stiff neck and high fever (40 C, or 104 F). Gram stain of her cerebrospinal fluid revealed Gram-positive cocci, generally in pairs. The attending physician diagnosed Molly with meningitis and immediately prescribed intravenous ampicillin. Unfortunately, the child’s condition worsened, so antibiotic treatment was changed to a third-generation cephalosporin (ceftriaxone). Molly began to improve within hours and was released after two days. A report from the clinical microbiology laboratory two days later identified the organism as Streptococcus pneumoniae. The report also included antibiotic susceptibility results, which revealed that this strain of S. pneumoniae was resistant to ampicillin but remained susceptible to cephalosporin.

The clinical laboratory performed a Kirby-Bauer assay to determine the antibiotic susceptibility of S. pneumoniae. Which of the following is true about this assay? a. It uses serial dilutions to determine the MIC. b. It is performed on an agar plate and the antibiotic diffuses throughout the media. c. It is performed on a mannitol salt agar plate. d. It can tell you which antibiotic is bactericidal.

ANS: B DIF: Moderate REF: Case History 13.1 OBJ: 13.4b Explain what is meant by spectrum of activity, and discuss its clinical importance.

MSC: Analyzing 40. CASE HISTORY Three-year-old Molly was brought to the emergency department crying. She had a stiff neck and high fever (40 C, or 104 F). Gram stain of her cerebrospinal fluid revealed Gram-positive cocci, generally in pairs. The attending physician diagnosed Molly with meningitis and immediately prescribed intravenous ampicillin. Unfortunately, the child’s condition worsened, so antibiotic treatment was changed to a third-generation cephalosporin (ceftriaxone). Molly began to improve within hours and was released after two days. A report from the clinical microbiology laboratory two days later identified the organism as Streptococcus pneumoniae. The report also included antibiotic susceptibility results, which revealed that this strain of S. pneumoniae was resistant to ampicillin but remained susceptible to cephalosporin.

The drug cephalosporin was selected to treat Molly’s infection. Cephalosporin is classified as a narrow-spectrum drug because it a. specifically targets the peptidoglycan present in the cell wall of Gram-positive organisms. b. targets the bacterial ribosome and inhibits protein synthesis. c. interferes with enzymes necessary for bacterial replication. d. targets DNA gyrase and blocks transcription.

ANS: A

DIF: Moderate

REF: Case History 13.1

OBJ: 13.4b Explain what is meant by spectrum of activity, and discuss its clinical importance.

MSC: Analyzing COMPLETION 1. The process by which all living cells, spores, and viruses are destroyed on an object is called ________.

ANS: sterilization DIF: Easy REF: 13.1 OBJ: 13.1a Distinguish between sterilization, disinfection, antisepsis, and sanitation.

MSC: Remembering 2. The process of heating foods to a moderately high temperature long enough to kill most heat-resistant, non-spore-forming pathogens is known as ________.

ANS: pasteurization DIF: Easy REF: 13.2 OBJ: 13.2a Compare autoclave sterilization with pasteurization.

MSC: Remembering 3. The removal of 99.9% of airborne particulate matter larger than 0.3m in size can be accomplished with a(n) ________.

ANS: safety cabinet DIF: Moderate REF: 13.2 OBJ: 13.2c Describe the uses of filtration and laminar flow biological safety cabinets.

MSC: Understanding 4. The presence of ________, such as blood, can require longer exposure times to a chemical in order to achieve true disinfection.

ANS: organic matter DIF: Moderate REF: 13.3 OBJ: 13.3a List factors that can affect the efficacy of a disinfectant.

MSC: Applying 5. Wescodyne and betadine are examples of ________ complexed with organic carriers.

ANS: iodine DIF: Moderate REF: 13.3 OBJ: 13.3c List the basic forms of commercial disinfectants.

MSC: Understanding

6. The presence of ________ in the bacterial cell wall is one of the mechanisms of antibiotic selective toxicity.

ANS: peptidoglycan

DIF: Easy REF: 13.4 OBJ: 13.4a Explain the concept of selective toxicity and its importance for clinically useful antibiotics.

MSC: Understanding 7. A drug is classified as bactericidal if its minimum bactericidal concentration is no more than ________ its minimum inhibitory concentration.

ANS: four times; 4X DIF: Moderate REF: 13.4 OBJ: 13.4c Discuss how the effectiveness of an antibiotic is tested, and differentiate minimal inhibitory concentration (MIC) from minimal bacteriostatic concentration (MBC).

MSC: Understanding 8. Penicillin targets peptidoglycan synthesis to inhibit ________.

ANS: cell wall formation; formation of the cell wall DIF: Easy REF: 13.5 OBJ: 13.5a Classify antibiotics by their molecular targets.

MSC: Understanding

9. Aminoglycosides inhibit translation by binding to the ________.

ANS: 30S ribosomal subunit DIF: Moderate REF: 13.5 OBJ: 13.5c Distinguish transcription inhibitors from translation inhibitors.

MSC: Understanding 10. Some bacteria “play dead” when an antibiotic is present, only to grow again when the antibiotic is gone. This action is called ________.

ANS: persistence DIF: Easy REF: 13.6 MSC: Remembering

OBJ: 13.6b Explain how drug resistance develops.

11. Neuraminidase inhibitors that target viral release can be used to treat infections with ________.

ANS: influenza DIF: Moderate REF: 13.7 MSC: Remembering

OBJ: 13.7a List the basic targets of antiviral inhibitors.

12. A category of antifungal agents that inhibit DNA synthesis is known as ________.

ANS: flucytosine DIF: Moderate REF: 13.8 OBJ: 13.8a Describe the major targets of antifungal agents.

SHORT ANSWER

MSC: Remembering

1. Explain how a bacteriostatic antibiotic is useful even if it does not result in the death of the pathogen.

ANS: A bacteriostatic antibiotic will slow the growth of the pathogen enough for the immune system of the infected individual to take action and eliminate the pathogen from the body. Thus, the antibiotic is useful even though it does not directly kill the pathogen.

DIF: Difficult REF: 13.1 OBJ: 13.1b Differentiate bacteriostatic agents from bactericidal agents.

MSC: Analyzing 2. Examine the image below. Determine the decimal reduction time and describe what this means.

ANS: The decimal reduction time is approximately one minute. This means that 90% of the population is killed in one minute.

DIF: Difficult REF: 13.1 OBJ: 13.1c Discuss decimal reduction time and its use in sterilizing material.

MSC: Applying 3. Why does lyophilization offer longer-term storage of mesophilic cells than refrigeration?

ANS: While mesophilic cells that are refrigerated will have their growth substantially slowed, they will still be viable, metabolizing cells sensitive to the conditions of the media around them. Eventually these conditions will dry out and deteriorate enough to result in death of the cells. Lyophilization freezedries cultures, removing all water from media and cells, leaving cells in a powder form and not actively metabolic, protecting them from the conditions of the media around them.

DIF: Moderate REF: 13.2 OBJ: 13.2b Explain the difference between refrigeration and lyophilization.

MSC: Applying 4. Explain why norovirus and the prion that causes bovine spongiform encephalopathy are not susceptible to irradiation of food.

ANS: Viruses have fewer nucleotides than bacteria and eukaryotic organisms, making them less susceptible to radiation that targets nucleic acids to kill organisms. Prions are not composed of nucleic acids at all, so they are not susceptible to normal levels of radiation used in microbial control of food preparation.

DIF: Moderate REF: 13.2 OBJ: 13.2d List conditions in which irradiation can be used to sterilize.

MSC: Applying 5. The presence (+) or absence (−) of growth of a specific organism after exposure to the shown dilutions of phenol and disinfectant A for 5, 10, or 15 minutes is shown in the table below. Calculate the phenol coefficient for this disinfectant.

ANS: The phenol coefficient is 200/70, or approximately 2.9.

DIF: Difficult MSC: Applying

REF: 13.3

OBJ: 13.3b Explain how disinfectants are compared.

6. Explain how organisms can develop resistance to chemical disinfectants.

ANS: Disinfectants that have multiple targets at high concentration often have only a single target inside the cell that they are capable of inhibiting at low concentrations. Therefore, it is possible for organisms to become resistant to the disinfectant at low concentrations. Answers could also include specific mechanisms organisms use for resistance, such as drug efflux pumps.

DIF: Moderate REF: 13.3 OBJ: 13.3d Describe the emergence of microbial resistance to disinfectants.

MSC: Applying 7. Give an example of when you would want to use a broad-spectrum antibiotic and when you would want to use a narrow-spectrum antibiotic. Give a disadvantage to using a broad-spectrum antibiotic.

ANS: A broad-spectrum antibiotic should be used when you do not specifically know the causative agent. A disadvantage to using it is that it will eliminate more organisms than just the causative agent, resulting in a greater disruption to the natural flora of the host and potentially leading to the spread of antibiotic resistance. A narrow-spectrum antibiotic should be used when you know exactly what the causative agent is and you have an antibiotic that will target just that organism or only a small number of organisms that include the causative agent.

DIF: Difficult REF: 13.4 OBJ: 13.4b Explain what is meant by spectrum of activity, and discuss its clinical importance.

MSC: Analyzing 8. Explain what the therapeutic index is. If two antibiotics can be used to treat an infection and they are equal except for their therapeutic indexes, should the doctor prescribe the drug with a high therapeutic index or the drug with a low therapeutic index?

ANS: Therapeutic index is the ratio of the toxic dose, the maximum dose tolerated by the patient before death, to the therapeutic dose, the minimum dose that stops pathogen growth. Ideally, a high quantity of the antibiotic will be tolerated before becoming toxic and a low quantity of the antibiotic will be required to stop pathogen growth. Therefore, a higher therapeutic index is better, and the doctor should prescribe the drug with a higher therapeutic index.

DIF: Moderate MSC: Evaluating

REF: 13.4

OBJ: 13.4d Describe the chemotherapeutic index.

9. Explain why penicillin is toxic for susceptible bacteria that are actively growing but has no effect on dormant bacteria.

ANS: Penicillin targets cell wall synthesis. Bacteria that are actively growing and dividing are constantly synthesizing more cell wall components. Therefore, penicillin inhibits this process and results in death of the cell. Dormant bacteria are not synthesizing a cell wall and are therefore not affected by penicillin.

DIF: Moderate REF: 13.5 OBJ: 13.5b Describe the process of cell wall synthesis, and indicate the targets for various cell wall antibiotics.

MSC: Analyzing 10. Describe how the antibiotic resistance mechanism using drug efflux pumps works. How could the medical community respond to this resistance mechanism to overcome it?

ANS: Some organisms resist antibiotics by using drug efflux pumps, single component or multicomponent, to pump antibiotics out of the cell. There are a variety of acceptable answers for ways in which the medical community could respond to this resistance mechanism. One of them is to administer efflux pump inhibitors along with antibiotics to prevent these pumps from functioning.

DIF: Difficult REF: 13.6 OBJ: 13.6a Describe the four basic mechanisms of antibiotic resistance.

MSC: Evaluating 11. Describe how avoiding the use of antibiotics for viral infections can prevent the spread of antibiotic resistance.

ANS: Taking antibiotics unnecessarily for a viral infection exposes the bacteria in your body to antibiotics, increasing the chance that resistance to the antibiotic will develop. Additionally, all bacteria sensitive will be killed while the resistant bacteria will survive and continue to grow, leading to a higher ratio of resistant bacteria relative to sensitive bacteria.

DIF: Moderate REF: 13.6 OBJ: 13.6c Outline strategies to counteract drug resistance.

MSC: Analyzing

12. Explain how DNA chain-terminating analog antivirals are selectively toxic despite the fact that the viruses they target and the host cell both contain DNA genomes.

ANS: Viral polymerases more readily incorporate these analogs than do host cell polymerases that are more selective. Therefore the viruses are more susceptible to these analogs than are host cells.

DIF: Moderate MSC: Applying

REF: 13.7

OBJ: 13.7b Discuss selective toxicity for antiviral drugs.

13. Explain why antifungal agents are less selectively toxic than antibacterial agents.

ANS: Fungi are eukaryotic organisms just like humans are, and they share many of the same cell structures and biochemical pathways with human cells. Therefore, it is more difficult to selectively target cell components unique to fungi.

DIF: Moderate REF: 13.8 OBJ: 13.8b Discuss selective toxicity for antifungal agents.

MSC: Analyzing

14. CASE HISTORY Titus, a nine-month-old infant, suffered from a series of chronic problems after birth, including respiratory syncytial virus bronchiolitis (infection and inflammation of the bronchioles) and neonatal group B Streptococcal sepsis. (Neonatal sepsis happens soon after birth and is often caused by lancefield group B Streptococcus agalactiae, passed to the newborn from an infected mother.) As a result of his weakened state, Titus was fitted with a gastrostomy feeding tube so that his parents could feed him. Within a week of being sent home, however, Titus was rushed to the Johns Hopkins Hospital with an acute onset of fever, cough, regurgitation from his gastrostomy feeding tube, and dehydration.

Physical exam confirmed that the boy had a severe cough resulting in respiratory distress, a rapid heart rate, and moderate dehydration. A nasopharyngeal aspirate (the nasopharynx is the nasal part of the pharynx) was positive for influenza A antigen. Titus was diagnosed with influenza and treated with the antiviral drug oseltamivir. He gradually improved and was discharged four days after admission.

What is the mechanism of action for the drug, oseltamivir, used to treat Titus’s influenza infection?

Why would antibiotics such as 50S ribosomal inhibitors have had no effect on this viral infection?

ANS: Oseltamivir is a neuraminidase inhibitor that prevents the release of influenza virions from infected cells. Only influenza has an appropriate target for this drug, limiting its toxicity to patient cells.

Viruses utilize host cell machinery to replicate, including host ribosomes. Thus, agents that would interfere with viral protein production would not be selectively toxic but toxic to host cells as well.

DIF: Moderate

REF: Case History 13.5

OBJ: 13.7b Discuss selective toxicity for antiviral drugs.

MSC: Understanding

15. CASE HISTORY Brian, a 14-year-old boy with fever (39 C, or 102.2 F), chills, and left-sided pleuritic chest pain (pain when inhaling) was referred to a hospital emergency department by his general practitioner. A chest X-ray showed left lower lobe pneumonia. The boy reported that he was allergic to amoxicillin and cephalosporins (as a child he had developed a rash to these agents) and had been taking daily doxycycline (tetracycline) for the previous three months to treat mild acne. He was admitted to the hospital and treated with intravenous erythromycin because of his reported beta-lactam allergies, but he continued to feel sick. The day after admission, both sputum and blood cultures grew Streptococcus pneumoniae. After 48 hours, antibiotic susceptibility results indicated that the microbe was resistant to penicillin, erythromycin, and tetracycline. Armed with this information, the clinician immediately changed antibiotic treatment to vancomycin, a drug still effective in the face of these resistance mechanisms. The boy’s fever resolved over the next 12 hours, and he made a slow but full recovery over the next week.

Would you have predicted the resistance profile of the Streptococcus pneumoniae causing Brian’s infection? Why? ANS: The Streptococcus causing Brian’s infection would have a high likelihood of resistance to tetracycline because of his previous long-term use of the antibiotic. At the point of culture, resistance to erythromycin was predictable because of the lack of efficacy when this antimicrobial was used in treatment. Other resistances would not be predictable from the information given in the case history.

DIF: Moderate REF: Case History 13.4 OBJ: 13.6b Explain how drug resistance develops.

MSC: Analyzing

Chapter 14: Normal Human Microbiota: A Delicate Balance of Power LEARNING OBJECTIVES 14.1a List body compartments that are sterile and discuss why they are sterile.

14.1b List body compartments that are populated by microbiota, and name the key species found in each.

14.1c Identify key features of populated body sites that influence microbiota composition.

14.2a Describe ways that microbiota benefit the health of their host.

14.2b Explain the risks of having a microbiome, especially to immunocompromised hosts.

14.2c Discuss how host-microbiota relationships are studied in the laboratory.

14.2d Describe how the compositional balance of our microbiome can be compromised and the potential effects on the individual.

14.3a List and compare the various barriers that separate the microbiome from its host.

14.3b Explain the function of tight junctions in preventing infection.

14.3c Discuss the role of innate immunity in preventing infection by microbiota.

14.4a Describe mechanisms by which our microbiota communicate with our cells and tissues.

14.4b Explain ways that our cells and tissues communicate with our microbiota.

14.4c Provide examples of the benefits resulting from microbiota-host interactions.

14.4d Argue the case for declaring our microbiome an “organ system” essential to our survival as a species.

14.5a Explain the role of probiotics in maintaining a beneficial microbiome.

14.5b Describe the potential benefits of microbiome transplants, such as fecal transplants, intreating certain diseases.

14.5c Discuss the prospects of phage therapy to control infectious diseases.

14.5d Explain the disappearing microbiota hypothesis.

MULTIPLE CHOICE 1. The presence of ________ is essential for preventing respiratory infections. a. bacteremia c. vegetations b. epidermis d. the mucociliary escalator ANS: D DIF: Easy REF: 14.1 OBJ: 14.1a List body compartments that are sterile and discuss why they are sterile.

MSC: Remembering 2. Which microbial reservoir has the largest anaerobe-to-aerobe ratio? a. intestine c. mouth b. genitourinary tract d. skin ANS: A DIF: Easy REF: 14.1 OBJ: 14.1b List body compartments that are populated by microbiota, and name the key species found in each.

MSC: Understanding 3. When do anaerobes begin to colonize the human oral cavity? a. when teeth emerge c. during birth b. in the womb d. during the first feeding ANS: A DIF: Moderate REF: 14.1 OBJ: 14.1b List body compartments that are populated by microbiota, and name the key species

found in each.

MSC: Understanding

4. Which of the following is NOT a useful function of the gut microflora? a. fermenting unused energy substrates b. training the immune system c. supporting the growth of pathogenic bacteria d. regulating the development of the gut ANS: C DIF: Easy REF: 14.1 OBJ: 14.1b List body compartments that are populated by microbiota, and name the key species found in each.

MSC: Understanding 5. In addition to digested food, where do carbohydrates come from in the large intestine? a. mucus secretions c. saccharolytic fungi b. dead cells d. arteries ANS: A DIF: Moderate REF: 14.1 OBJ: 14.1b List body compartments that are populated by microbiota, and name the key species found in each.

MSC: Understanding 6. What is an optimal pH for the growth of Helicobacter pylori, a common inhabitant of the human stomach? a. pH 1 c. pH 5 b. pH 3 d. pH 7 ANS: C DIF: Moderate REF: 14.1 OBJ: 14.1c Identify key features of populated body sites that influence microbiota composition.

MSC: Applying 7. Individuals take probiotics to a. directly kill intestinal pathogens. b. secrete hormones that lead to weight loss. c. provide a more fermentative environment. d. restore balance to the microbial community.

ANS: D DIF: Moderate REF: 14.1 OBJ: 14.1c Identify key features of populated body sites that influence microbiota composition.

MSC: Applying 8. What would be the expected aerobe to anaerobe ratio of the belly button? a. 10:1 c. 1:100 b. 1:10 d. 1:1000 ANS: B DIF: Moderate REF: 14.1 OBJ: 14.1c Identify key features of populated body sites that influence microbiota composition.

MSC: Analyzing 9. Why do the residents of our normal microbiota not regularly invade other tissues of the body? a. They are inhibited by pathogens. b. They have not evolved the ability. c. They are not able to survive in other tissues. d. Our normal microbiota does regularly invade other tissues of the body.

ANS: B DIF: Moderate REF: 14.2 OBJ: 14.2a Describe ways that microbiota benefit the health of their host.

MSC: Applying

10. Which of the following can act as an immunomodulin? a. cytokines c. catalase b. enterotoxins d. hydrogen peroxide ANS: C DIF: Easy REF: 14.2 OBJ: 14.2a Describe ways that microbiota benefit the health of their host.

MSC: Understanding 11. Which of the following would NOT be a good organism choice for a vaccine delivery system? a. Streptococcus salivarius c. Staphylococcus epidermidis b. Lactobacillus acidophilus d. Staphylococcus aureus ANS: D DIF: Moderate REF: 14.2 OBJ: 14.2a Describe ways that microbiota benefit the health of their host.

MSC: Applying 12. Which of the following is evidenced by the health of gnotobiotic mice? a. Antibiotic resistance is an ever-growing threat. b. The presence of normal microbiota challenges the immune system. c. Epithelial barriers prevent the spread of opportunistic infections. d. Nothing has been learned from gnotobiotic mice.

ANS: B DIF: Moderate REF: 14.2 OBJ: 14.2a Describe ways that microbiota benefit the health of their host.

MSC: Understanding 13. Which of the following situations does NOT demonstrate the importance of a healthy microbiome? a. Mary suffers from colon cancer. While being treated, she develops an opportunistic Bacteroides fragilis infection. b. Andy is lactose intolerant. His body does not break down lactose, so the microorganisms in the gut do it for him. c. Jenna is prone to yeast infections, so she routinely eats yogurt and takes a probiotic supplement to increase the amount of lactic acid bacteria in her vagina. d. Anthony suffers from debilitating diarrhea after a lengthy course of antibiotics to treat his MRSA infection.

ANS: A DIF: Difficult REF: 14.2 OBJ: 14.2b Explain the risks of having a microbiome, especially to immunocompromised hosts.

MSC: Analyzing 14. Which of the following is/are used to study host-microbiota relationships in the laboratory? a. tight junctions c. gnotobiotic animals b. metagenomics d. quorum sensing ANS: C DIF: Easy REF: 14.2 OBJ: 14.2c Discuss how host-microbiota relationships are studied in the laboratory.

MSC: Understanding 15. Which of the following can completely change the intestinal mix of microbes? a. rashes c. antibiotic treatments b. sun exposure d. gnotobiotic delivery ANS: C DIF: Easy REF: 14.2 OBJ: 14.2d Describe how the compositional balance of our microbiome can be compromised and the potential effects on the individual.

MSC: Remembering

16. A noninfectious disease that can be linked to changes in the microbiota is a. yeast infection. c. irritable bowel syndrome. b. C. difficile infection. d. stomach flu.

ANS: C DIF: Easy REF: 14.2 OBJ: 14.2d Describe how the compositional balance of our microbiome can be compromised and the potential effects on the individual.

MSC: Understanding 17. Which of the following is NOT an accurate description for epithelial cells? a. interconnected c. held together by tight junctions b. symmetrical d. glycoprotein-covered ANS: B DIF: Moderate REF: 14.3 OBJ: 14.3a List and compare the various barriers that separate the microbiome from its host.

MSC: Understanding 18. Which of the following is consistently sampling normal bacteria of the host to maintain a low-level immune response? a. a tight junction c. an epithelial cell b. Lymphoid tissue d. an endothelial cell ANS: B DIF: Moderate REF: 14.3 OBJ: 14.3a List and compare the various barriers that separate the microbiome from its host.

MSC: Understanding 19. Which of the following is capable of passing through the placental membrane and endothelial cells to infect the developing fetus? a. Influenza virus c. Staphylococcus aureus b. Listeria monocytogenes d. Hepatitis B ANS: B DIF: Moderate REF: 14.3 OBJ: 14.3a List and compare the various barriers that separate the microbiome from its host.

MSC: Remembering 20. The blood–brain barrier is composed of a. arteries. b. glycoproteins.

c. tight junctions. d. very tight junctions.

ANS: D DIF: Easy REF: 14.3 OBJ: 14.3b Explain the function of tight junctions in preventing infection.

MSC: Remembering 21. What is problematic about treating bacterial infections that have spread to the brain? a. There is potential to harm the good bacteria of the brain. b. Neurons in the brain will degrade antibiotics. c. Many antibiotics are not capable of penetrating the blood–brain barrier. d. Bacterial infections do not spread to the brain.

ANS: C DIF: Moderate REF: 14.3 OBJ: 14.3b Explain the function of tight junctions in preventing infection.

MSC: Applying 22. Endothelial cells are known for using ________ to carry cell components from one side of the cell to the other. a. protein secretion c. cytokine production

b. active vesicle transport

d. ATP synthesis

ANS: B DIF: Moderate REF: 14.3 OBJ: 14.3b Explain the function of tight junctions in preventing infection.

MSC: Understanding 23. Lipopolysaccharides, flagellin, and double-stranded DNA are microbe-associated molecular patterns recognized by a. tight junctions. c. tumor necrosis factors. b. ribosomes. d. pattern recognition receptors.

ANS: D DIF: Moderate REF: 14.3 OBJ: 14.3c Discuss the role of innate immunity in preventing infection by microbiota.

MSC: Applying 24. Examine the figure below. Which Toll-like receptor is activated specifically by Gram-positive organisms?

a. TLR 4 b. TLR 3

c. TLR 2 d. TLR 1

ANS: C DIF: Moderate REF: 14.3 OBJ: 14.3c Discuss the role of innate immunity in preventing infection by microbiota.

MSC: Analyzing 25. Examine the figure below. Which Toll-like receptor is activated specifically by viruses?

a. TLR 9

c. TLR 4

b. TLR 5

d. TLR 3

ANS: D DIF: Easy REF: 14.1 OBJ: 14.1b List body compartments that are populated by microbiota, and name the key species found in each.

MSC: Remembering 26. Where are microbial metabolic end-products found in the body? a. in the blood c. everywhere b. in the urine d. nowhere ANS: C DIF: Moderate REF: 14.4 OBJ: 14.4a Describe mechanisms by which our microbiota communicate with our cells and tissues.

MSC: Understanding 27. Many of the genes affected by colonization with Eubacteria rectale and Bacteroides thetaiotamicron are involved with a. the blood–brain barrier. c. colonic turnover. b. energy production. d. pro-inflammation.

ANS: C DIF: Moderate REF: 14.4 OBJ: 14.4a Describe mechanisms by which our microbiota communicate with our cells and tissues.

MSC: Analyzing 28. The preferred carbon source for epithelial cells is a. glucose. c. norepinephrine. b. L-DOPA. d. butyrate.

ANS: D DIF: Easy REF: 14.4 OBJ: 14.4b Explain ways that our cells and tissues communicate with our microbiota.

MSC: Remembering 29. What can be concluded based on the figures below?

a. b. c. d.

Norepinephrine stimulates biofilm formation of Staphylococcus epidermidis.

Norepinephrine is inhibited by Staphylococcus epidermidis.

Staphylococcus epidermidis is able to use norepinephrine as a carbon source.

Norepinephrine has no effect on Staphylococcus epidermidis.

ANS: A DIF: Difficult REF: 14.4 OBJ: 14.4b Explain ways that our cells and tissues communicate with our microbiota.

MSC: Remembering 30. Which of the following statements regarding quorum sensing is true?

a. b. c. d.

Gene expression is altered when the population of a specific microorganism is low.

Gene expression is altered when the population of a specific microorganism is high.

There is no relationship between quorum sensing and gene expression.

Quorum sensing is a phenomenon very few organisms are capable of accomplishing.

ANS: B DIF: Moderate REF: 14.4 OBJ: 14.4c Provide examples of the benefits resulting from microbiota-host interactions.

MSC: Understanding 31. Which of the following pathologies can develop when the gut microbiome organ is deficient? a. pneumonia c. inflammatory bowel disease b. yeast infection d. ulcers ANS: C DIF: Moderate REF: 14.4 OBJ: 14.4c Provide examples of the benefits resulting from microbiota-host interactions.

MSC: Applying 32. Which of the following is NOT an argument for the consideration of the microbiome as a separate organ system? a. There are ten times more microbial cells than human cells in the body. b. Microbiomes are contained in defined and relatively independent parts of the body. c. Defects in microbiome composition can have dire effects on human health. d. A human microbiome is inherited from the mother and father.

ANS: D DIF: Moderate REF: 14.4 OBJ: 14.4d Argue the case for declaring our microbiome an “organ system” essential to our survival as a species.

MSC: Understanding 33. How do naturally occurring Staphylococcus strains inhibit the growth of pathogenic strains? a. producing antibiotics c. outcompeting for nutrients b. producing short-chain fatty acids d. They do not inhibit pathogenic strains.

ANS: B DIF: Moderate REF: 14.5 OBJ: 14.5a Explain the role of probiotics in maintaining a beneficial microbiome.

MSC: Understanding 34. Which of the following forms of treatment do(es) NOT evolve as pathogens evolve? a. phage therapy c. probiotics b. fecal transplant d. antibiotics ANS: D DIF: Moderate REF: 14.5 OBJ: 14.5c Discuss the prospects of phage therapy to control infectious diseases.

MSC: Analyzing 35. Which of the following is NOT a current or possible future fecal transplant method? a. colonoscopy c. blood infusion b. endoscopy d. capsule ingestion ANS: C DIF: Easy REF: 14.5 OBJ: 14.5b Describe the potential benefits of microbiome transplants, such as fecal transplants, in treating certain diseases.

MSC: Applying 36. Which was developed first? a. fecal transplants b. probiotics

c. antibiotics d. phage therapy

ANS: D DIF: Moderate REF: 14.5 OBJ: 14.5c Discuss the prospects of phage therapy to control infectious diseases.

MSC: Applying 37. Use of preterm antibiotics during labor and delivery has led to a. reduced fecal transmission of bacteria. b. an altered immunological environment. c. reduced vaginal transmission. d. accelerated change of skin microbiome.

ANS: C DIF: Moderate REF: 14.5 OBJ: 14.5d Explain the disappearing microbiota hypothesis.

MSC: Understanding

38. How has the development of clean water NEGATIVELY affected modern civilization? a. reduced fecal transmission of bacteria resulting in missing microbiota b. altered immunological environment c. increased transmission of hormone-activating compounds d. decreased amounts of important trace minerals ANS: A DIF: Moderate REF: 14.5 OBJ: 14.5d Explain the disappearing microbiota hypothesis.

MSC: Applying

39. Which of the following changes in human behavior has NOT altered the composition of the microbiota? a. decreased antibiotic usage c. living in smaller families b. increased cesarean deliveries d. use of antibacterial soaps ANS: A DIF: Easy REF: 14.5 OBJ: 14.5d Explain the disappearing microbiota hypothesis.

MSC: Remembering

40. Which of the following once colonized 80% of individuals in the United States and now only colonizes 10%? a. Helicobacter pylori c. Salmonella typhimurium b. Staphylococcus aureus d. Lactobacillus acidophilus ANS: A DIF: Easy REF: 14.5 OBJ: 14.5d Explain the disappearing microbiota hypothesis.

MSC: Understanding

41. CASE HISTORY Renita, a 67-year-old woman, complained to her physician of having persistent diarrhea with weight loss, bloating, and excess flatulence (passing gas). Renita also said her stools looked greasy, which the physician knew as a sign that ingested fat was not being absorbed. A blood test revealed that the woman’s vitamin B12 level was abnormally low. Cultures of fecal specimens failed to find any typical bacterial pathogens that could cause diarrhea. However, the decreased vitamin B12 level and excess fat in the stool suggested that the woman had a malabsorption disease. The physician, initially perplexed, suddenly realized that the cause could be small intestine bacterial overgrowth disease, a diagnosis confirmed by aspirating fluid from the jejunum (small intestine). The laboratory discovered abnormally high numbers of facultative and anaerobic bacteria in the fluid, including Streptococcus, Escherichia coli, Lactobacillus, and Bacteroides. Fermentation by these organisms produced the bloating and flatulence. Antibiotic treatment corrected the syndrome.

Which best describes the relationship between Renita and her microbiome in this case study? a. Pathogens were present in Renita’s jejunum in addition to normal microbiota. b. Previous antibiotic use disrupted Renita’s normal flora, allowing overgrowth of resistant species.

c. Renita’s immune system was unable to reduce the growth of bacteria in her GI tract, leading to overgrowth of all the bacteria in her microbiome. d. A physiological change such as reduction of bile production allowed microbiota from one portion of Renita’s GI tract to thrive in another, inappropriate area.

ANS: D DIF: Moderate REF: Case History 14.1 OBJ: 14.2d Describe how the compositional balance of our microbiome can be compromised and the potential effects on the individual.

MSC: Evaluating COMPLETION 1. Sequestered body sites tend to be ________.

ANS: sterile DIF: Easy REF: 14.1 OBJ: 14.1a List body compartments that are sterile and discuss why they are sterile.

MSC: Understanding 2. Colonization of the stomach requires the ability to withstand ________ conditions.

ANS: acidic DIF: Moderate REF: 14.1 OBJ: 14.1c Identify key features of populated body sites that influence microbiota composition.

MSC: Understanding 3. Organisms that cause disease in an immunocompromised host only are called ________.

ANS: opportunistic pathogens DIF: Easy REF: 14.2 OBJ: 14.2b Explain the risks of having a microbiome, especially to immunocompromised hosts.

MSC: Understanding 4. The presence of a core set of genes is most important for a healthy ________.

ANS: microbiome DIF: Moderate REF: 14.2 OBJ: 14.2d Describe how the compositional balance of our microbiome can be compromised and the potential effects on the individual.

MSC: Understanding 5. The blood–brain barrier is composed of ________ between the endothelial cells of capillaries feeding the brain.

ANS: tight junctions; very tight junctions DIF: Easy REF: 14.3 OBJ: 14.3a List and compare the various barriers that separate the microbiome from its host.

MSC: Understanding 6. The presence of Eubacteria recale and Beta thetaiotamicron affect ________ of the host.

ANS: gene expression DIF: Easy REF: 14.4 OBJ: 14.4a Describe mechanisms by which our microbiota communicate with our cells and tissues.

MSC: Remembering 7. Production of indole by E. coli tells host intestinal epithelial cells to tighten tight junctions and increase production of ________.

ANS: anti-inflammatory products DIF: Moderate REF: 14.4 OBJ: 14.4c Provide examples of the benefits resulting from microbiota-host interactions.

MSC: Understanding 8. Probiotics have been used in baby chicks to prevent colonization by ________.

ANS: Salmonella DIF: Easy REF: 14.5 OBJ: 14.5a Explain the role of probiotics in maintaining a beneficial microbiome.

MSC: Remembering 9. Fecal transplants can be used to treat ulcerative colitis caused by ________.

ANS: Clostridium difficile DIF: Easy REF: 14.5 OBJ: 14.5b Describe the potential benefits of microbiome transplants, such as fecal transplants, in treating certain diseases.

MSC: Remembering SHORT ANSWER 1. Explain how a nonpathogenic organism like Staphylococcus epidermidis present in the lungs of an individual with cystic fibrosis can still cause problems.

ANS: While S. epidermidis does not cause a disease, if it is allowed to colonize the lungs of a compromised individual, it could form a biofilm that can damage lungs and interfere with lung function.

DIF: Moderate REF: 14.1 OBJ: 14.1b List body compartments that are populated by microbiota, and name the key species found in each.

MSC: Applying 2. Describe the positive and negative sides of enterotoxins.

ANS: The negative side of enterotoxins is the diarrhea and damage to the intestines. The positive side of enterotoxins is the activation of calcium channels in intestinal epithelial cells to protect against colorectal cancer.

DIF: Moderate

REF: 14.2

OBJ: 14.2a Describe ways that microbiota benefit the health of their host.

MSC: Applying 3. What is wrong with the situation described below?

After vaginal delivery, a gnotobiotic mouse was moved to an axenic environment.

ANS: Gnotobiotic mice must be delivered via C-section, otherwise they will be exposed to the bacteria present in the vaginal canal and will not be germ-free.

DIF: Difficult REF: 14.2 OBJ: 14.2c Discuss how host-microbiota relationships are studied in the laboratory.

MSC: Analyzing 4. Label the figure shown below.

ANS: The labels should be as shown:

DIF: Moderate REF: 14.3 OBJ: 14.3b Explain the function of tight junctions in preventing infection.

MSC: Analyzing 5. A nonmotile Gram-negative organism has breached a tight junction barrier. How will this organism be detected and what will happen immediately inside the host to protect it from infection?

ANS: The lipopolysaccharide and microbial DNA will be detected by Toll-like receptors 4 and 9, respectively, on cells of the innate immune system. This will result in these cells sending a signal to the nucleus to begin production of cytokines and immunoregulatory proteins that stimulate the immune system.

DIF: Difficult REF: 14.3 OBJ: 14.3c Discuss the role of innate immunity in preventing infection by microbiota.

MSC: Applying 6. Give an example of how our cells communicate with the microbiome.

ANS: A variety of answers are possible, including behavioral and physical factors as well as hormones affecting composition.

DIF: Moderate REF: 14.4 OBJ: 14.4b Explain ways that our cells and tissues communicate with our microbiota.

MSC: Applying 7. Give three reasons for why the microbiome should be considered an independent organ system.

ANS: The microbiome is contained in defined areas, is independent, and performs specific functions depending on its location inside the body. Its defects also result in pathology.

DIF: Moderate REF: 14.4 OBJ: 14.4d Argue the case for declaring our microbiome an “organ system” essential to our survival as a species.

MSC: Applying 8. Explain two potential negative effects of using phage therapy to treat bacterial infections.

ANS: A variety of answers are possible. Some include the following: The human immune system could produce a large immune response against the phage (much like what can happen with some individuals using antibiotics). The phage could also target nonpathogenic good bacteria. Unlike drugs that have a half-life and will eventually be broken down, there is no method for eliminating phage once it is inside the body.

DIF: Difficult REF: 14.5 OBJ: 14.5c Discuss the prospects of phage therapy to control infectious diseases.

MSC: Evaluating 9. Explain the disappearing microbiota hypothesis and how it can explain why individuals who attended day care as adolescents tend to suffer fewer allergies than individuals who did not.

ANS: The disappearing microbiota hypothesis, or the hygiene hypothesis, states that because of modern human activities, we are not exposed to as many organisms early in life as we have been in the past.

As a result, our immune systems do not have a chance to recognize organisms as nonpathogenic. This leads to an immune system that is hypersensitive due to lack of training from normal organisms, leading to conditions such as allergies. Individuals who attend day care will be exposed to a wider variety of organisms and are therefore less likely to develop allergies from disappearing microbiota than individuals who do not attend day care.

DIF: Difficult REF: 14.5 OBJ: 14.5d Explain the disappearing microbiota hypothesis.

MSC: Evaluating

10. CASE HISTORY Hiroshi, a 19-year-old college student, arrived at the emergency department complaining of a fever and lethargy that started the previous evening. He originally suspected that the symptoms were due to a hangover from a fraternity party held two days earlier. However, Hiroshi became alarmed when turning his head became painful and when tiny red blotches suddenly appeared on his skin. The physician recognized this as a petechial rash (red spots on the skin that do not blanch, or turn white, when pressed). Blood cultures were obtained, and Hiroshi underwent a lumbar puncture to obtain cerebrospinal fluid (CSF) for culture. He was immediately admitted to the hospital and treated with intravenous antibiotics. The next day, blood and CSF cultures grew a deadly Gram-negative diplococcus—Neisseria meningitidis. Hiroshi had bacterial meningitis.

Explain the natural barrier Neisseria meningitidis must have crossed in order to result in Hiroshi’s meningitis. Briefly, how does this barrier serve as an immune defense so effective some people can be asymptomatic carriers of this bacterium?

ANS: The blood–brain barrier (BBB)—in brain capillaries, endothelial cells form extremely tight junctions with no breaks for leakage. These junctions, which block the passage of most things except for very small molecules, are a crucial component of the blood–brain barrier. Brain endothelial cells also contain few intracellular vesicles, the lack of which adds to the barrier. The blood–brain barrier makes it very difficult for most pathogens to penetrate into the brain and keeps any microbiome organism that accidentally enters the bloodstream from gaining access to the central nervous system.

DIF: Easy REF: Case History 14.2 OBJ: 14.3b Explain the function of tight junctions in preventing infection.

MSC: Understanding 11. CASE HISTORY A tiny 1-kg (2.2-pound) female neonate (newborn) was born two months premature. The baby had extreme difficulty breathing and had to be intubated (a breathing tube inserted). The mother, at the time of admission, had complained of mild diarrhea and abnormal abdominal pain unrelated to her pregnancy. The infectious disease doctor who was called in to consult on the case immediately recognized the likely problem and ordered blood cultures be performed on the infant. The infant was also started on intravenous antibiotics. Two days later, the lab reported finding a Gram-positive bacillus—Listeria monocytogenes—in the infant’s blood. This same organism was the cause of the mother’s diarrhea. The mother had unwittingly ingested some unpasteurized cheese contaminated with this pathogen and developed listeriosis. The organism entered the mother’s bloodstream and was transmitted across the placenta to the fetus prior to birth.

The maternofetal or placental barrier is a mechanism that helps to protect the fetus from infection during its development. The adult human has several regions with similar levels of innate resistance to pathogen transfer. Compare and contrast at least one additional barrier that separates the natural microbiome from its host to the maternofetal barrier.

ANS: The blood–brain barrier is the most likely choice, and has a great many similarities with regard to protection of a site that cannot be effectively protected by a full adaptive immune response. However, other options do exist—for example, skin.

DIF: Easy

REF: Case History 14.3

OBJ: 14.3a List and compare the various barriers that separate the microbiome from its host.

MSC: Analyzing

Chapter 15: The Immune System: Inflammation and Innate Immunity LEARNING OBJECTIVES 15.1a Distinguish between innate immunity and adaptive immunity.

15.1b Describe the various cells and organs that constitute the immune system.

15.1c Discuss the white blood cell count differential and its role in diagnosing infectious disease.

15.2a Describe the physical barriers to infection.

15.2b Explain the basic roles of SALT, GALT, and M cells in innate immunity.

15.2c Describe chemical barriers employed by cells of the innate immune system.

15.3a List the five cardinal signs of inflammation.

15.3b Outline the process of inflammation.

15.3c Describe the roles of vasoactive factors and cytokines.

15.3d Differentiate acute from chronic inflammation.

15.4a Describe how phagocytes recognize foreign cells.

15.4b Explain the mechanisms phagocytes use to kill engulfed cells.

15.4c List some ways pathogens avoid the consequences of phagocytosis.

15.4d Discuss how our body ends the inflammatory process.

15.5a Describe the host-specific, antimicrobial function of interferons.

15.5b Explain how natural killer cells first recognize and then kill infected host cells.

15.5c Discuss Toll-like and NOD-like receptors and their contribution to innate immunity.

15.6a Explain fever and its cause.

15.6b Describe the advantages and disadvantages of fever.

15.7a Define complement.

15.7b Distinguish between the classical, alternative, and lectin pathways of complement activation.

15.7c Discuss the role of complement in host defense.

MULTIPLE CHOICE 1. Bacterial cells may be phagocytized and processed for presentation by a. erythrocytes. c. T cells. b. macrophages. d. mast cells.

ANS: B DIF: Easy REF: 15.1 OBJ: 15.1b Describe the various cells and organs that constitute the immune system.

MSC: Understanding 2. Macrophages arise from which of the following? a. neutrophils c. eosinophils b. monocytes d. basophils ANS: B DIF: Easy REF: 15.1 OBJ: 15.1b Describe the various cells and organs that constitute the immune system.

MSC: Remembering 3. An immune response that is nonspecific is referred to as ________ immunity. a. innate c. humoral

b. adaptive

d. cell-mediated

ANS: A DIF: Easy REF: 15.1 OBJ: 15.1a Distinguish between innate immunity and adaptive immunity.

MSC: Remembering 4. Which of the following is NOT an example of a white blood cell (WBC)? a. mast cell c. monocyte b. macrophage d. erythrocyte ANS: D DIF: Moderate REF: 15.1 OBJ: 15.1c Discuss the white blood cell count differential and its role in diagnosing infectious disease.

MSC: Understanding 5. Which of the following is NOT an example of a physical barrier to infection? a. skin c. defensins b. lungs d. mucosal membranes ANS: C DIF: Moderate REF: 15.2 OBJ: 15.2a Describe the physical barriers to infection.

MSC: Understanding

6. A specialized macrophage located in skin-associated lymphoid tissue (SALT) is called a(n) a. monocyte. c. dendritic cell. b. alveolar macrophage. d. Langerhans cell.

ANS: D DIF: Easy REF: 15.2 OBJ: 15.2b Explain the basic roles of SALT, GALT, and M cells in innate immunity.

MSC: Remembering 7. Lysozyme is an example of a(n) a. chemical barrier. b. physical barrier.

c. defensin. d. adaptive immune response.

ANS: A DIF: Easy REF: 15.2 OBJ: 15.2c Describe chemical barriers employed by cells of the innate immune system.

MSC: Remembering 8. Which of the following is NOT a cardinal sign of inflammation? a. heat c. pain b. edema d. pus formation ANS: D DIF: Easy REF: 15.3 OBJ: 15.3a List the five cardinal signs of inflammation.

MSC: Understanding

9. Small protein molecules secreted by macrophages are called a. vasoactive factors. c. selectins. b. cytokines. d. bradykinin.

ANS: B DIF: Easy REF: 15.3 OBJ: 15.3b Outline the process of inflammation.

MSC: Remembering

10. A child falls and suffers a deep cut on her leg. Which of the following defense mechanisms will participate in eliminating contaminating microbes? a. skin normal flora c. Langerhans cells b. lysozyme d. acidic skin secretions

ANS: C DIF: Moderate REF: 15.2 OBJ: 15.2a Describe the physical barriers to infection.

MSC: Analyzing

11. Which of the following statements is true? a. Type I and type II interferons have the same effect on the body. b. Interferon-alpha promotes phagocytosis. c. Type II interferons increase MHC antigens on the surface of macrophages. d. Interferon-gamma is a type I interferon.

ANS: C DIF: Difficult REF: 15.5 OBJ: 15.5a Describe the host-specific, antimicrobial function of interferons.

MSC: Analyzing 12. The classical, alternative, and lectin complement pathways all converge with the activation of a. C1. c. C3. b. C2. d. C5.

ANS: C DIF: Moderate REF: 15.7 OBJ: 15.7b Distinguish between the classical, alternative, and lectin pathways of complement activation.

MSC: Understanding 13. Vasodilation promoted by the release of vasoactive factors from macrophages leads to a. stimulation of local nerve endings, causing pain. b. decrease of fluid accumulation at the site. c. loss of heat to the affected area. d. decrease of blood flow to the affected area.

ANS: A DIF: Easy REF: 15.3 OBJ: 15.3c Describe the roles of vasoactive factors and cytokines.

MSC: Understanding 14. A consequence of chronic inflammation for the host is the formation of a a. boil. c. abscess. b. granuloma. d. cyst.

ANS: B DIF: Easy REF: 15.3 OBJ: 15.3d Differentiate acute from chronic inflammation.

MSC: Understanding

15. Which of the following statements is true? a. Macrophages interact with inhibitory glycoproteins to recognize self. b. Phagocytosis is a specific immune response. c. Opsonization prevents phagocytosis. d. Capsules enhance phagocytosis.

ANS: A DIF: Difficult REF: 15.4 OBJ: 15.4a Describe how phagocytes recognize foreign cells.

MSC: Analyzing

16. Penicillin interferes with bacterial cell wall synthesis. Which of the following interferes with the bacterial cell wall function inside the phagolysosome? a. lactoferrin c. lysozyme b. defensins d. oxygen radicals ANS: C DIF: Moderate REF: 15.4 OBJ: 15.4b Explain the mechanisms phagocytes use to kill engulfed cells.

MSC: Applying

17. An example of oxygen-dependent killing is a. lactoferrin. b. superoxide ion.

c. lysozyme. d. defensins.

ANS: B DIF: Easy REF: 15.4 OBJ: 15.4b Explain the mechanisms phagocytes use to kill engulfed cells.

MSC: Remembering 18. All of the following are true regarding NK cells EXCEPT that they a. are a type of lymphocyte. b. have the ability to kill infected host cells. c. destroy cells via phagocytosis. d. release toxic substances that induce cellular death.

ANS: C DIF: Difficult REF: 15.5 OBJ: 15.5b Explain how natural killer cells first recognize and then kill infected host cells.

MSC: Analyzing 19. All of the following are mechanisms to avoid digestion by phagocytes EXCEPT a. bacterial capsules. c. escape from the phagolysosome. b. formation of phagolysosomes. d. surviving inside the phagolysosome.

ANS: B DIF: Easy REF: 15.4 OBJ: 15.4c List some ways pathogens avoid the consequences of phagocytosis.

MSC: Analyzing 20. Once the inflammatory process is complete, neutrophils undergo a. phagocytosis. c. apoptosis. b. oxidative burst. d. opsonization.

ANS: C DIF: Easy REF: 15.4 OBJ: 15.4d Discuss how our body ends the inflammatory process.

MSC: Remembering 21. TLRs attach to all of the following EXCEPT a. flagellin. b. lipopolysaccharide.

c. peptidoglycan. d. cytokines.

ANS: D DIF: Moderate REF: 15.5 OBJ: 15.5c Discuss Toll-like and NOD-like receptors and their contribution to innate immunity.

MSC: Understanding 22. All of the following is true regarding a fever EXCEPT that a. the use of fever reducers helps to speed recovery. b. a fever creates an unfavorable environment for microbial growth. c. substances that cause a fever are known as pyrogens. d. thermoregulation is maintained by the hypothalamus.

ANS: A DIF: Moderate REF: 15.6 OBJ: 15.6b Describe the advantages and disadvantages of fever.

MSC: Understanding 23. All of the following occur during a fever. What is the first step? a. Prostaglandins are produced. b. Pyrogenic cytokines bind to receptors on the hypothalamus. c. Body temperature is reset to where the body thinks it is cool.

d. Involuntary muscle contractions generate heat.

ANS: B DIF: Moderate OBJ: 15.6a Explain fever and its cause.

REF: 15.6 MSC: Applying

24. The cascade of 20 serum proteins that attack bacterial invaders is called a. phagocytosis. c. a complement. b. opsonization. d. an interferon.

ANS: C DIF: Easy MSC: Remembering

REF: 15.7

OBJ: 15.7a Define complement.

25. The figure below displays the process of phagocytosis. If the lysosome did not fuse with the phagosome, the pathogen would

a. b. c. d.

not be ingested by the phagocyte. be digested in the phagosome. survive unharmed inside the phagosome. render the phagocyte paralyzed.

ANS: C DIF: Moderate REF: 15.4 OBJ: 15.4c List some ways pathogens avoid the consequences of phagocytosis.

MSC: Applying 26. The figure below shows the process of opsonization. This process belongs to which type of immunity?

a. innate b. adaptive

c. complement d. phagocytosis

ANS: B DIF: Moderate REF: 15.4 OBJ: 15.4b Explain the mechanisms phagocytes use to kill engulfed cells.

MSC: Understanding 27. The complement cascade produces all of the following outcomes EXCEPT a. creating pores in bacterial membranes. c. attracting white blood cells. b. increasing phagocytosis. d. decreasing inflammation.

ANS: D MSC: Analyzing

DIF: Moderate

REF: 15.7

OBJ: 15.7a Define complement.

28. Which of the following statements about the classical pathway of complement activation is FALSE? a. The C3 protein is not involved in the classical pathway. b. C1 is the first protein activated in the pathway. c. Cleavage of complement proteins increases inflammation. d. The classical pathway is activated by antibodies binding to bacterial cells.

ANS: A DIF: Moderate REF: 15.7 OBJ: 15.7b Distinguish between the classical, alternative, and lectin pathways of complement activation.

MSC: Analyzing 29. Which nonspecific defense mechanism is mismatched with its associated body structure or body fluid? a. lysozyme—tears c. keratin—skin b. acidic pH—stomach d. Langerhans cell—lungs ANS: D DIF: Moderate REF: 15.2 OBJ: 15.2c Describe chemical barriers employed by cells of the innate immune system.

MSC: Understanding 30. All of the following are components of the inflammatory process EXCEPT a. extravasation. c. antibody synthesis. b. release of cytokines. d. vasodilation.

ANS: C DIF: Moderate REF: 15.3 OBJ: 15.3b Outline the process of inflammation.

MSC: Analyzing

31. The figure below highlights the mechanism of extravasation in the inflammatory process. Neutrophils that do NOT produce integrins will

a. b. c. d.

bind to ICAM-1 and VCAM-1. be able to bind to the vascular wall. undergo extravasation. not lock onto endothelial adhesion molecules.

ANS: A DIF: Difficult REF: 15.3 OBJ: 15.3c Describe the roles of vasoactive factors and cytokines.

MSC: Applying 32. The figure below highlights the process of complement activation. The classical pathway can be activated in two ways: antibody-dependent binding and by

a. C-reactive protein. b. cytokines.

c. factor K. d. lectin.

ANS: A DIF: Difficult REF: 15.7 OBJ: 15.7b Distinguish between the classical, alternative, and lectin pathways of complement activation.

MSC: Applying 33. Which pathway is the alternative pathway in the figure below?

a. Pathway 1 b. Pathway 2

c. Pathway 3 d. none

ANS: A DIF: Easy REF: 15.7 OBJ: 15.7b Distinguish between the classical, alternative, and lectin pathways of complement activation.

MSC: Understanding 34. Innate immunity includes all of the following EXCEPT a. phagocytosis. c. activation of complement. b. inflammation. d. production of antibody.

ANS: D DIF: Easy REF: 15.1 OBJ: 15.1a Distinguish between innate immunity and adaptive immunity.

MSC: Understanding 35. A differential cell count is used to determine each of the following EXCEPT the a. total number of white blood cells. b. numbers of each type of white blood cells. c. number of red blood cells.

d. presence of cancer.

ANS: C DIF: Easy REF: 15.1 OBJ: 15.1c Discuss the white blood cell count differential and its role in diagnosing infectious disease.

MSC: Understanding 36. Using the data from the differential white blood cell count table below, which patient profile displays a parasitic infection?

a. Patient 1 b. Patient 2

c. Patient 3 d. None

ANS: B DIF: Difficult REF: 15.1 OBJ: 15.1c Discuss the white blood cell count differential and its role in diagnosing infectious disease.

MSC: Applying 37. Gut-associated lymphoid tissue (GALT) includes all of the following EXCEPT a. tonsils. c. M cells. b. adenoids. d. alveolar macrophages.

ANS: D DIF: Moderate REF: 15.2 OBJ: 15.2b Explain the basic roles of SALT, GALT, and M cells in innate immunity.

MSC: Understanding 38. Body chills are a sign that a. body temperature is falling. b. body temperature is rising.

ANS: B DIF: Moderate OBJ: 15.6a Explain fever and its cause.

c. body temperature is not changing. d. blood vessels are dilating.

REF: 15.6 MSC: Understanding

39. According to the table below, which type(s) of interferon(s) work(s) to create an antiviral state in host cells?

a. Type 1 b. Type 2

c. both d. neither

ANS: A DIF: Moderate REF: 15.5 OBJ: 15.5a Describe the host-specific, antimicrobial function of interferons.

MSC: Applying 40. According to the table below, which type(s) of interferon(s) would induce an increase in MHC expression from host cells?

a. Type 1 b. Type 2

c. both d. neither

ANS: B DIF: Moderate REF: 15.5 OBJ: 15.5a Describe the host-specific, antimicrobial function of interferons.

MSC: Applying 41. CASE HISTORY Bobby, an 11-year-old boy from Nebraska, suffered his entire life from recurring life-threatening infections caused mostly by the Gram-positive bacteria Staphylococcus aureus and Streptococcus pneumoniae. His infections included meningitis, osteomyelitis (bone infection), and arthritis caused by S. pneumoniae, as well as episodes of septicemia and osteomyelitis and recurrent boils caused by S. aureus. Tests to find a cause for these recurring infections were initially disappointing. The results of all standard immunological tests were normal, including T-cell lymphocyte responses, blood antibody levels, and antibody responses to injected proteins and polysaccharides. This means his adaptive immune system was functioning. The numbers of monocytes/macrophages in his blood were also normal. However, pro-inflammatory cytokine levels (indicators of innate immunity) measured during the latest infection were considerably lower than expected. Further tests proved that Bobby inherited an innate immune defect in Toll-like receptor signaling. Currently, there is no cure for this immunodeficiency. To stem the tide of infections, Bobby was placed on long-term, preventive antibiotic treatment.

Which of the following best describes the portion of a pathogen recognized by Toll-like receptors? a. specific antigens, particularly those on the surface of Gram-positive pathogens such as Streptococci b. repeating nonself motifs such as peptidoglycan from Gram-positive organisms c. major histocompatibility complex molecules on the surface of pathogenic cells d. Toll-like receptors on the surface of pathogens, recognized by MAMPs on our immune cells ANS: B DIF: Moderate REF: Case History 15.2 OBJ: 15.4a Describe how phagocytes recognize foreign cells.

MSC: Applying

COMPLETION 1. A clinical test that counts the total number of white blood cells and identifies their various cell types is called a ________.

ANS: white blood cell differential DIF: Easy REF: 15.1 OBJ: 15.1c Discuss the white blood cell count differential and its role in diagnosing infectious disease.

MSC: Remembering 2. Movement of neutrophils out of blood vessels and into infected tissue is called ________.

ANS: extravasation DIF: Easy REF: 15.3 MSC: Remembering

OBJ: 15.3a List the five cardinal signs of inflammation.

3. Substances that cause fever are known as ________.

ANS: pyrogens DIF: Easy REF: 15.6 MSC: Remembering

OBJ: 15.6a Explain fever and its cause.

4. Toll-like receptors recognize ________ on pathogenic microorganisms.

ANS: microbe-associated molecular patterns; MAMPs DIF: Easy REF: 15.5 OBJ: 15.5c Discuss Toll-like and NOD-like receptors and their contribution to innate immunity.

MSC: Remembering 5. Cytokines that have chemotactic properties are called ________.

ANS: chemokines DIF: Easy REF: 15.3 OBJ: 15.3c Describe the roles of vasoactive factors and cytokines.

MSC: Remembering SHORT ANSWER 1. Draw, label, and explain the process of phagocytosis including the main steps in the pathway (adherence, ingestion, and phagolysome formation/destruction). What would happen if an organism was able to avoid phagocytosis?

ANS: Adherence: Bacterium binds to the surface of the phagocytic cell.

Ingestion: Bacterial cell is taken into a phagosome within the macrophage.

Phagolysome formation: Once inside the phagosome it fuses with a lysosome and deposits enzymes into the now formed phagolysosome. These enzymes cleave macromolecules and generate reactive oxygen species.

Destruction: Enzymes and reactive oxygen radicals destroy the organism by targeting the cell wall and membrane. Once destroyed, the organism is released from the phagocytic cell.

If an organism is able to escape phagocytosis, then it would be difficult to prime the adaptive immune system because microbial peptides would not be displayed on host MHC molecules for presentation to B and T cells.

DIF: Difficult REF: 15.4 OBJ: 15.4b Explain the mechanisms phagocytes use to kill engulfed cells.

MSC: Applying 2. There are two general types of interferons, type I and type II. Describe how type I interferons work to prevent the host from infection.

ANS: Type 1 interferons have high antiviral potency and consist of INF-alpha, INF-beta, and INF-omega.

Type 1 interferons bind to specific receptors on infected host cells and induce the synthesis of two classes of proteins: dsRNA-activated endoribonucleases, which act to cleave viral DNA and protein kinases (PKRs) that phosphorylate, and inactive eIF2, which is required to translate viral DNA. DIF: Difficult REF: 15.5 OBJ: 15.5a Describe the host-specific, antimicrobial function of interferons.

MSC: Applying 3. Compare and contrast the innate and adaptive immune responses including specificity, two cell types for each, and time frame for response and production of memory cells.

ANS: Innate immunity is constantly “on” and is nonspecific. This first line of defense is composed of lymphatic tissue, physical and chemical barriers, and phagocytic cells. The innate immune system protects the host while the adaptive immune system is activated.

Adaptive immunity takes several days to turn on and is specific to the invading microbe. This arm of the immune system is composed of B cells, T cells, and antibodies. Once generated, this type of immune response turns on more quickly when encountering the pathogen for a second time because memory cells were generated.

DIF: Difficult REF: 15.1 OBJ: 15.1a Distinguish between innate immunity and adaptive immunity.

MSC: Applying 4. Peyer’s patches are located within gut-associated lymphoid tissue (GALT). Explain the function of Peyer’s patches in regard to their function in the immune system.

ANS: M cells are important cells of the Peyer’s patches and are wedged between epithelial cells in the intestines. M cells pick up microbes from the intestines and present them to immune cells located on the basolateral side of the cell. Macrophages gather here and “collect” the organisms to present to the immune system.

DIF: Difficult REF: 15.2 OBJ: 15.2b Explain the basic roles of SALT, GALT, and M cells in innate immunity.

MSC: Applying 5. Explain how each of the following avoids being killed by phagocytes: a. Shigella dysenteriae b. Salmonella typhimurium c. Listeria monocytogenes ANS: Phagocytosis is very effective at killing microbes. Some pathogens have evolved ways to avoid being killed by phagocytosis. a. S. dysenteriae enters the host phagocytic cells and triggers the cell to undergo apoptosis. This saves the bacterial cell from being killed by phagocytosis. b. S. typhimurium stays within the phagosome; however, it secretes proteins that prevent fusion with the lysosome. c. L. monocytogenes is able to escape the phagosome after ingestion by the macrophage before lysosome fusion. This allows the organism to enter into the cytoplasm of the host cell and replicate freely.

DIF: Difficult REF: 15.4 OBJ: 15.4c List some ways pathogens avoid the consequences of phagocytosis.

MSC: Applying 6. CASE HISTORY Constance, a seven-month-old female, suffered from recurrent infections since the age of two weeks.

She was frequently admitted to the hospital for Staphylococcus aureus sepsis (blood infection), hepatosplenomegaly (enlarged liver and spleen), oral thrush caused by Candida albicans, and poor weight gain. Repeated treatments with different antibiotics only temporarily resolved her infections.

Two days ago, her alarmed mother and father once again brought Constance to the emergency department at the University of Chicago Medical Center. Constance was lethargic, did not move much, and had a high fever. She also struggled for breath. Her blood work revealed high white blood cell counts (59,000/mm3; normal is 4,000–11,000) with a higher than normal level of neutrophils in her blood (neutrophilia). A chest X-ray showed inflammation in both lungs. It was no surprise, then, when the lab technician reported finding Staphylococcus aureus in Constance’s blood. Her doctor ordered intravenous antibiotic therapy and was determined to find the cause of these repeated infections. He suspected a serious defect in Constance’s immune system. Laboratory analyses found that her lymphocyte numbers, overall serum immunoglobulin (antibody) levels, and liver and kidney functions were all normal. No help there. Then flow cytometry analysis of surface proteins present on Constance’s peripheral blood neutrophils revealed a complete absence of critically important membrane proteins. The doctor’s heart sank. It was not good news.

Constance’s neutrophils are unable to adhere to the walls of her blood vessels. In the normal process of inflammation, however, describe the next steps for these neutrophils.

ANS: Neutrophils will move from tissue into vessels and toward the site of infection (extravasation). Once at the infection site, the neutrophils begin engulfing microbes (phagocytosis). The white pus associated with an infection is teeming with these white blood cells.

DIF: Easy REF: Case History 15.1 OBJ: 15.3b Outline the process of inflammation.

7. CASE HISTORY

MSC: Analyzing

Bobby, an 11-year-old boy from Nebraska, suffered his entire life from recurring life-threatening infections caused mostly by the Gram-positive bacteria Staphylococcus aureus and Streptococcus pneumoniae. His infections included meningitis, osteomyelitis (bone infection), and arthritis caused by S. pneumoniae, as well as episodes of septicemia and osteomyelitis and recurrent boils caused by S. aureus. Tests to find a cause for these recurring infections were initially disappointing. The results of all standard immunological tests were normal, including T-cell lymphocyte responses, blood antibody levels, and antibody responses to injected proteins and polysaccharides. This means his adaptive immune system was functioning. The numbers of monocytes/macrophages in his blood were also normal. However, pro-inflammatory cytokine levels (indicators of innate immunity) measured during the latest infection were considerably lower than expected. Further tests proved that Bobby inherited an innate immune defect in Toll-like receptor signaling. Currently, there is no cure for this immunodeficiency. To stem the tide of infections, Bobby was placed on long-term, preventive antibiotic treatment.

How are NOD-like receptors similar to and different from Toll-like receptors? Would Bobby’s immune deficiency manifest identically if he had a deficit in NLRs rather than TLRs? ANS: NOD-like receptors are also pattern recognition receptors for MAMPs; however, they tend to induce pro-inflammatory cytokine pathways in response to intracellular stimulus, as they are not membrane bound (as TLRs are). The specific manifestations of the two disorders are not necessarily clear from the level of detail in the text, but students should be able to indicate that susceptibility to intracellular organisms would likely be increased in NLR-deficient patients.

DIF: Difficult REF: Case History 15.2 OBJ: 15.5c Discuss Toll-like and NOD-like receptors and their contribution to innate immunity.

MSC: Evaluating

Chapter 16: The Immune System: Adaptive Immunity LEARNING OBJECTIVES 16.1a Differentiate humoral immunity from cellular immunity and the basic roles of B cells and T cells in those systems.

16.1b Explain the relationships between antigens, epitopes, immunogens, and haptens.

16.1c Discuss the concept of a clonal immunological response to an epitope.

16.1d Define antigen presentation and antigen-presenting cell.

16.2a Describe what makes one antigen more immunogenic than another.

16.2b Discuss immunological specificity and its application to vaccine development.

16.3a Distinguish immunoglobulin proteins from the immunoglobulin family of proteins.

16.3b Diagram the structures and superstructures of antibodies and discuss their functions.

16.3c Differentiate between the isotype, allotype, and idiotype of an antibody.

16.4a Explain the difference between primary and secondary antibody responses.

16.4b Discuss B-cell differentiation and the role of the B-cell receptor.

16.4c Summarize how the immune system generates vast antibody diversity.

16.4d Describe the role of memory B cells during an antibody response.

16.5a Explain the three major types of T cells.

16.5b Discuss the role of major histocompatibility proteins in the adaptive immune response.

16.5c Discuss the two routes of antigen processing and presentation.

16.5d Describe processes that minimize autoimmunity.

16.6a Describe a T-cell receptor (TCR), and explain its role in T-cell activation.

16.6b Explain how a TCR also participates in B-cell activation.

16.6c Discuss CD40 and CD40 ligand interaction.

16.6d Explain why memory B cells do not always need T-cell help for activation.

16.7a Explain how cytotoxic T cells become activated.

16.7b Discuss how activated TC cells recognize their target host cells.

16.7c Describe the role of cytokines in directing adaptive immunity toward humoral or cytotoxic responses.

16.7d Distinguish antigens from superantigens.

16.7e Diagram the basic ways that pathogens can avoid the immune system.

MULTIPLE CHOICE 1. A microbe is ingested and broken into fragments by an antigen-presenting cell (APC). Which of the following would be expected to occur? a. B cells will bind to antigens on the surface of the APC. b. B cells will release cytokines to activate T cells. c. Plasma cells will release cytokines to activate the APC. d. T cells will bind to antigens on the surface of the APC. ANS: D DIF: Moderate REF: 16.1 OBJ: 16.1a Differentiate humoral immunity from cellular immunity and the basic roles of B cells and T cells in those systems.

MSC: Applying 2. What step would have preceded the figure shown below?

a. b. c. d.

The B cell would have recognized antigen bound to an antigen-presenting cell.

The T cell would have recognized antigen bound to an antigen-presenting cell.

The B cell would have gone through clonal expansion.

The T cell would have differentiated into plasma cells.

ANS: B DIF: Moderate REF: 16.1 OBJ: 16.1a Differentiate humoral immunity from cellular immunity and the basic roles of B cells and T cells in those systems.

MSC: Applying 3. The figure shown below illustrates clonal expansion of activated B cells. What are the two cell types produced by this cell line?

a. b. c. d.

plasma cells and memory B cells antigen-presenting cells and memory T cells activated T cells and plasma cells memory B cells and dendritic cells

ANS: A DIF: Moderate REF: 16.1 OBJ: 16.1a Differentiate humoral immunity from cellular immunity and the basic roles of B cells and T cells in those systems.

MSC: Understanding 4. Which of the following statements correctly describes the molecules that elicit an immune response? a. Antigens are small molecules that must be bound to an immunogen to elicit an immune response. b. Small segments of an antigen that elicit an immune response are called epitopes. c. Haptens are proteins that elicit the synthesis of antibodies and are also known as antigens. d. Immunogens are small segments of antigens that are recognized by the immune system.

ANS: B DIF: Moderate REF: 16.1 OBJ: 16.1b Explain the relationships between antigens, epitopes, immunogens, and haptens.

MSC: Understanding 5. Which of the following accurately describes how a foreign molecule leads to the production of antibody?

a. Individual epitopes on an antigen are recognized and a single antibody is produced for each epitope. b. The immune system recognizes whole microbes and responds by secreting a single antibody against the microbe. c. The immune system recognizes individual haptens on an antigen and secretes several antibodies directed against that hapten. d. Groups of epitopes on an antigen are recognized and a single antibody is produced for each group.

ANS: A DIF: Moderate REF: 16.1 OBJ: 16.1b Explain the relationships between antigens, epitopes, immunogens, and haptens.

MSC: Applying 6. The figure shown below illustrates a bacterial cell that

a. b. c. d.

acts as an antigen. is broken down into many antigens. is producing antibodies in response to antigens. has a single epitope.

ANS: B DIF: Easy REF: 16.1 OBJ: 16.1c Discuss the concept of a clonal immunological response to an epitope.

MSC: Understanding 7. Clonal expansion of B cells occurs when a(n) a. antigen-presenting cell binds to a single B cell. b. helper T cell secretes antibody onto a single B cell. c. single B cell becomes activated when its receptor binds to a single epitope. d. memory B cell attaches onto an antigen-presenting cell.

ANS: C DIF: Moderate REF: 16.1 OBJ: 16.1c Discuss the concept of a clonal immunological response to an epitope.

MSC: Applying 8. Which of the following cell types is considered a “nonprofessional” antigen-presenting cell? a. fibroblast c. dendritic cell b. macrophage d. B cell ANS: A DIF: Easy REF: 16.1 OBJ: 16.1d Define antigen presentation and antigen-presenting cell.

MSC: Remembering 9. An antigen-presenting cell (APC) presents antigen to a. macrophages to stimulate the synthesis of antibodies.

b. B cells to stimulate the formation of memory B cells. c. memory T cells to stimulate the synthesis of cytokines. d. helper T cells to activate the T cells during a cellular response.

ANS: D DIF: Moderate REF: 16.1 OBJ: 16.1d Define antigen presentation and antigen-presenting cell.

MSC: Understanding 10. Which of the following would be expected to elicit the largest production of antibodies? a. haptens floating freely within plasma b. a complex protein with many different epitopes c. a polysaccharide with several identical segments d. a small lipid ANS: B DIF: Moderate REF: 16.2 OBJ: 16.2a Describe what makes one antigen more immunogenic than another.

MSC: Analyzing 11. An injection of killed or attenuated Salmonella typhi, the causative agent of typhoid fever, would be expected to protect an individual by a. causing the individual to have a mild case of typhoid fever, but protecting against future cases of typhoid fever. b. providing antigens recognizable by the immune system, allowing the formation of memory cells that will prevent typhoid fever in the future. c. providing cross-protection to prevent several diseases caused by different bacteria. d. providing the individual with premade antibodies capable of binding to and inactivating Salmonella typhi.

ANS: B DIF: Difficult REF: 16.2 OBJ: 16.2b Discuss immunological specificity and its application to vaccine development.

MSC: Analyzing 12. Which of the following statements is an example of a situation in which cross-protection will occur? a. A vaccine is administered for one of two viruses that share epitopes. b. A single virus triggers a response from both B cells and T cells. c. An antigen forms a cross-link between two antibodies. d. A combination vaccine is administered to provide protection against three viruses.

ANS: A DIF: Difficult REF: 16.2 OBJ: 16.2b Discuss immunological specificity and its application to vaccine development.

MSC: Applying 13. The immunoglobulin superfamily of proteins includes a. immunoglobulins only. b. immunoglobulins, major histocompatibility complex, and B- and T-cell receptors. c. major histocompatibility complex and B- and T-cell receptors only. d. IgA, IgG, IgM, IgE, and IgD only.

ANS: B DIF: Easy REF: 16.3 OBJ: 16.3a Distinguish immunoglobulin proteins from the immunoglobulin family of proteins.

MSC: Remembering 14. The antigen-binding site on an antibody a. is composed of light chains only. b. contains constant amino acid sequences within each class.

c. contains highly variable amino acid sequences. d. is composed of heavy chains only.

ANS: C DIF: Moderate REF: 16.3 OBJ: 16.3b Diagram the structures and superstructures of antibodies and discuss their functions.

MSC: Understanding 15. The figure below shows the structure of an ________ antibody.

a. IgG b. IgA

c. IgM d. IgE

ANS: C DIF: Easy REF: 16.3 OBJ: 16.3b Diagram the structures and superstructures of antibodies and discuss their functions.

MSC: Understanding 16. A newborn receives passive immunity from its mother with the main antibody isotype being a. IgG. c. IgD. b. IgM. d. IgE. ANS: A DIF: Easy REF: 16.3 OBJ: 16.3b Diagram the structures and superstructures of antibodies and discuss their functions.

MSC: Remembering 17. Which of the following scenarios is an example of an allotypic difference? a. A single amino acid change gives rise to a new form of IgG antibody in humans. b. Humans and dogs have slightly different immunoglobulins. c. A human is able to generate antigen specificity by rearranging genes. d. There are five major classes of immunoglobulins within an individual.

ANS: A DIF: Difficult REF: 16.3 OBJ: 16.3c Differentiate between the isotype, allotype, and idiotype of an antibody.

MSC: Evaluating 18. IgG, IgA, IgM, IgD, and IgE are all examples of a. antigens. c. isotypes. b. idiotypes. d. allotypes.

ANS: C DIF: Easy REF: 16.3 OBJ: 16.3c Differentiate between the isotype, allotype, and idiotype of an antibody.

MSC: Understanding 19. When comparing the primary and secondary immune responses, ________ titer levels are ________ during a ________ immune response. a. IgM; much higher; secondary b. IgG; much higher; secondary c. IgM; higher than IgG titer levels; primary d. IgM; higher than IgG titer levels; secondary ANS: B DIF: Moderate REF: 16.4 OBJ: 16.4a Explain the difference between primary and secondary antibody responses.

MSC: Analyzing 20. Which two antibody classes are displayed on the surface of naïve B cells? a. IgG and IgD c. IgE and IgM b. IgE and IgD d. IgM and IgD ANS: D DIF: Moderate REF: 16.4 OBJ: 16.4b Discuss B-cell differentiation and the role of the B-cell receptor.

MSC: Remembering 21. The process illustrated in the figure below is best described as

a. capping. b. T-cell-dependent activation.

c. class switching. d. clonal selection.

ANS: A DIF: Easy REF: 16.4 OBJ: 16.4b Discuss B-cell differentiation and the role of the B-cell receptor.

MSC: Understanding 22. Why does B-cell proliferation and differentiation often require assistance from helper T cells? a. Capping does not occur unless epitopes are found in multiple copies. b. B cells require antigen presentation by helper T cells. c. Microbes often destroy B-cell receptors and then B cells require help from T cells. d. Helper T cells are required to move epitopes closer together for capping by B cells.

ANS: A DIF: Moderate REF: 16.4 OBJ: 16.4b Discuss B-cell differentiation and the role of the B-cell receptor.

MSC: Applying 23. Class switching is the process in which a. B cells switch from producing IgM of IgD to producing IgE, IgG, or IgA. b. formed IgM antibody pentamers break apart into IgM monomers. c. antibody released from the surface of a B cell switches to a different heavy chain. d. higher-affinity antibodies are produced upon repeated exposure to the same antigen.

ANS: A DIF: Easy REF: 16.4 OBJ: 16.4c Summarize how the immune system generates vast antibody diversity.

MSC: Understanding 24. If you had a box of 200 beads that were different shapes and you randomly chose and linked together 3 beads, you would be performing a process analogous to the way a. T cells are able to use 200 genes to produce 3 receptor types. b. 200 B cells are able to produce 3 different antibodies. c. antigens are processed by antigen-presenting cells. d. antibody diversity is created within our bodies.

ANS: D DIF: Moderate REF: 16.4 OBJ: 16.4c Summarize how the immune system generates vast antibody diversity.

MSC: Analyzing 25. Memory B cells are able to persist for many years because they a. are continuously stimulated by cytokines released from helper T cells. b. undergo hypermutation, which allows them to survive indefinitely. c. use gene rearrangement to prevent apoptosis from occurring. d. have receptors that match with antigen producing anti-apoptosis protein.

ANS: D DIF: Moderate REF: 16.4 OBJ: 16.4d Describe the role of memory B cells during an antibody response.

MSC: Applying 26. T cells that secrete IL-4, IL-5, and IL-6 and that play a major role in helping B cells are known as ________ cells. a. Treg c. TH1 b. TH2 d. TH0 ANS: B DIF: Easy REF: 16.5 OBJ: 16.5a Explain the three major types of T cells.

MSC: Understanding

27. T cells capable of killing virus-infected and cancer cells are known as ________ cells. a. TC c. TH17 b. TH2 d. TH1 ANS: A DIF: Easy REF: 16.5 OBJ: 16.5a Explain the three major types of T cells.

28. MHC molecules are required for a. B-cell activation. b. phagocytosis of microbes.

ANS: C

DIF: Easy

MSC: Understanding

c. T-cell activation. d. proteasome degradation of viruses.

REF: 16.5

OBJ: 16.5b Discuss the role of major histocompatibility proteins in the adaptive immune response.

MSC: Understanding 29. Antigen bound by the molecule shown below would be recognized by ________ cells.

a. TC b. TH2

c. TH17 d. B

ANS: A DIF: Moderate REF: 16.5 OBJ: 16.5b Discuss the role of major histocompatibility proteins in the adaptive immune response.

MSC: Analyzing 30. Class II MHC molecules are used to present ________ antigen to ________ cells. a. intracellular; CD8 c. extracellular; CD8 b. intracellular; CD4 d. extracellular; CD4 ANS: D DIF: Moderate REF: 16.5 OBJ: 16.5b Discuss the role of major histocompatibility proteins in the adaptive immune response.

MSC: Understanding 31. Which of the following would most directly eliminate an intracellular pathogen such as a virus? a. production of antibody c. activation of cytotoxic T cells b. activation of B cells d. activation of helper T cells ANS: C DIF: Easy REF: 16.5 OBJ: 16.5c Discuss the two routes of antigen processing and presentation.

MSC: Applying 32. Almost 95% of T cells entering the thymus die when apoptosis is triggered during a. positive selection. c. antibody production. b. negative selection. d. MHC recognition.

ANS: B DIF: Easy REF: 16.5 OBJ: 16.5d Describe processes that minimize autoimmunity.

33. T-cell receptors (TCRs) are only able to bind a. peptides.

MSC: Remembering

c. polysaccharides.

b. lipids.

d. DNA.

ANS: A DIF: Moderate REF: 16.6 OBJ: 16.6a Describe a T-cell receptor (TCR), and explain its role in T-cell activation.

MSC: Understanding 34. Individuals with bare lymphocyte syndrome lack MHC II proteins. Which of the following could still occur in an individual lacking MHC II proteins? a. Helper T cells could use T-cell receptors to interact with macrophages. b. B cells could produce IgM antibodies. c. Cytotoxic T cells could become activated. d. B cells could undergo class switching independently.

ANS: B DIF: Moderate REF: 16.6 OBJ: 16.6b Explain how a TCR also participates in B-cell activation.

MSC: Applying 35. The direct consequence of a CD40 protein on a B cell binding to a CD40 ligand on a T cell is a. initiation of an intracellular signal required for B-cell activation. b. heavy-chain class switching in the B cell. c. release of IL-2 from the T cell. d. release of perforins and granzymes from the T cell.

ANS: A DIF: Difficult REF: 16.6 OBJ: 16.6c Discuss CD40 and CD40 ligand interaction.

MSC: Analyzing

36. Memory B cells become activated during the secondary immune response by a. presenting antigen bound to MHC II and binding to TH cells. b. responding to soluble IL-4 and IL-6 without direct contact with TH cells. c. binding IgM antibody on activated B cells. d. using CD40 surface proteins to attach to CD40 ligands on TH cells.

ANS: B DIF: Difficult REF: 16.6 OBJ: 16.6d Explain why memory B cells do not always need T-cell help for activation.

MSC: Applying 37. The second signal required for TC activation is a. binding of a CD28 molecule on the T cell to a B7 protein on an antigen-presenting cell. b. secretion of the cytokine IL-2 from a TH1 cell. c. binding of a CD8 molecule on the T cell to an antigen-MHC I complex on an antigenpresenting cell. d. secretion of the cytokine IL-1 from a TH0 cell.

ANS: B DIF: Moderate REF: 16.7 OBJ: 16.7a Explain how cytotoxic T cells become activated.

MSC: Applying

38. The molecule indicated on the illustration below of the first signal during the activation of a cytotoxic T cell (TC) must be

a. Class I MHC. b. Class II MHC.

c. a CD8 molecule. d. a B7 protein.

ANS: A DIF: Moderate REF: 16.7 OBJ: 16.7a Explain how cytotoxic T cells become activated.

MSC: Applying

39. The cell indicated on the illustration below has the ________ surface molecule.

a. CD4 b. Class I MHC

c. Class II MHC d. CD8

ANS: D DIF: Moderate REF: 16.7 OBJ: 16.7a Explain how cytotoxic T cells become activated.

MSC: Applying

40. Why are cytotoxic T (TC) cells more effective than antibodies at clearing viral infections? a. TC cells are able to recognize free viral particles as they circulate through lymph nodes. b. Antibodies bind weakly to antigen-MHC I complexes on antigen-presenting cells. c. Antibodies are only able to bind to extracellular antigen, and viruses tend to be intracellular. d. TC cells are activated more strongly than B cells by cytokines released by helper T cells.

ANS: C DIF: Difficult REF: 16.7 OBJ: 16.7b Discuss how activated TC cells recognize their target host cells.

MSC: Applying 41. One health risk associated with excessive cytokine release is the chance of a. severe tissue damage. c. damage to virally infected cells. b. cytokines destroying antibodies. d. inactivating mitosis.

ANS: A DIF: Easy REF: 16.7 OBJ: 16.7c Describe the role of cytokines in directing adaptive immunity toward humoral or cytotoxic responses.

MSC: Remembering

42. CASE HISTORY Nathan was a ten-month-old male who had suffered much in his short life. Since birth he had experienced recurrent serious extracellular bacterial infections, all of which were resolved by antibiotic treatment. On Christmas Day, Nathan’s mother discovered he had another high fever and a nonproductive cough (no mucus). He was also having trouble breathing. Fearing one more serious infection, Nathan’s mother rushed him to the hospital. An X-ray showed the lung infiltrate with the appearance of ground glass. A tube was placed through Nathan’s nose and into his lung, and a solution was used to wash out deep-lung contents for microscopic examination (bronchoalveolar lavage). The fluid yielded microscopic organisms. Nathan was hospitalized with pneumonia caused by Pneumocystis jirovecii, a yeastlike fungus. Although most of us have been infected with this organism, our immune systems almost always prevent disease. Finding the disease in Nathan suggested a serious immune dysfunction. An immunological workup revealed mild neutropenia (lower than normal numbers of neutrophils) but normal numbers of T and B cells, normal levels of complement, and normal complement activity. However, Nathan’s blood exhibited exceptionally high levels of IgM but very low IgG and IgA levels. The physician suspected a specific defect in Nathan’s T cells.

Based on his findings regarding antibody production, Nathan’s doctor may suspect that a mutation affecting ________ is causing Nathan’s immunodeficiency. a. CD40 c. MHCI b. CD8 d. IL10 ANS: A DIF: Moderate REF: Case History 16.2 OBJ: 16.6c Discuss CD40 and CD40 ligand interaction.

MSC: Understanding COMPLETION 1. A humoral immune response involves the production of ________.

ANS: antibodies, antibody DIF: Easy REF: 16.1 OBJ: 16.1a Differentiate humoral immunity from cellular immunity and the basic roles of B cells and T cells in those systems.

MSC: Remembering 2. Small molecules that do NOT elicit an immune response unless they are attached to immunogens are referred to as ________.

ANS: haptens DIF: Easy REF: 16.1 OBJ: 16.1b Explain the relationships between antigens, epitopes, immunogens, and haptens.

MSC: Remembering 3. Immunoglobulin proteins are also known as ________.

ANS: antibodies DIF: Easy REF: 16.3 OBJ: 16.3a Distinguish immunoglobulin proteins from the immunoglobulin family of proteins.

MSC: Remembering 4. Helper T cells display the surface antigen ________.

ANS: CD4 DIF: Easy REF: 16.5 MSC: Remembering

OBJ: 16.5a Explain the three major types of T cells.

5. Cytotoxic T cells display the surface antigen ________.

ANS: CD8 DIF: Easy REF: 16.5 MSC: Remembering

OBJ: 16.5a Explain the three major types of T cells.

6. Cells that become activated when they bind to intracellular antigen bound to class I MHC on antigenpresenting cells are known as ________ cells.

ANS: cytotoxic; TC; CD8; CD 8 DIF: Easy REF: 16.7 OBJ: 16.7a Explain how cytotoxic T cells become activated.

MSC: Understanding

7. The small peptides released by various cells that influence the direction and intensity of an immune response are known as ________.

ANS: cytokines DIF: Easy REF: 16.7 OBJ: 16.7c Describe the role of cytokines in directing adaptive immunity toward humoral or cytotoxic responses.

MSC: Remembering 8. Proteins that do NOT require antigen processing and presentation are referred to as ________.

ANS: superantigens DIF: Easy REF: 16.7 MSC: Remembering

OBJ: 16.7d Distinguish antigens from superantigens.

SHORT ANSWER 1. Bloodwork indicates that a patient who has pneumonia is actively secreting different forms of antibody against Streptococcus pneumoniae. Explain how the patient is able to respond to this pathogen by secreting more than one antibody.

ANS: Streptococcus pneumoniae is eliciting a polyclonal response. Any single B cell only responds to one epitope on an antigen. In this case, there are thousands of B cells, each responding to different epitopes. When a B cell recognizes and binds to an epitope, the B cell becomes activated and undergoes clonal expansion to produce antibody-secreting plasma cells and memory B cells.

DIF: Moderate REF: 16.1 OBJ: 16.1c Discuss the concept of a clonal immunological response to an epitope.

MSC: Applying 2. Describe the function of the major histocompatibility complex (MHC).

ANS: The major histocompatibility complex (MHC) is a membrane surface protein structure used to present antigen to T cells on the surface of cells. This system is required for T cells to recognize and bind to antigen.

DIF: Moderate REF: 16.1 OBJ: 16.1d Define antigen presentation and antigen-presenting cell.

MSC: Understanding 3. Rank the following macromolecules in terms of their antigenicity and explain your ranking: carbohydrates, proteins, lipids, and nucleic acids.

ANS: Proteins tend to make the strongest antigens. Carbohydrates are also capable of eliciting a strong immune response. Nucleic acids and lipids tend to be weaker antigens than either proteins or carbohydrates. Molecules with more complex structures, such as proteins and some carbohydrates, tend to elicit a stronger response. The relatively uniform structure and flexibility of nucleic acids and lipids tend to make them weaker antigens.

DIF: Moderate REF: 16.2 OBJ: 16.2a Describe what makes one antigen more immunogenic than another.

MSC: Analyzing 4. How do the structure and function of the F(ab) and Fc regions of an antibody differ?

ANS: The F(ab) region, made of both light and heavy chains, has a variable region used for binding antigen.

The Fc region, part of the heavy chain, is constant in its amino acid sequence. The Fc region is important for anchoring antibodies to the surface of certain host cells and for activation of complement, in some cases.

DIF: Moderate REF: 16.3 OBJ: 16.3b Diagram the structures and superstructures of antibodies and discuss their functions.

MSC: Evaluating 5. Natalia and Julia are looking through primary literature for information about antibodies. One of the articles is titled “Generating Diversity in Idiotypes.” Should they expect this article to compare different species, different individuals of the same species, or different antibodies within individuals?

Explain your answer.

ANS: This article covers antibody diversity within individuals. Isotypes are amino acid differences in antibodies found in different species, and allotypes are the differences found in individuals within the same species.

DIF: Easy REF: 16.3 OBJ: 16.3c Differentiate between the isotype, allotype, and idiotype of an antibody.

MSC: Understanding 6. Rebecca developed measles as a young child. As a teenager, she is reexposed to the measles virus during an outbreak at her high school. Explain the immune response that will most likely prevent Rebecca from experiencing any signs or symptoms of measles.

ANS: Exposure to the measles virus as a child would have triggered a primary response. During a primary response, activated B cells would proliferate and differentiate into both antibody-secreting plasma cells and memory B cells. The memory B cells would be primed to activate rapidly upon subsequent exposure to the same virus during the secondary immune response. IgG antibody production would be more rapid and the amount of IgG secreted would be much higher.

DIF: Moderate REF: 16.4 OBJ: 16.4a Explain the difference between primary and secondary antibody responses.

MSC: Applying 7. Explain how humans are able to produce millions of different antibodies when there are only about 1,000 genes or gene segments involved in antibody formation.

ANS: The genes involved in antibody formation are randomly rearranged in progenitor B cells. These rearrangements produce different antigen-binding sites. The antigen-binding site produced by gene rearrangement is then linked to a heavy chain. During this process, mutations are randomly introduced and different codons appear.

DIF: Moderate REF: 16.4 OBJ: 16.4c Summarize how the immune system generates vast antibody diversity.

MSC: Applying 8. Describe the process of affinity maturation.

ANS: Hypermutation of the DNA encoding the antigen-binding region of a memory B cell occurs. These random changes can alter the affinity of the antigen-binding site of the antibody produced. B cells capable of producing antibody with higher affinity are best able to bind to low levels of antigen and become activated. This process leads to memory B cells with higher affinity.

DIF: Moderate REF: 16.4 OBJ: 16.4d Describe the role of memory B cells during an antibody response.

MSC: Understanding 9. A two-month-old baby is found to lack class I MHC molecules. How would this defect impact an adaptive immune response?

ANS: Class I MHC molecules are found on the surface of all nucleated cells and are used to present intracellular antigen such as viral proteins to CD8 cytotoxic T cells. CD4 helper T cells and B cells would still be able to carry out antibody-mediated immunity because CD4 cells recognize MHC class II. Without MHC I, cytotoxic T cells would be unable to kill virus-infected and cancer cells.

DIF: Difficult REF: 16.5 OBJ: 16.5b Discuss the role of major histocompatibility proteins in the adaptive immune response.

MSC: Analyzing 10. Why is it important for T cells to weakly recognize self MHC proteins, and why is strong recognition problematic?

ANS:

T cells must be able to weakly recognize MHC proteins so the T-cell receptor can bind MHCassociated antigen. Without this binding, T cells would not be able to activate. Strong recognition is problematic because T cells would constantly react to normal self-cells without regard for the antigen bound.

DIF: Difficult REF: 16.5 OBJ: 16.5d Describe processes that minimize autoimmunity.

MSC: Analyzing

11. Describe the two-step molecular process required to activate TH0 cells.

ANS: TH0 cells with CD4 molecules are able to bind to antigen-MHC II complexes on the surface of antigenpresenting cells (APCs). After this initial binding, a CD28 molecule on the surface of the bound TH0 cell must bind to a B7 protein on the surface of the bound APC. DIF: Difficult REF: 16.6 OBJ: 16.6a Describe a T-cell receptor (TCR), and explain its role in T-cell activation.

MSC: Understanding 12. Explain the role of Class II MHC in B-cell activation.

ANS: Class II MHC is used by B cells to present antigen to activated helper T (TH) cells. Activated TH cells are able to bind to antigen-MHC II complexes on B cells. This antigen recognition and binding initiates heavy-chain class switching and differentiation in B cells during the later immune response.

DIF: Difficult REF: 16.6 OBJ: 16.6b Explain how a TCR also participates in B-cell activation.

MSC: Applying 13. Describe how infection by a virus such as hepatitis B causes tissue damage.

ANS: Intracellular pathogens such as viruses elicit a cellular immune response by cytotoxic T (TC) cells.

TC cells are able to recognize antigens from intracellular pathogens when they are presented bound to Class I MHC on antigen-presenting cells. Activated TC cells then travel throughout the body, bind to any cells presenting the same antigen, and destroy the cells. This cost of targeting the intracellular pathogens is destruction of body cells and therefore tissue damage.

DIF: Difficult REF: 16.7 OBJ: 16.7b Discuss how activated TC cells recognize their target host cells.

MSC: Applying 14. One way a pathogen may attempt to evade an immune response is by downregulating the production of Class I MHC molecules on infected cells. What type of pathogen would benefit from this adaptation and how would the pathogen benefit?

ANS: Viruses and other intracellular pathogens would benefit by downregulating MHC I on infected cells.

The role of MHC I is to present intracellular pathogens to cytotoxic T cells. Without MHC I to present antigen, cytotoxic T cells are unable to recognize and destroy infected cells. Natural killer cells should still attack cells that lack MHC I though.

DIF: Difficult

REF: 16.7

OBJ: 16.7e Diagram the basic ways that pathogens can avoid the immune system.

MSC: Applying 15. CASE HISTORY Nathan was a ten-month-old male who had suffered much in his short life. Since birth he had experienced recurrent serious extracellular bacterial infections, all of which were resolved by antibiotic treatment. On Christmas Day, Nathan’s mother discovered he had another high fever and a nonproductive cough (no mucus). He was also having trouble breathing. Fearing one more serious infection, Nathan’s mother rushed him to the hospital. An X-ray showed the lung infiltrate with the appearance of ground glass. A tube was placed through Nathan’s nose and into his lung, and a solution was used to wash out deep-lung contents for microscopic examination (bronchoalveolar lavage). The fluid yielded microscopic organisms. Nathan was hospitalized with pneumonia caused by Pneumocystis jirovecii, a yeastlike fungus. Although most of us have been infected with this organism, our immune systems almost always prevent disease. Finding the disease in Nathan suggested a serious immune dysfunction. An immunological workup revealed mild neutropenia (lower than normal numbers of neutrophils) but normal numbers of T and B cells, normal levels of complement, and normal complement activity. However, Nathan’s blood exhibited exceptionally high levels of IgM but very low IgG and IgA levels. The physician suspected a specific defect in Nathan’s T cells.

Explain how a T-cell deficit could lead to this anomaly in antibody production, a task normally completed by B cells. Could this still be the source of the problem if the doctor had discovered that only IgA was high, rather than IgM? ANS: Nathan’s B cells appear to be undergoing only T-independent activation, hence the production of primarily IgM. Because IgM can be produced without an activating T cell, this scenario fits; however, if it were only IgA, other causes should be investigated (possibly malignancies depending on students’ familiarity with that chapter).

DIF: Moderate REF: Case History 16.2 OBJ: 16.6d Explain why memory B cells do not always need T-cell help for activation.

MSC: Understanding 16. CASE HISTORY Luke, a 24-year-old mechanic from Egypt Beach, Massachusetts, was feeling run-down. Over the past month he had not been eating much and was always tired, and he recently noticed pain just under his right rib cage. His urine had recently turned the color of tea, and his wife noticed that the whites of his eyes were taking on a yellowish tinge. Luke finally went to the doctor, who suspected Luke had cirrhosis, a liver disease. This preliminary diagnosis was based on Luke’s symptoms. Luke’s abdominal pain was located over the liver, and the color of his urine and the jaundice evident in his eyes all pointed toward liver disease. Luke did not drink alcohol and had never left the country, but when questioned, Luke admitted to taking intravenous drugs. The doctor suspected hepatitis and ordered a series of blood tests to check for the presence of liver enzymes, antihepatitis antibodies, and hepatitis DNA or RNA in his blood. The tests revealed a high level of hepatitis B viral DNA. Luke had hepatitis B disease.

How can cellular immunity, which normally protects the body against known viral and other intracellular pathogens, be harmful to Luke, given his diagnosis? Consider how T cells recognize and respond to cells displaying foreign antigen.

ANS: Most cellular damage associated with hepatitis B is the direct result of the attack of cellular immune responses against infected liver cells. This tissue damage leads to the signs and symptoms associated with the disease.

DIF: Moderate REF: Case History 16.3 OBJ: 16.7b Discuss how activated TC cells recognize their target host cells.

MSC: Evaluating

Chapter 17: Vaccines, Diagnostics, and Immune Disorders LEARNING OBJECTIVES 17.1a Distinguish primary and secondary immunodeficiencies.

17.1b Describe the common forms of severe combined immunodeficiencies.

17.1c Compare the underlying defects and outcomes of bare lymphocyte syndrome, X-linked agammaglobulinemia, hyper IgM syndrome, selective IgA deficiency, and complement deficiencies.

17.2a Discuss the relationship between our immune system and cancer.

17.2b Distinguish lymphoma, leukemia, plasmocytoma, and multiple myeloma.

17.2c Explain the defects leading to B-cell neoplasms.

17.3a Explain what an allergen is.

17.3b Describe the development, pharmacology, and treatment of type I hypersensitivity.

17.3c Differentiate type II and type III hypersensitivities.

17.3d Discuss type IV hypersensitivity in terms of what cells are involved and how it can be used as a diagnostic tool.

17.4a Recall how the immune system differentiates self from nonself (foreign) antigens.

17.4b Discuss how autoreactive antibodies can be formed.

17.4c Describe the key features of the autoimmune diseases lupus, Graves’ disease, diabetes, rheumatoid arthritis, and myasthenia gravis.

17.4d Explain the basis of transplant rejection.

17.5a Describe how immunoprecipitation assays are used to measure immunoglobulin levels.

17.5b Explain agglutination and its use in blood typing and pathogen detection.

17.5c Distinguish direct, indirect, and sandwich enzyme-linked immunosorbent assays (ELISAs).

17.5d Discuss how monoclonal antibodies are made and their use in fluorescent antibody techniques (immunofluorescence microscopy, western blots, and flow cytometry).

17.6a Distinguish active from passive immunization.

17.6b List key features of an effective vaccine.

17.6c Explain the different types of vaccines.

17.6d Discuss the concept of herd immunity.

MULTIPLE CHOICE 1. An example of a secondary immunodeficiency would be a. DiGeorge syndrome. b. HIV. c. severe combined immunodeficiency syndrome. d. IgA deficiency.

ANS: B DIF: Moderate REF: 17.1 OBJ: 17.1a Distinguish primary and secondary immunodeficiencies.

MSC: Understanding 2. All of the following are consequences of bare lymphocyte syndrome (MHC II deficiency) EXCEPT a. the MHC II molecule is expressed on APCs. b. T cells will not form into TH1, TH2, or other types of helper T cells. c. cytotoxic T cells cannot be activated. d. B cells do not isotype switch.

ANS: A DIF: Difficult REF: 17.1 OBJ: 17.1b Describe the common forms of severe combined immunodeficiencies.

MSC: Analyzing 3. Which of the following is true regarding T-cell deficiencies? a. A mutation in the IL-2 receptor affects T-cell proliferation. b. A deficiency in ATP causes apoptosis in T, B, or NK cells. c. Antibodies produced are stable and never destroyed. d. Severe combined immunodeficiencies (SCIDs) are characterized by a lack of B cells.

ANS: A DIF: Moderate REF: 17.1 OBJ: 17.1b Describe the common forms of severe combined immunodeficiencies.

MSC: Understanding 4. All of the following are examples of B-cell disorders EXCEPT a. X-linked agammaglobulinemia (Burton’s disease). b. common variable immunodeficiency (CVID). c. DiGeorge syndrome. d. selective IgA deficiency.

ANS: C DIF: Moderate REF: 17.1 OBJ: 17.1c Compare the underlying defects and outcomes of bare lymphocyte syndrome, X-linked agammaglobulinemia, hyper IgM syndrome, selective IgA deficiency, and complement deficiencies.

MSC: Analyzing 5. Complement deficiencies are a. acquired during life. b. X-linked.

c. inherited autosomal traits. d. treated with antivirals.

ANS: C DIF: Easy REF: 17.1 OBJ: 17.1c Compare the underlying defects and outcomes of bare lymphocyte syndrome, X-linked agammaglobulinemia, hyper IgM syndrome, selective IgA deficiency, and complement deficiencies.

MSC: Remembering 6. How does immune surveillance against cancer work inside the host? a. Cancer cells are sought out but not destroyed. b. The immune system is suppressed. c. Immune cells are unable to recognize cancerous cells. d. Cancer cells are marked with surface antigens not present on normal cells.

ANS: D DIF: Moderate REF: 17.2 OBJ: 17.2a Discuss the relationship between our immune system and cancer.

MSC: Applying 7. Patients with primary immunodeficiencies and who are immunosuppressed are prone to developing cancers. Which is the most commonly developed cancer for these patients? a. Epstein-Barr c. myelomas b. B-cell lymphomas d. mononucleosis ANS: B DIF: Difficult REF: 17.2 OBJ: 17.2a Discuss the relationship between our immune system and cancer.

MSC: Applying 8. Leukemia refers to a. a malignant lymphoid cell found in circulation or bone marrow.

b. a solid mass in a lymphoid organ. c. growth of a plasma cell. d. cancerous plasma cells that appear at multiple sites.

ANS: A DIF: Easy REF: 17.2 OBJ: 17.2b Distinguish lymphoma, leukemia, plasmacytoma, and multiple myeloma.

MSC: Remembering 9. All of the following are true about Hodgkin’s lymphoma EXCEPT that a. it is often caused by the herpes simplex virus. b. symptoms include fever, night sweats, and weight loss. c. tumors contain neoplastic, multinucleated Reed-Sternberg cells. d. the release of cytokines such as TNF-alpha contributes to the fever and chronic inflammation.

ANS: A DIF: Difficult REF: 17.2 OBJ: 17.2c Explain the defects leading to B-cell neoplasms.

MSC: Analyzing

10. All of the following are true about B-cell neoplasms EXCEPT that a. cancers arise in B cells when genes that control cell division are dysregulated and fail to replicate. b. follicular lymphoma occurs when the bcl-2 gene is activated and prevents apoptosis. c. chronic lymphocytic leukemia occurs when there is a deletion in chromosome 13. d. Burkitt’s lymphoma develops when the c-myo gene moves next to expressed antibody genes.

ANS: A DIF: Difficult REF: 17.2 OBJ: 17.2c Explain the defects leading to B-cell neoplasms.

MSC: Analyzing

11. All of the following are examples of antibody-mediated hypersensitivities EXCEPT ________ hypersensitivity. a. IgE-mediated c. immune complex–mediated b. antibody-mediated cytotoxic d. cell-mediated ANS: D DIF: Moderate REF: 17.3 OBJ: 17.3c Differentiate type II and type III hypersensitivities. MSC: Understanding 12. Which of the following is a symptom of systemic anaphylaxis? a. sneezing c. rhinitis b. watery, itchy eyes d. edema ANS: D DIF: Moderate REF: 17.3 OBJ: 17.3b Describe the development, pharmacology, and treatment of type I hypersensitivity.

MSC: Understanding 13. Anaphylaxis is the term for reactions caused when certain antigens combine with a. IgE antibodies. c. IgG antibodies. b. macrophages. d. histamine.

ANS: A DIF: Easy REF: 17.3 OBJ: 17.3b Describe the development, pharmacology, and treatment of type I hypersensitivity.

MSC: Remembering 14. Epinephrine is used to reverse anaphylaxis. This is achieved by all of the following EXCEPT a. stimulating adenylate cyclase activity. b. decreasing cAMP levels.

c. relaxing smooth muscle. d. preventing degranulation of the mast cell.

ANS: B DIF: Difficult REF: 17.3 OBJ: 17.3b Describe the development, pharmacology, and treatment of type I hypersensitivity.

MSC: Understanding 15. Type II hypersensitivities differ from type III sensitivities in that only type II involves a. surface antigens. c. antibodies. b. soluble antigens. d. histamine.

ANS: A DIF: Moderate REF: 17.3 OBJ: 17.3c Differentiate type II and type III hypersensitivities. MSC: Understanding 16. Which of the following blood transfusions would be compatible? a. c. b. d.

ANS: D DIF: Moderate REF: 17.3 OBJ: 17.3c Differentiate type II and type III hypersensitivities. MSC: Applying 17. Symptoms of an immune complex reaction are due to a. destruction of the antigen. c. phagocytosis. b. complement activation. d. cytokines.

ANS: B DIF: Moderate REF: 17.3 OBJ: 17.3c Differentiate type II and type III hypersensitivities. MSC: Understanding 18. What is the end result of the immune complex reaction demonstrated in the figure below?

a. b. c. d.

IgG is directed against cell membrane antigens.

Complement is activated.

Neutrophils are attracted and release enzymes.

Endothelial cells are damaged.

ANS: D DIF: Moderate REF: 17.3 OBJ: 17.3c Differentiate type II and type III hypersensitivities. MSC: Applying 19. Allergic contact dermatitis is due to a. sensitized T cells. b. IgE antibodies.

c. IgG antibodies. d. IgM antibodies.

ANS: A DIF: Easy REF: 17.3 OBJ: 17.3d Discuss type IV hypersensitivity in terms of what cells are involved and how it can be used as a diagnostic tool.

MSC: Understanding 20. An autoimmune response is generated within the host when a. immune tolerance against self is lost. b. immune cells attack foreign antigens. c. NK cells bind host tissue. d. T cells deactivate self-reacting B cells.

ANS: A DIF: Easy REF: 17.4 OBJ: 17.4a Recall how the immune system differentiates self from nonself (foreign) antigens.

MSC: Remembering 21. All of the following are true of the generation of autoreactive antibodies EXCEPT a. B cells escape the negative selection process. b. self-reacting B cells can be activated without specific T-cell assistance. c. some microbial antigens can also trigger autoimmune reactions. d. self-reacting B cells do not take up and process self-antigens.

ANS: D DIF: Difficult REF: 17.4 OBJ: 17.4b Discuss how autoreactive antibodies can be formed.

MSC: Analyzing 22. All of the following are examples of autoimmune diseases EXCEPT a. lupus. c. Graves’ disease. b. Lyme disease. d. type-1 diabetes.

ANS: B DIF: Easy REF: 17.4 OBJ: 17.4c Describe the key features of the autoimmune diseases lupus, Graves’ disease, diabetes, rheumatoid arthritis, and myasthenia gravis.

MSC: Remembering 23. Graves’ disease and Hashimoto’s disease are different in the fact that Graves’ disease a. targets the thyroid. c. causes hyperthyroidism. b. involves autoantibodies. d. causes hypothyroidism.

ANS: C DIF: Easy REF: 17.4 OBJ: 17.4c Describe the key features of the autoimmune diseases lupus, Graves’ disease, diabetes, rheumatoid arthritis, and myasthenia gravis.

MSC: Remembering 24. Which of the following is the major player in transplant rejection? a. MHC proteins of the donor c. MHC proteins of the host b. T helper cells of the donor d. T helper cells of the host ANS: A DIF: Moderate REF: 17.4 OBJ: 17.4d Explain the basis of transplant rejection.

MSC: Understanding

25. Sensitivity differs from specificity in that sensitivity a. measures how selective an antibody is. b. occurs when antibodies bind dissimilar antigens. c. reflects how few antigen or antibody molecules a test can detect. d. is not important when conducting a serological test.

ANS: C DIF: Moderate REF: 17.5 OBJ: 17.5a Describe how immunoprecipitation assays are used to measure immunoglobulin levels.

MSC: Understanding

26. All of the following pertain to serology EXCEPT a. detecting antibodies. c. diagnosing various diseases. b. detecting antigens. d. revealing the contents of serum.

ANS: B DIF: Moderate REF: 17.5 OBJ: 17.5a Describe how immunoprecipitation assays are used to measure immunoglobulin levels.

MSC: Applying 27. All of the following regarding immunoprecipitation are correct EXCEPT a. it is observed both in vitro and in vivo. b. too many antigens cause the test not to work. c. too many antibody molecules cause the test not to work. d. equivalence is the point at which there are roughly the same number of antigenic and antigen-binding sites.

ANS: A DIF: Moderate REF: 17.5 OBJ: 17.5a Describe how immunoprecipitation assays are used to measure immunoglobulin levels.

MSC: Analyzing 28. The image below is of a radial immunodiffusion assay embedded with anti-IgA antibodies. Which sample has the highest concentration of IgA antibodies?

a. A b. B

c. C d. D

ANS: A DIF: Easy REF: 17.5 OBJ: 17.5a Describe how immunoprecipitation assays are used to measure immunoglobulin levels.

MSC: Applying 29. Which of the following is a test to determine a patient’s blood type by mixing the patient’s red blood cells with antibodies? a. agglutination reaction b. immunoprecipitation c. enzyme-linked immunosorbent assay (ELISA) d. immunofluorescence ANS: A DIF: Easy REF: 17.5 OBJ: 17.5b Explain agglutination and its use in blood typing and pathogen detection.

MSC: Analyzing 30. The figure below illustrates a sandwich ELISA. What is happening in step 3?

a. b. c. d.

Enzyme-linked detection antibody is added.

Secondary antibody is added and binds to antigens.

The plate is coated with capture antibodies.

Serum sample is added.

ANS: B DIF: Moderate REF: 17.5 OBJ: 17.5c Distinguish direct, indirect, and sandwich enzyme-linked immunosorbent assays (ELISAs).

MSC: Applying 31. Refer to the image below. Which component came from the patient in this sandwich ELISA?

a. A b. B

c. C d. D

ANS: A DIF: Moderate REF: 17.5 OBJ: 17.5c Distinguish direct, indirect, and sandwich enzyme-linked immunosorbent assays (ELISAs).

MSC: Applying 32. Which item is from the patient in a direct ELISA test? a. antigen c. antibodies against the antigen

b. substrate for the enzyme

d. antihuman immune serum

ANS: A DIF: Moderate REF: 17.5 OBJ: 17.5c Distinguish direct, indirect, and sandwich enzyme-linked immunosorbent assays (ELISAs).

MSC: Understanding 33. Which of the following does NOT use fluorescent-labeled antibodies? a. agglutination c. immunofluorescence microscopy b. western blot d. flow cytometry ANS: A DIF: Easy REF: 17.5 OBJ: 17.5c Distinguish direct, indirect, and sandwich enzyme-linked immunosorbent assays (ELISAs).

MSC: Remembering 34. All of the following are examples of passive immunization EXCEPT a. injection of immune globulin. c. antitoxins. b. breast-feeding. d. vaccinia virus.

ANS: D DIF: Easy REF: 17.6 OBJ: 17.6a Distinguish active from passive immunization.

MSC: Understanding

35. Determine the FALSE statement below. An effective vaccine a. will deactivate B and T cells. b. will generate memory. c. should not require many boosters. d. must protect against the natural pathogen.

ANS: A DIF: Moderate REF: 17.6 OBJ: 17.6b List key features of an effective vaccine.

36. A hybridoma results from the fusion of a(n) a. B cell with a T cell. b. B cell with a myeloma cell.

MSC: Understanding

c. antigen with an antibody. d. antigen with a B cell.

ANS: B DIF: Easy REF: 17.5 OBJ: 17.5c Distinguish direct, indirect, and sandwich enzyme-linked immunosorbent assays (ELISAs).

MSC: Remembering 37. What type of vaccine is the live, weakened measles virus? a. conjugated c. DNA b. subunit d. attenuated whole-agent ANS: D DIF: Easy REF: 17.6 OBJ: 17.6c Explain the different types of vaccines.

MSC: Understanding

38. All of the following are generally used in vaccines EXCEPT a. toxoids. c. antibodies. b. parts of bacterial cells. d. inactivated viruses.

ANS: C DIF: Easy REF: 17.6 OBJ: 17.6c Explain the different types of vaccines.

MSC: Understanding

39. A plasmid-encoding protein antigen from West Nile virus is injected into muscle cells. This is an example of a(n) a. DNA vaccine. c. subunit vaccine. b. attenuated vaccine. d. toxoid.

ANS: A DIF: Easy REF: 17.6 OBJ: 17.6c Explain the different types of vaccines.

MSC: Analyzing

40. The following are all true about herd immunity EXCEPT that it a. only works for diseases that are contagious. b. occurs when a large portion of a population is immunized. c. is possible for noncontagious infections like tetanus. d. protects unimmunized individuals.

ANS: C DIF: Moderate REF: 17.6 OBJ: 17.6d Discuss the concept of herd immunity.

MSC: Analyzing

41. CASE HISTORY The patient, Asuncion, is an eight-year-old girl from Argentina. She received the BCG vaccine for tuberculosis about one year before coming to the United States. Upon entering school in the United States, she must take a skin test for tuberculosis (TB). Asuncion tries to refuse but is told it is a requirement. She allows the nurse to apply the test to her arm. Three days later, the test site has a large red lesion and the skin is starting to slough (peel off).

The reaction Asuncion is experiencing is most similar to someone who has a. been exposed to poison ivy and now has contact dermatitis. b. type A blood, but has been given a type B transfusion. c. an urticarial rash in response to penicillin treatment. d. an allergic reaction to bee venom injected during a sting.

ANS: A DIF: Easy REF: Case History 17.4 OBJ: 17.3c Differentiate type II and type III hypersensitivities. MSC: Applying COMPLETION 1. Patients with ________ have normal or elevated serum IgM levels but low levels of other antibodies.

ANS: hyper IgM syndrome DIF: Easy REF: 17.1 OBJ: 17.1c Compare the underlying defects and outcomes of bare lymphocyte syndrome, X-linked agammaglobulinemia, hyper IgM syndrome, selective IgA deficiency, and complement deficiencies.

MSC: Remembering 2. The process that detects and eliminates cancer cells as they arise is called a(n) ________.

ANS: immune surveillance DIF: Easy REF: 17.2 OBJ: 17.2a Discuss the relationship between our immune system and cancer.

MSC: Remembering 3. Antigens that possess structures similar in shape to host structures are called ________.

ANS: allergens DIF: Easy REF: 17.3 MSC: Remembering

OBJ: 17.3a Explain what an allergen is.

4. In the immune complex reaction shown in the figure below, the structure labeled as “A” is called a(n) ________.

ANS: antibody DIF: Easy REF: 17.3 OBJ: 17.3c Differentiate type II and type III hypersensitivities. MSC: Applying 5. Injecting an antigen such as a weakened or killed pathogen is called ________ immunization, while ________ immunization is a type of immunotherapy.

ANS: active; passive DIF: Easy REF: 17.6 OBJ: 17.6a Distinguish active from passive immunization.

MSC: Remembering

SHORT ANSWER 1. Draw and label the key mediators of a type 1 hypersensitivity. Be sure to indicate where medical intervention can take place.

ANS: Students should be able to draw a figure similar to the one highlighted in Figure 17.6.

First, an allergy-prone person must encounter the allergen and have it bind to B-cell receptors. Once this is done, the B cell will produce large amounts of IgE antibodies specific to the allergen. These IgE antibodies bind circulating mast cells. Upon subsequent exposures, the allergen will bind the antibodies bound to the mast cells and cause a degranulation. When the mast cell undergoes degranulation, it will release chemical mediators such as histamine, prostaglandins, and leukotrienes, which manifest the symptoms of allergies. One place for medical intervention would be the administration of epinephrine. Epinephrine acts on host mast cells and prevents degranulation of the mast cell.

DIF: Difficult REF: 17.3 OBJ: 17.3b Describe the development, pharmacology, and treatment of type I hypersensitivity.

MSC: Evaluating 2. Describe an ELISA test to detect the presence of hepatitis in a patient’s blood sample.

ANS: The microtiter plate would first be coated with an antihepatitis capture antibody. The serum harvested from the patient’s blood sample is then added to the assay. Any hepatitis antigen present in the serum will bind to the capture antibody on the bottom of the plate. Next a secondary antibody is added and will bind to the hepatitis antigen. The secondary antibody will then be bound by an enzyme-linked detection antibody. Finally, substrate is added and the enzyme converts the substrate to a colored form.

DIF: Difficult REF: 17.5 OBJ: 17.5c Distinguish direct, indirect, and sandwich enzyme-linked immunosorbent assays (ELISAs).

MSC: Applying 3. Using the figure below, please describe the steps taken to produce monoclonal antibodies and explain why they are used in diagnostic tests and disease treatments.

ANS: Mice or rabbits are injected with a primary dose of antigen and subsequently boosted later. B cells are then removed from the animals’ spleens, sorted into wells of a microtiter plate, and stimulated to make antibody. Antibodies from each well can be screened for specificity against the desired epitope. The desired B cells are then fused with myeloma cancer cells that divide indefinitely. The resulting immortalized cells are called a hybridoma and will continually produce one type of antibody specific to only one epitope.

Monoclonal antibodies are used in diagnostic tests to detect antibodies or antigens, treat viral disease, classify strains of bacterial species, and identify cells or molecules in an organism. They are useful in these techniques because they are highly specific to only one epitope on antigens.

DIF: Difficult REF: 17.5 OBJ: 17.5c Distinguish direct, indirect, and sandwich enzyme-linked immunosorbent assays (ELISAs).

MSC: Applying 4. Describe what is happening in figures A and B below. Explain the concept of herd immunity and how it protects the unvaccinated population.

ANS: Figure A displays a scenario where there are two sick individuals among a population of unvaccinated people. This allows the disease-causing agent to spread freely through the population, infecting most of the individuals. Figure B displays a scenario where most of the population is immunized. By vaccinating a large fraction of the population, the spread of the disease is contained.

Herd immunity occurs when a large portion of the population is immunized. Because the vaccinated individuals in the “herd” or community will not become infected, they cannot spread the disease to others. It is estimated that immunizing 75% or more of the population can reduce the incidence of the disease by cutting transmission.

DIF: Difficult MSC: Applying

REF: 17.6

OBJ: 17.6d Discuss the concept of herd immunity.

5. Using the figure below, please describe in detail how this type IV sensitivity is produced and how tissue is ultimately damaged.

ANS: Type IV hypersensitivities are triggered by antigen-specific T cells. There are two stages in the development of type IV hypersensitivities. The first stage is sensitization and involves processing and presentation of antigen on dendritic cells. When exposure occurs, dendritic cells process the antigen and display them to T cells. The T cells make and secrete cytokines that call in macrophages and PMNs from circulation. Upon secondary exposure to the same antigen, memory T cells that were created activate quickly and release pro-inflammatory cytokines and attract cells of the immune system, which will destroy host cells.

DIF: Difficult REF: 17.3 OBJ: 17.3d Discuss type IV hypersensitivity in terms of what cells are involved and how it can be used as a diagnostic tool.

MSC: Applying 6. CASE HISTORY The patient, Asuncion, is an eight-year-old girl from Argentina. She received the BCG vaccine for tuberculosis about one year before coming to the United States. Upon entering school in the United States, she must take a skin test for tuberculosis (TB). Asuncion tries to refuse but is told it is a requirement. She allows the nurse to apply the test to her arm. Three days later, the test site has a large red lesion and the skin is starting to slough (peel off).

From the information given in the case study, it is unclear whether Asuncion could potentially pose a TB infection risk to her classmates. Why was this test an inappropriate one for Asuncion and what would be a more useful alternative?

ANS: The test examines immune response to TB proteins that are also present in the vaccine; thus we would predict a positive response with or without infection. A chest X-ray can be used to distinguish cases of active TB. DIF: Moderate REF: Case History 17.4 OBJ: 17.3d Discuss type IV hypersensitivity in terms of what cells are involved and how it can be used as a diagnostic tool.

MSC: Analyzing 7. CASE HISTORY

Richard, who is blood group B, was undergoing surgery after a car accident and accidentally received a transfusion with type A blood. Within hours, Richard experienced chills and lowered blood pressure.

His urine turned red with blood. All these symptoms indicate an ABO blood group incompatibility.

Is there an identifiable allergen present in this case study? How can you tell?

ANS: There is an allergen—the type A antigen associated with the foreign blood cell. The definition of antigen is much broader than that used by most laypersons to refer to the particular antigens that cause type I hypersensitivities.

DIF: Easy REF: Case History 17.3 OBJ: 17.3a Explain what an allergen is. MSC: Applying

Chapter 18: Microbial Pathogenesis LEARNING OBJECTIVES 18.1a Differentiate between pathogenicity genes and pathogenicity islands.

18.1b Correlate horizontal gene transfer with pathogen evolution.

18.2a Explain why pathogens need to attach to host cells.

18.2b Describe various microbial attachment techniques.

18.2c Differentiate the structure and function of type I and type IV pili.

18.2d Discuss the role of biofilms in pathogenicity.

18.3a Describe the nine basic cellular targets for bacterial toxins.

18.3b Explain the modes of action for staphylococcal alpha toxin, cholera toxin, diphtheria toxin, Shiga toxin, and anthrax toxin.

18.3c Differentiate endotoxin from exotoxin.

18.4a Differentiate type II, type III, and type IV secretion systems used to export exotoxins/effector proteins.

18.4b Discuss the evolutionary relationships between secretion systems and other microbial structures.

18.5a Distinguish extracellular pathogens from facultative and obligate intracellular pathogens.

18.5b Discuss the three main ways intracellular pathogens avoid intracellular destruction.

18.5c Describe various strategies pathogens use to avoid the immune system.

18.5d Explain why and how intracellular pathogens distinguish between intracellular and extracellular existence.

18.6a Discuss antigenic variation in rhinovirus and influenza viruses.

18.6b Explain how human immunodeficiency virus (HIV) targets T cells and describe the roles of Nef and Tat proteins in HIV pathogenesis.

18.6c Outline how human papillomavirus (HPV) causes unregulated cell division.

18.6d Explain latency of herpes virus and the role of microRNAs in helping the virus reactivate.

18.7a Describe different ways protozoans invade host cells.

18.7b Correlate the immune response to protozoan-induced damage to host tissues.

18.7c Explain several mechanisms protozoans use to avoid the immune system.

MULTIPLE CHOICE 1. Genomic islands have all of the following features EXCEPT a. they are flanked by phage or plasmid genes. b. the ratio of GC/AT nucleases. c. they do not need toxins or secretion systems. d. they encode clusters of genes that contribute to the fitness of the organism.

ANS: C DIF: Moderate REF: 18.1 OBJ: 18.1a Differentiate between pathogenicity genes and pathogenicity islands.

MSC: Analyzing 2. Which statement about horizontal gene transfer is correct? a. Few pathogenicity islands are generated by horizontal transmission. b. Horizontal gene transfers move whole blocks of DNA from one organism to another. c. Horizontal gene transfer helps pathogens evolve. d. All genes code for toxins.

ANS: B DIF: Difficult REF: 18.1 OBJ: 18.1b Correlate horizontal gene transfer with pathogen evolution.

MSC: Analyzing 3. All of the following are methods of microbial attachment EXCEPT a. capsids. c. fimbriae. b. pili. d. type IV secretion systems.

ANS: D DIF: Easy REF: 18.2 OBJ: 18.2b Describe various microbial attachment techniques.

4. The fimbria of E. coli is an example of a(n) a. adhesion. b. receptor.

MSC: Remembering

c. endotoxin. d. exotoxin.

ANS: A DIF: Easy REF: 18.2 OBJ: 18.2b Describe various microbial attachment techniques.

MSC: Understanding

5. Type I pili are different from type IV pili in that type I pili a. are static structures. c. allow for twitching motility. b. are thin and flexible. d. are dynamic.

ANS: A DIF: Moderate REF: 18.2 OBJ: 18.2c Differentiate the structure and function of type I and type IV pili.

MSC: Understanding 6. Interfering with microbial attachment a. makes a pathogenic organism less virulent. b. disrupts toxin production. c. increases formation of microbial biofilms. d. increases virulence.

ANS: A DIF: Difficult REF: 18.2 OBJ: 18.2c Differentiate the structure and function of type I and type IV pili.

MSC: Analyzing 7. Biofilm infections are important clinically because a. WBC easily penetrate biofilms. b. bacteria in biofilms are more susceptible to antimicrobial compounds. c. bacteria in biofilms can persist against host defenses. d. bacteria in biofilms do not grow on medical devices.

ANS: C DIF: Moderate REF: 18.2 OBJ: 18.2d Discuss the role of biofilms in pathogenicity.

8. All of the following are exotoxins EXCEPT a. superantigens. b. AB toxins.

MSC: Understanding

c. plasma membrane disruption toxins. d. lipopolysaccharides.

ANS: D DIF: Easy REF: 18.3 OBJ: 18.3a Describe the nine basic cellular targets for bacterial toxins.

MSC: Remembering 9. All of the following are targets for bacterial toxins EXCEPT a. signal transduction. c. DNA synthesis.

b. host membranes.

d. protein synthesis.

ANS: C DIF: Moderate REF: 18.3 OBJ: 18.3a Describe the nine basic cellular targets for bacterial toxins.

MSC: Understanding 10. Which of the following statements is FALSE? a. Hemolysins lyse red blood cells. b. Leukocidins destroy neutrophils. c. AB toxins interfere with protein synthesis. d. Protease exotoxins build proteins.

ANS: D DIF: Moderate REF: 18.3 OBJ: 18.3a Describe the nine basic cellular targets for bacterial toxins.

MSC: Applying 11. Alpha toxin secreted by Staphylococcus aureus is a a. hyaluronidase. c. kinase. b. leucocidin. d. hemolysin.

ANS: D DIF: Easy REF: 18.3 OBJ: 18.3b Explain the modes of action for staphylococcal alpha toxin, cholera toxin, diphtheria toxin, Shiga toxin, and anthrax toxin.

MSC: Remembering 12. All of the following are true about cholera toxin EXCEPT that it a. is an endotoxin. b. is an AB toxin. c. reverses the absorption process in the intestines. d. causes severe diarrhea.

ANS: A DIF: Moderate REF: 18.3 OBJ: 18.3b Explain the modes of action for staphylococcal alpha toxin, cholera toxin, diphtheria toxin, Shiga toxin, and anthrax toxin.

MSC: Understanding 13. Endotoxins are a. associated with Gram-positive bacteria. b. molecules that bind nerve cells. c. part of the Gram-negative cell wall. d. excreted from the cell.

ANS: C DIF: Easy REF: 18.3 OBJ: 18.3c Differentiate endotoxin from exotoxin.

MSC: Understanding

14. A type __________ protein secretion system is NOT an example of a bacterial secretion system that is paralogous to another molecular machine. a. I c. III b. II d. IV ANS: A DIF: Moderate REF: 18.4 OBJ: 18.4b Discuss the evolutionary relationships between secretion systems and other microbial structures.

MSC: Remembering 15. Which of the following is true regarding type II secretion systems? a. The type II secretion genes are homologous to the type IV pilus. b. Type II secretion mechanisms are static with no twitching motility. c. Proteins secreted by type II secretion systems are secreted directly out of the cell.

d. Shiga toxin is a well-known example of a protein that a type II secretion mechanism expels.

ANS: A DIF: Difficult REF: 18.4 OBJ: 18.4a Differentiate type II, type III, and type IV secretion systems used to export exotoxins/effector proteins.

MSC: Analyzing 16. All of the following statements about type III secretion systems are true EXCEPT a. proteins are injected directly into the eukaryotic cells. b. type III secretion systems are evolutionarily related to flagellar genes. c. cell-to-cell contact triggers type III secretion systems. d. virulence proteins secreted by type III systems alter protein synthesis.

ANS: D DIF: Moderate REF: 18.4 OBJ: 18.4a Differentiate type II, type III, and type IV secretion systems used to export exotoxins/effector proteins.

MSC: Analyzing 17. Refer to the figure below. The secretion system displayed mirrors that of a pilus. Which secretion system is this?

a. type I b. type II

c. type III d. type IV

ANS: B DIF: Moderate REF: 18.4 OBJ: 18.4a Differentiate type II, type III, and type IV secretion systems used to export exotoxins/effector proteins.

MSC: Applying 18. Rickettsia will not grow outside a living eukaryotic cell. What type of organism is this? a. extracellular pathogen c. intracellular pathogen b. facultative intracellular pathogen d. obligate extracellular pathogen ANS: C DIF: Moderate REF: 18.5 OBJ: 18.5a Distinguish extracellular pathogens from facultative and obligate intracellular pathogens.

MSC: Understanding 19. All of the following are ways bacteria evade phagocytic digestion and survive intracellularly EXCEPT

a. b. c. d.

escaping the phagosome. toxin production within the phagosome. inhibiting lysosome-phagosome fusion. survival within the phagolysosome.

ANS: B DIF: Moderate REF: 18.5 OBJ: 18.5b Discuss the three main ways intracellular pathogens avoid intracellular destruction.

MSC: Understanding 20. Shiga toxin polypeptide B binds to surface gangliosides on target cells. If the gangliosides were removed, a. polypeptide A would bind to target cells. b. polypeptide A would enter the cells. c. polypeptide B would not be able to bind. d. Vibrio would not produce cholera toxin.

ANS: C DIF: Moderate REF: 18.3 OBJ: 18.3b Explain the modes of action for staphylococcal alpha toxin, cholera toxin, diphtheria toxin, Shiga toxin, and anthrax toxin.

MSC: Applying 21. Organisms such as Shigella and Listeria are able to move from cell to cell without being detected by the host immune system. They do this through the production of a. an actin tail that propels them from cell to cell. b. a capsule to avoid antibody binding. c. protein A molecules to bind the Fc region of antibodies. d. proteins to trigger apoptosis in host cells.

ANS: A DIF: Moderate REF: 18.5 OBJ: 18.5c Describe various strategies pathogens use to avoid the immune system.

MSC: Applying 22. All of the following are ways pathogens avoid destruction by the host immune system EXCEPT a. capsules. c. antigenic variations. b. triggering apoptosis. d. toxin production.

ANS: D DIF: Easy REF: 18.5 OBJ: 18.5d Explain why and how intracellular pathogens distinguish between intracellular and extracellular existence.

MSC: Remembering 23. In viruses such as influenza, the ability to undergo a major genetic alteration is called antigenic a. drift. c. variation. b. shift. d. binding.

ANS: B DIF: Easy REF: 18.6 OBJ: 18.6a Discuss antigenic variation in rhinovirus and influenza viruses.

MSC: Remembering 24. Antigenic drift occurs when a. two viruses infect the same cell. b. a new viral strain is produced. c. random mutations occur in the neuraminidase spike. d. random mutations occur in the hemagglutinin spike.

ANS: D DIF: Moderate REF: 18.6 OBJ: 18.6a Discuss antigenic variation in rhinovirus and influenza viruses.

MSC: Understanding

25. The human immunodeficiency virus (HIV) primarily targets which subset of immune cells? a. CD8+ T cells c. macrophages b. CD4+ T cells d. dendritic cells ANS: B DIF: Easy REF: 18.6 OBJ: 18.6b Explain how human immunodeficiency virus (HIV) targets T cells and describe the roles of Nef and Tat proteins in HIV pathogenesis.

MSC: Remembering 26. All of the following statements are true about HIV EXCEPT a. HIV produces a Nef protein, which prevents T-cell apoptosis. b. Tat increases MHC I synthesis on host cells. c. Nef protein inhibits a regulatory cascade that leads to apoptosis. d. Tat stimulates apoptosis in infected host cells.

ANS: C DIF: Difficult REF: 18.6 OBJ: 18.6b Explain how human immunodeficiency virus (HIV) targets T cells and describe the roles of Nef and Tat proteins in HIV pathogenesis.

MSC: Analyzing 27. Cervical warts are caused by a. HBV. b. HPV.

c. HIV. d. herpes.

ANS: B DIF: Easy REF: 18.6 OBJ: 18.6c Outline how human papillomavirus (HPV) causes unregulated cell division.

MSC: Remembering 28. Which of the following is true regarding the herpes virus? a. It is the etiological agent of cervical warts. b. The virus cannot enter into a latent state in neural ganglia. c. Latent herpes virus DNA produces microRNAs that interfere with apoptosis. d. Herpes viruses are double-stranded RNA viruses.

ANS: C DIF: Moderate REF: 18.6 OBJ: 18.6d Explain latency of herpes virus and the role of microRNAs in helping the virus reactivate.

MSC: Analyzing 29. Damage from protozoan infections is due mainly to the a. toxins that are released. b. ability of the organism to persist within host tissue. c. ability of the organism to turn on the host immune system. d. cell wall components of the pathogen.

ANS: B DIF: Moderate REF: 18.7 OBJ: 18.7b Correlate the immune response to protozoan-induced damage to host tissues.

MSC: Understanding 30. The structure labeled as “A” in the figure below is called a(n)

a. protease. b. MIC protein.

c. nucleus. d. actin-myosin motor.

ANS: A DIF: Easy REF: 18.7 OBJ: 18.7a Describe different ways protozoans invade host cells.

MSC: Applying 31. In the image below, the pathogen uses the actin-myosin motor

a. to enter the host cell. b. produce toxins.

c. as a secretion apparatus. d. to prevent phagocytosis.

ANS: A DIF: Easy REF: 18.7 OBJ: 18.7a Describe different ways protozoans invade host cells.

MSC: Applying 32. Protozoans use all the following mechanisms to avoid the host immune system EXCEPT a. antigenic variation. c. antigenic masking. b. toxin production. d. intracellular location.

ANS: B DIF: Easy REF: 18.7 OBJ: 18.7c Explain several mechanisms protozoans use to avoid the immune system.

MSC: Remembering 33. Which of the following protozoans uses antigenic variation to circumvent the host immune system? a. plasmodium c. leishmania b. entamoeba d. trypanosome ANS: D DIF: Moderate REF: 18.7 OBJ: 18.7c Explain several mechanisms protozoans use to avoid the immune system.

MSC: Remembering 34. All of the following are required for disease to occur. What is the second step in microbial pathogenesis? a. pathogen exit c. pathogen entry b. host damage d. tissue attachment ANS: D DIF: Easy REF: 18.2 OBJ: 18.2a Explain why pathogens need to attach to host cells.

MSC: Understanding 35. Which of the following is an example of an obligate intracellular pathogen? a. Listeria monocytogenes c. Coxiella burnetii b. Shigella dysenteriae d. Streptococcus pneumoniae ANS: C DIF: Moderate REF: 18.5 OBJ: 18.5a Distinguish extracellular pathogens from facultative and obligate intracellular pathogens.

MSC: Understanding 36. Once a bacterium attaches to and enters a host cell within a phagosome, the pathogen has one of three fates, depending on the pathogen. According to the figure below, Shigella and Listeria __________ to avoid being destroyed by the host cell.

a. survive inside the phagosome b. escape from the phagosome

c. prevent phagosome-lysosome fusion d. induce apoptosis

ANS: B DIF: Moderate REF: 18.5 OBJ: 18.5b Discuss the three main ways intracellular pathogens avoid intracellular destruction.

MSC: Applying 37. According to the figure below, which of the following is true about Coxiella?

a. b. c. d.

Coxiella prevents phagocytosis.

Coxiella prevents phagosome-lysosome fusion.

Once inside the phagosome, Coxiella interferes with cell-signaling pathways.

It escapes the phagosome before lysosomal fusion.

ANS: B DIF: Moderate REF: 18.5 OBJ: 18.5b Discuss the three main ways intracellular pathogens avoid intracellular destruction.

MSC: Applying 38. All of the following are true about bacterial capsules EXCEPT a. they are produced by intracellular pathogens to avoid the host immune system. b. they coat bacterial cell wall components inhibiting phagocytosis. c. the slippery nature of capsules make “grabbing” the bacterial cell difficult. d. the immune system attacks encapsulated organisms with opsonizing antibodies.

ANS: A DIF: Moderate REF: 18.5 OBJ: 18.5c Describe various strategies pathogens use to avoid the immune system.

MSC: Analyzing 39. The purpose of the Tat protein in an HIV infection is to a. downregulate CD4 and MHC class I expression. b. inhibit virus assembly. c. accelerate HIV transcription by the host cell. d. protect the cell from being killed by CD8 cytotoxic cells.

ANS: C DIF: Moderate REF: 18.6 OBJ: 18.6b Explain how human immunodeficiency virus (HIV) targets T cells and describe the roles of Nef and Tat proteins in HIV pathogenesis.

MSC: Analyzing 40. CASE HISTORY

Will, a formerly rambunctious five-year-old from San Francisco, was taken to the emergency department after having a severe cough for two weeks. His illness started as a runny nose, dry cough, and low-grade fever. But within days the coughing would come in violent fits lasting up to one minute (called a paroxysm). The nurse practitioner attending Will observed one of these fits. Unable to breathe between coughs, the boy became cyanotic (turned blue). When the staccato of coughs finally ended, Will gasped, desperate for breath. The air rushing to fill his lungs made an ear-piercing whooping sound. This telltale “whoop” led the nurse practitioner to suspect whooping cough, a disease highly contagious in its early stages. In the later stages (greater than four weeks) the patient is no longer contagious because the bacterial agent, Bordetella pertussis, has succumbed to the immune response. However, the telltale cough will persist for weeks while the lungs repair the damage caused by the pertussis toxins. The nurse practitioner, now wearing a mask, took a nasopharyngeal swab sample for bacteriological culture and prescribed the antibiotic azithromycin (a member of the macrolide class of antibiotics that inhibit protein synthesis). Because the organism takes so long to grow in the laboratory (5–12 days) and because the organism is hard to find late in the disease, a blood sample was also drawn to test for anti–B. pertussis immunoglobulin A antibody. By the next day the serum test was positive for B. pertussis antibodies. The pathogen eventually also grew in the culture. Despite extensive efforts at vaccination, more than 41,000 cases of whooping cough were reported in the United States in 2012.

Several of the protein exotoxins produced by Bordetella pertussis act by disrupting signal transduction. Which of the following exotoxin-target pairs is NOT properly matched? a. Cholera toxin—disrupts signal transduction, increasing cAMP synthesis much like in pertussis b. Anthrax toxin—forms pores in membranes, allowing bacteria to escape vacuoles c. Shiga toxin—inhibits protein synthesis, leading to hemolytic uremic syndrome d. Staphylococcal alpha toxin—forms pores in membranes, leading to lysis of blood cells ANS: B DIF: Difficult REF: Case History 18.1 OBJ: 18.3b Explain the modes of action for staphylococcal alpha toxin, cholera toxin, diphtheria toxin, Shiga toxin, and anthrax toxin.

MSC: Remembering COMPLETION 1. Most pathogenicity island genes were acquired by ________ transmission.

ANS: horizontal DIF: Easy REF: 18.1 OBJ: 18.1a Differentiate between pathogenicity genes and pathogenicity islands.

MSC: Understanding 2. Organized, high-density communities of cells that embed themselves in self-made exopolymer matrices are called ________.

ANS: biofilms DIF: Easy REF: 18.2 MSC: Understanding

OBJ: 18.2d Discuss the role of biofilms in pathogenicity.

3. Toxins made and secreted by bacterial cells are called ________ while toxins contained within the bacterial cell wall are called ________.

ANS: exotoxins; endotoxins

DIF: Moderate REF: 18.3 MSC: Understanding

OBJ: 18.3c Differentiate endotoxin from exotoxin.

4. Organisms that can survive inside or outside host cells are called ________ pathogens.

ANS: facultative intracellular DIF: Easy REF: 18.5 OBJ: 18.5a Distinguish extracellular pathogens from facultative and obligate intracellular pathogens.

MSC: Understanding 5. Some microbes use tiny molecular syringes called ________ to inject proteins directly into the host cytoplasm.

ANS: type III secretions DIF: Easy REF: 18.4 OBJ: 18.4a Differentiate type II, type III, and type IV secretion systems used to export exotoxins/effector proteins.

MSC: Understanding SHORT ANSWER 1. Label the figure below with where the Tetanus, Shiga, and Cholera toxins affect cellular function.

ANS: Tetanus toxin: affects host cell exocytosis Shiga toxin: affects host cell cytoskeleton alterations Cholera toxin: affects host cell signal transduction disruption DIF: Difficult REF: 18.3 OBJ: 18.3a Describe the nine basic cellular targets for bacterial toxins.

MSC: Applying 2. Using the figure below, explain how Salmonella enterica uses its type III secretion systems to invade the eukaryotic host cell and become an intracellular parasite.

ANS: Salmonella attaches to host M cells within the intestinal wall. Once attached, Salmonella uses a type III secretion system to deliver protein toxins into the host cell. These effector proteins interfere with signal transduction in the host cell. They interfere with the cytoskeleton, which causes ruffling in the eukaryotic membrane around the extracellular microbe, which starts the process of engulfment. Once inside the cell, Salmonella uses another type III secretion system to alter vesicle trafficking to avoid destruction. This allows the organism to survive inside host cells without being destroyed.

DIF: Difficult REF: 18.5 OBJ: 18.5d Explain why and how intracellular pathogens distinguish between intracellular and extracellular existence.

MSC: Applying 3. The figure below illustrates T. brucei inside a host. Explain what is happening in the figure.

ANS: This figure illustrates antigenic variation as an immune-avoidance mechanism.

A: The pathogen is displaying one type of antigen.

B: The host has generated antibodies to the original antigen.

C: The generated host antibodies against the original antigen kill off some of the pathogen; however, the pathogen begins to display different antigens that are not recognizable to the original antibodies.

D: Pathogens with the newly generated antibodies grow unregulated until the immune system makes more antibodies.

DIF: Difficult REF: 18.7 OBJ: 18.7c Explain several mechanisms protozoans use to avoid the immune system.

MSC: Applying

4. Draw and label an AB toxin. List two diseases that are caused by AB toxins.

ANS: The students’ drawings should show one A subunit and a pentamer B subunit, similar to what is shown in Figure 18.11.

Diseases they can list include cholera, traveler’s diarrhea, diphtheria, and anthrax.

DIF: Difficult REF: 18.3 OBJ: 18.3b Explain the modes of action for staphylococcal alpha toxin, cholera toxin, diphtheria toxin, Shiga toxin, and anthrax toxin.

MSC: Applying 5. Explain the difference between antigenic drift and antigenic shift. How might antigenic shift relate to the generation of a new flu pandemic?

ANS: Antigenic drift is the accumulation of random mutations in the RNA genome that can cause minor changes in hemagglutinin antigen structures. This occurs annually and is the reason we must have a seasonal flu shot. Antigenic shift, on the other hand, occurs when the flu virus undergoes a major genetic alteration by acquiring different RNA strands. This change could result in a new potential pandemic strain.

Antigenic shift leads to the generation of a novel virus strain to which no one on Earth would be immune. It occurs when two strains of flu virus infect the same cell. Reassortment can occur, generating a chimeric virus that may have new pairings between the HA and N genes. The new virus may then jump to humans.

DIF: Difficult REF: 18.6 OBJ: 18.6a Discuss antigenic variation in rhinovirus and influenza viruses.

MSC: Applying 6. CASE HISTORY Will, a formerly rambunctious five-year-old from San Francisco, was taken to the emergency department after having a severe cough for two weeks. His illness started as a runny nose, dry cough, and low-grade fever. But within days the coughing would come in violent fits lasting up to one minute (called a paroxysm). The nurse practitioner attending Will observed one of these fits. Unable to breathe between coughs, the boy became cyanotic (turned blue). When the staccato of coughs finally ended, Will gasped, desperate for breath. The air rushing to fill his lungs made an ear-piercing whooping sound. This telltale “whoop” led the nurse practitioner to suspect whooping cough, a disease highly contagious in its early stages. In the later stages (greater than four weeks) the patient is no longer contagious because the bacterial agent, Bordetella pertussis, has succumbed to the immune response. However, the telltale cough will persist for weeks while the lungs repair the damage caused by the pertussis toxins. The nurse practitioner, now wearing a mask, took a nasopharyngeal swab sample for bacteriological culture and prescribed the antibiotic azithromycin (a member of the macrolide class of antibiotics that inhibit protein synthesis). Because the organism takes so long to grow in the laboratory (5–12 days) and because the organism is hard to find late in the disease, a blood sample was also drawn to test for anti–B. pertussis immunoglobulin A antibody. By the next day the serum test was positive for B. pertussis antibodies. The pathogen eventually also grew in the culture. Despite extensive efforts at vaccination, more than 41,000 cases of whooping cough were reported in the United States in 2012.

As a Gram-negative bacterium, Bordetella pertussis produces endotoxin. Why is this toxin not a major contributor to the disease signs and symptoms associated with pertussis?

ANS:

Endotoxin is released when Gram-negative cells are lysed, or in small amounts when they divide. In an active infection, in which most cells remain intact, the immune system will not be exposed to large quantities of endotoxin.

DIF: Moderate REF: Case History 18.1 OBJ: 18.3c Differentiate endotoxin from exotoxin.

MSC: Analyzing

7. CASE HISTORY Shakia was in her fourth month of pregnancy and excited to become a mother. A 33-year-old African American from Indianapolis, Shakia had been in good health until about a week ago, when she started to experience abdominal pain, fever, muscle aches, and diarrhea. She visited her obstetrician to make sure it was nothing serious. When the obstetrician asked whether she had eaten anything unusual in the past few weeks, Shakia recalled eating some soft Mexican cheese about three weeks earlier during a visit to Oregon with her husband. The physician sent a sample of Shakia’s blood and stool to the local diagnostic laboratory and prescribed the antibiotic ampicillin as treatment. The lab reported finding a Gram-positive, non–spore-forming bacillus called Listeria monocytogenes in both the fecal and blood samples. Shakia had mild gastroenteritis and septicemia. The septicemia placed her unborn child at serious risk of infection because this bacterium can cross the placental barrier. If not treated quickly, an infected fetus has a 70% chance of dying from meningitis and multiple organ system failure. The doctor hoped she treated Shakia in time.

Is Listeria monocytogenes an extracellular, facultative intracellular, or obligate intracellular pathogen?

Describe the features of infection that support your conclusion.

ANS: It is a facultative intracellular pathogen. Surviving environmentally allows the organism to be transmitted through foods like unpasteurized cheeses. It is also known to survive intracellularly, escaping the phagosome and utilizing intracellular transport mechanisms to cross the placental barrier.

DIF: Moderate REF: Case History 18.2 OBJ: 18.5a Distinguish extracellular pathogens from facultative and obligate intracellular pathogens.

MSC: Analyzing

Chapter 19: Infections of the Skin and Eye LEARNING OBJECTIVES 19.1a List the different cellular components of the skin and their functions.

19.1b Describe the structural similarities and differences between dermis and epidermis.

19.1c Describe the role of different components of the skin in disease prevention.

19.1d Distinguish between the internal and external parts of the eye.

19.2a Classify viruses that cause skin rashes on the basis of their genomic structure.

19.2b Explain the pathogenesis of viral skin infection sequelae.

19.2c Outline how to diagnose the causative agent of a viral skin infection according to the patient’s signs and symptoms.

19.2d Recommend treatment and prevention options for different viral skin infections.

19.3a Name the bacterial pathogens that cause common skin infections.

19.3b Categorize skin infections by the physiology of the bacteria causing them.

19.3c List clinical and laboratory means of diagnosing bacterial skin infections.

19.3d Develop a prevention and treatment plan for bacterial skin infections.

19.4a Outline common fungal skin infections according to their etiology.

19.4b Compare dermatophytes with other fungi that commonly infect the skin.

19.4c Explain how common fungal infections are diagnosed clinically.

19.5a Discuss why Pseudomonas aeruginosa is a common cause of wound infections.

19.5b Categorize organisms that are commonly isolated from diabetic foot wounds on the basis of their Gram stain status.

19.5c Explain the roles of anaerobic and aerobic bacteria in the pathogenesis of gas gangrene.

19.6a Identify viral, bacterial, and fungal causes of eye infections.

19.6b Describe the symptoms and etiologies of “pink eye.”

19.6c Explain how the pathogenesis of infectious keratitis differs from that of endophthalmitis.

19.6d Outline the relationship between corneal epithelium and fungal keratitis.

MULTIPLE CHOICE 1. Which of the following displays a pus-filled raised lesion?

a. 1 b. 2

c. 3 d. 4

ANS: D DIF: Moderate REF: 19.2 OBJ: 19.2b Explain the pathogenesis of viral skin infection sequelae.

MSC: Applying

2. Chickenpox is caused by a very contagious herpes virus that infects epidermal cells. Which of the following is characteristic of a chickenpox infection?

a. 1 b. 2

c. 3 d. 4

ANS: B DIF: Difficult REF: 19.2 OBJ: 19.2b Explain the pathogenesis of viral skin infection sequelae.

MSC: Applying 3. Which of the following lists the layers of the skin in the correct order from deepest to superficial? a. stratum basale, stratum spinosum, stratum granulosum, stratum corneum b. stratum corneum, stratum granulosum, stratum spinosum, stratum basale c. stratum granulosum, stratum corneum, stratum basale, stratum spinosum d. stratum spinosum, stratum basale, stratum corneum, stratum granulosum ANS: A DIF: Easy REF: 19.1 OBJ: 19.1b Describe the structural similarities and differences between dermis and epidermis.

MSC: Understanding 4. All of the following are protective features of the skin EXCEPT a. Langerhans cells in the epidermis. b. that it is the largest organ and forms a chemical barrier. c. keratinocytes secreting keratin. d. melanocytes producing melanin.

ANS: B DIF: Moderate REF: 19.1 OBJ: 19.1a List the different cellular components of the skin and their functions.

MSC: Analyzing 5. Which of the following are INCORRECTLY matched? a. varicella zosters—chickenpox c. poxvirus—fever blisters b. HHV6—roseola d. parvovirus—fifth disease ANS: C DIF: Moderate REF: 19.2 OBJ: 19.2a Classify viruses that cause skin rashes on the basis of their genomic structure.

MSC: Remembering 6. Heather, an eight-year-old girl, has scabs and pus-filled vesicles on her face and throat. Three weeks earlier she had visited her grandmother, who had shingles. What infection does Heather have? a. chickenpox c. rubella b. measles d. fever blisters ANS: A DIF: Easy REF: 19.2 OBJ: 19.2c Outline how to diagnose the causative agent of a viral skin infection according to the patient’s signs and symptoms.

MSC: Analyzing 7. Koplik spots are a diagnostic indicator of

a. chickenpox. b. smallpox.

c. measles. d. rubella.

ANS: C DIF: Easy REF: 19.2 OBJ: 19.2c Outline how to diagnose the causative agent of a viral skin infection according to the patient’s signs and symptoms.

MSC: Remembering 8. All of the following are transmitted via the respiratory route EXCEPT a. smallpox. c. measles. b. chickenpox. d. warts.

ANS: D DIF: Easy REF: 19.2 OBJ: 19.2b Explain the pathogenesis of viral skin infection sequelae.

MSC: Remembering 9. Measles and German measles (rubella) are similar in that a. they have a similar type of rash. b. they are caused by the same virus. c. encephalitis is a possible complication. d. they can be controlled by vaccination.

ANS: D DIF: Difficult REF: 19.2 OBJ: 19.2d Recommend treatment and prevention options for different viral skin infections.

MSC: Analyzing 10. Which of the following is NOT caused by HSV-1? a. cold sores c. herpes whitlow b. canker sores d. herpes encephalitis ANS: B DIF: Moderate REF: 19.2 OBJ: 19.2c Outline how to diagnose the causative agent of a viral skin infection according to the patient’s signs and symptoms.

MSC: Remembering 11. Which of the following is used to treat shingles? a. penicillin c. acyclovir b. sulfonamide d. fungicide ANS: C DIF: Moderate REF: 19.2 OBJ: 19.2d Recommend treatment and prevention options for different viral skin infections.

MSC: Understanding 12. Staphylococcus aureus is responsible for all of the following EXCEPT a. boils. c. acne. b. carbuncles. d. pimples.

ANS: C DIF: Easy REF: 19.3 OBJ: 19.3a Name the bacterial pathogens that cause common skin infections.

MSC: Remembering 13. The etiological agent of acne is a. Staphylococcus aureus. b. Streptococcus pyogenes.

c. Bacillus anthrasis. d. Propionibacterium acnes.

ANS: D DIF: Easy REF: 19.3 OBJ: 19.3a Name the bacterial pathogens that cause common skin infections.

MSC: Remembering

14. All of the following are virulence factors associated with S. pyogenes EXCEPT a. lipopolysaccharide. c. M protein. b. capsule. d. lipoteichoic acid.

ANS: A DIF: Moderate REF: 19.3 OBJ: 19.3b Categorize skin infections by the physiology of the bacteria causing them.

MSC: Remembering 15. Topical retinoids and antibiotics are commonly used to treat a. cellulitis. c. erysipelas. b. acne. d. impetigo.

ANS: B DIF: Moderate REF: 19.3 OBJ: 19.3d Develop a prevention and treatment plan for bacterial skin infections.

MSC: Understanding 16. Which of the following is NOT true about gas gangrene? a. The organism produces considerable amounts of gas. b. The causative agent is Clostridium perfringens. c. The organism only grows on live tissue. d. The organism is found in the environment and in the intestines.

ANS: C DIF: Difficult REF: 19.3 OBJ: 19.3c List clinical and laboratory means of diagnosing bacterial skin infections.

MSC: Analyzing 17. All of the following cause conjunctivitis EXCEPT a. Chlamydia trachomatis. c. Neisseria gonorrhoeae. b. Streptococcus pyogenes. d. Haemophilus influenza.

ANS: B DIF: Difficult REF: 19.6 OBJ: 19.6a Identify viral, bacterial, and fungal causes of eye infections.

MSC: Remembering 18. Which of the following is used to treat ophthalmia neonatorum? a. penicillin c. sulfonamide b. acyclovir d. erythromycin ANS: D DIF: Moderate REF: 19.6 OBJ: 19.6a Identify viral, bacterial, and fungal causes of eye infections.

MSC: Remembering 19. Inflammation of the thin clear membrane lining the eyelid and eye is properly termed a. keratitis. c. conjunctivitis. b. trachoma. d. ophthalmia neonatorum.

ANS: C DIF: Moderate REF: 19.6 OBJ: 19.6b Describe the symptoms and etiologies of “pink eye.”

MSC: Understanding 20. All of the following are used to treat chickenpox EXCEPT a. aspirin. c. antihistamines. b. calamine lotion. d. oatmeal baths.

ANS: A

DIF: Moderate

REF: 19.2

OBJ: 19.2d Recommend treatment and prevention options for different viral skin infections.

MSC: Remembering 21. All of the following are characteristic of Pseudomonas aeruginosa EXCEPT a. a Gram-positive cell wall. b. resistance to many types of antibiotics. c. production of pyocyanin. d. exotoxin production.

ANS: A DIF: Moderate REF: 19.5 OBJ: 19.5a Discuss why Pseudomonas aeruginosa is a common cause of wound infections.

MSC: Remembering 22. The greatest single cause of infectious blindness is a. neonatal gonorrheal ophthalmia. c. trachoma. b. keratoconjunctivitis. d. Pink eye.

ANS: C DIF: Easy REF: 19.6 OBJ: 19.6a Identify viral, bacterial, and fungal causes of eye infections.

MSC: Remembering 23. A patient is brought to the hospital suffering from a MRSA infection. Which of the following is the best treatment option? a. acyclovir c. methicillin b. penicillin d. vancomycin ANS: D DIF: Difficult REF: 19.3 OBJ: 19.3c List clinical and laboratory means of diagnosing bacterial skin infections.

MSC: Applying 24. The figure below shows the fungi Fusarium. When accidentally introduced into the eye, what type of infection does this organism cause?

a. fungal keratitis b. parasitic keratitis

c. allergic conjunctivitis d. trachoma

ANS: A DIF: Moderate REF: 19.6 OBJ: 19.6d Outline the relationship between corneal epithelium and fungal keratitis.

MSC: Applying 25. All of the following are methods used to treat C. perfringens infection EXCEPT a. amputation. c. antibiotic therapy alone. b. a hyperbaric chamber. d. debridement.

ANS: C DIF: Moderate REF: 19.5 OBJ: 19.5c Explain the roles of anaerobic and aerobic bacteria in the pathogenesis of gas gangrene.

MSC: Analyzing 26. Applying your knowledge to the figure below, if a herpes zoster infection is left untreated in an immunocompromised patient, which part of the eye can be damaged?

a. cornea b. retina

c. optic nerve d. lens

ANS: B DIF: Easy REF: 19.6 OBJ: 19.6b Describe the symptoms and etiologies of “pink eye.”

MSC: Applying 27. Sterile maggot therapy is often used to treat which condition? a. diabetic wounds c. conjunctivitis b. acne d. keratitis ANS: A DIF: Easy REF: 19.5 OBJ: 19.5b Categorize organisms that are commonly isolated from diabetic foot wounds on the basis of their Gram stain status.

MSC: Understanding 28. Fungal skin diseases are diagnosed based on a. PCR. b. KOH preparation of skin scrapes.

c. Gram-positive stain. d. Gram-negative stain.

ANS: B DIF: Easy REF: 19.4 OBJ: 19.4c Explain how common fungal infections are diagnosed clinically.

MSC: Understanding 29. All of the following are classified as dermatophytic fungi EXCEPT a. Malassezia. c. Trichophyton. b. Epidermophyton. d. Microsporum.

ANS: A DIF: Easy REF: 19.4 OBJ: 19.4b Compare dermatophytes with other fungi that commonly infect the skin.

MSC: Understanding 30. Which of the following statements about fungi is true? a. Fungi include yeasts and bacteria. b. Fungi are eukaryotic microbes. c. Dermatophytes do not grow on skin.

d. Fungi can be named after the location of the infection.

ANS: B DIF: Moderate REF: 19.4 OBJ: 19.4a Outline common fungal skin infections according to their etiology.

MSC: Understanding 31. Keratitis is inflammation of the a. lens. b. retina.

c. cornea. d. sclera.

ANS: C DIF: Easy REF: 19.6 OBJ: 19.6c Explain how the pathogenesis of infectious keratitis differs from that of endophthalmitis.

MSC: Remembering 32. A 17-year-old boy has pus-filled cysts on his face and upper back. Microscopic examination reveals Gram-positive rods. This infection is caused by a. herpes simplex virus. c. Staphylococcus aureus. b. Propionibacterium acnes. d. Streptococcus pyogenes.

ANS: B DIF: Easy REF: 19.3 OBJ: 19.3c List clinical and laboratory means of diagnosing bacterial skin infections.

MSC: Applying 33. Which of the following is INCORRECTLY matched? a. Haemophilus influenzae—pink eye b. Pseudomonas—conjunctivitis c. Chlamydia gonorrhoeae—trachoma d. Neisseria gonorrhoeae—respiratory infection ANS: D DIF: Moderate REF: 19.5 OBJ: 19.5a Discuss why Pseudomonas aeruginosa is a common cause of wound infections.

MSC: Understanding 34. A 35-year-old woman has a red, raised rash on the inside of her thighs. Gram-stained scrapings show large budding cells with pseudohyphae. The infection is caused by a. Candida albicans. c. varicella—zoster virus. b. herpes simplex virus. d. Staphylococcus aureus.

ANS: A DIF: Easy REF: 19.4 OBJ: 19.4a Outline common fungal skin infections according to their etiology.

MSC: Applying 35. A 65-year-old man has pus-filled vesicles distributed over his back in the upper right quadrant, his right shoulder, and the upper right quadrant of his chest. His symptoms are most likely due to a. Candida albicans. c. varicella—zoster virus. b. herpes simplex virus. d. Staphylococcus aureus.

ANS: C DIF: Easy REF: 19.2 OBJ: 19.2b Explain the pathogenesis of viral skin infection sequelae.

MSC: Applying 36. A 40-year-old woman has vesicles and scabs over her forehead. Microscopic examination of skin scrapings shows Gram-positive cocci in clusters. The etiology is a. Staphylococcus aureus. c. Candida. b. Streptococcus pyogenes. d. herpes.

ANS: A DIF: Easy REF: 19.3 OBJ: 19.3c List clinical and laboratory means of diagnosing bacterial skin infections.

MSC: Applying 37. Which of the following is used to treat candidiasis of the skin or mucous membranes? a. penicillin c. acyclovir b. sulfonamide d. imidazole ANS: D DIF: Moderate REF: 19.4 OBJ: 19.4c Explain how common fungal infections are diagnosed clinically.

MSC: Understanding 38. Which of the following statements about congenital rubella syndrome is FALSE? a. It can be prevented by vaccinating women prior to pregnancy. b. It may result in deafness, blindness, and mental retardation. c. It may be fatal to the unborn child. d. It does not occur with subclinical infection.

ANS: D DIF: Moderate REF: 19.2 OBJ: 19.2d Recommend treatment and prevention options for different viral skin infections.

MSC: Analyzing 39. Vaccination for rubella is recommended because a. it has a high mortality rate in school-age children. b. death from secondary infections is common. c. there is a high incidence of congenital infections. d. It is no longer recommended; rubella has been eradicated.

ANS: C DIF: Easy REF: 19.2 OBJ: 19.2d Recommend treatment and prevention options for different viral skin infections.

MSC: Understanding 40. Which of the following is the cause of a fungal infection on the scalp? a. tinea capitis c. tinea pedis b. tinea corporis d. tinia cruris ANS: A DIF: Easy REF: 19.4 OBJ: 19.4b Compare dermatophytes with other fungi that commonly infect the skin.

MSC: Understanding 41. CASE HISTORY

One weekend in June, Cassi was camping with her three children. She suffered a minor cut on her finger, which she bandaged properly. She also injured the left side of her body while playing sports with her kids. Not thinking much of either of her minor injuries, she went to bed. Two days later, Cassi was extremely ill. Her symptoms included vomiting, diarrhea, and a fever. She was also in severe pain where she had injured her side, and the area had begun to bruise (the skin did not look broken). By the next day, she could barely get out of bed, and by the end of the night, she was breathing with difficulty and could not see. Her side began to leak fluid and blood. Cassi was admitted to the hospital in septic shock, with no detectable blood pressure. She was given vasopressors (medications that constrict the blood vessels) to raise her blood pressure to the normal level. An infectious disease specialist diagnosed the problem as necrotizing fasciitis, and Cassi was rushed into surgery. In an effort to save her life, about 7% of her body surface was removed. Because the large wound infection in her side would need to resolve before a skin graft could be performed to repair it, the hole in Cassi’s body was left wide open. Meanwhile, the continued use of vasopressors caused gangrene in her fingers and lower extremities. After nearly three months and several operations, including amputation, Cassi recovered.

Which organism would be the most likely to be identified in a laboratory culture of Cassi’s wound? a. Staphylococcus epidermidis c. Clostridium perfringens b. Streptococcus pyogenes d. Salmonella enterica ANS: B DIF: Moderate REF: Case History 19.3 OBJ: 19.3a Name the bacterial pathogens that cause common skin infections.

MSC: Analyzing COMPLETION 1. A skin rash accompanied by systemic symptoms such as fever, malaise, and headache is referred to as ________, while skin rashes on the mucous membranes are called ________.

ANS: exanthema; enanthems DIF: Easy REF: 19.1 OBJ: 19.1b Describe the structural similarities and differences between dermis and epidermis.

MSC: Understanding 2. Necrotizing fasciitis is often caused by ________.

ANS: Streptococcus pyogenes DIF: Moderate REF: 19.3 OBJ: 19.3a Name the bacterial pathogens that cause common skin infections.

MSC: Remembering 3. Ophthalmia neonatorum is a serious eye disease of infants caused by ________.

ANS: Neisseria gonorrhoeae DIF: Difficult REF: 19.6 OBJ: 19.6a Identify viral, bacterial, and fungal causes of eye infections.

MSC: Remembering 4. Fungi that live on human skin are called ________.

ANS: dermatophytes

DIF: Easy REF: 19.4 OBJ: 19.4b Compare dermatophytes with other fungi that commonly infect the skin.

MSC: Understanding 5. A sight-threatening inflammation of the cornea is referred to as ________.

ANS: keratitis DIF: Difficult REF: 19.6 OBJ: 19.6c Explain how the pathogenesis of infectious keratitis differs from that of endophthalmitis.

MSC: Understanding SHORT ANSWER 1. Smallpox is a deadly disease caused by the variola virus. Currently, the only stocks of smallpox are located in strategic centers across the United States. Discuss the pros and cons of destroying these remaining smallpox stocks.

ANS: Pro: By eliminating all remaining stocks of smallpox, you can truly say that the organism has been eradicated from the planet.

Con: Since smallpox is classified as a bioterrorism agent, if this organism were used in an attack, most of the current population would not have protective immunity against this pathogen because we no longer vaccinate against it.

DIF: Difficult REF: 19.2 OBJ: 19.2d Recommend treatment and prevention options for different viral skin infections.

MSC: Evaluating 2. List the disease symptoms and virulence factors associated with Pseudomonas infections. Why can Pseudomonas be difficult to control in a hospital environment?

ANS: P. aeruginosa is a cause of serious wound infections owing to its wealth of virulence factors and its high level of antibiotic resistance. It is ubiquitous in the environment and is an opportunistic pathogen.

This organism also makes and secretes exotoxin A and exotoxin S, which are ADP-ribosyltransferases that interfere with host-signaling pathways and protein synthesis. P. aeruginosa also secretes phospholipases and proteases that contribute to tissue invasion and disease. This organism is also resistant to a great many antibiotics, making treatment of burn wounds difficult.

DIF: Difficult REF: 19.5 OBJ: 19.5a Discuss why Pseudomonas aeruginosa is a common cause of wound infections.

MSC: Analyzing 3. Using the figure below, label the following cellular components of the skin and describe their function.

A. keratinocytes B. dermis C. epidermis D. Langerhans cells E. hair follicle F. sweat gland

ANS: A. keratinocytes: cells that make fibrous protein called keratin B. dermis: deep layer C. epidermis: most superficial layer, consists of five layers D. Langerhans cells: specialized dendritic cells located in the skin E. hair follicle: common portal of entry for organisms F. sweat gland: common portal of entry for organisms DIF: Moderate REF: 19.1 OBJ: 19.1a List the different cellular components of the skin and their functions.

MSC: Applying 4. Explain the cycle of acne. What is the causative agent and why are some individuals more prone to acne than others?

ANS: Acne usually affects the face and typically results from blocked hair follicles or pores. Inflammatory acne arises from macules, papules, pustules, and nodules.

Several factors contribute to acne development. The first is genetic predisposition in which epithelial cells in a follicle replicate more often than normal, which contributes to plugging of the follicle. High levels of hormones can cause hyperproliferation and excess sebum production. Sebum is a waxy, oily substance secreted by sebaceous glands that plug the follicle. Gram-positive, anaerobic bacterium P. acnes plays an important role. P. acnes uses triglycerides in sebum as a nutrient.

DIF: Difficult REF: 19.3 OBJ: 19.3d Develop a prevention and treatment plan for bacterial skin infections.

MSC: Evaluating 5. Compare and contrast the virulence factors associated with Staphylococcus aureus and Streptococcus pyogenes. Which of these agents is the most difficult to treat? Explain your answer.

ANS: S. aureus and S. pyogenes have some similar virulence factors. Both possess a capsule that helps them avoid host defenses such as phagocytosis. They both make and secrete a number of exotoxins that help to break down host defenses.

S. aureus can cause serious skin infection. This bacterium possesses a number of enzymes that contribute to disease, including coagulase, TSST-1 (a superantigen), and exfoliative toxin that causes a blistering disease in children.

S. pyogenes can cause necrotizing fasciitis. This bacterium possesses several virulence factors such as a capsule, pilus-like M protein, lipoteichoic acid in its cell wall (which helps the bacteria adhere to pharyngeal epithelial cells), enzymes that lyse blood cells and degrade DNA, fibrin, and connective tissue.

Based on antibiotic resistance, Staphylococcus aureus is more difficult to treat.

DIF: Moderate REF: 19.3 OBJ: 19.3b Categorize skin infections by the physiology of the bacteria causing them.

MSC: Analyzing 6. CASE HISTORY Jennifer remembered the day she was shot, but not the day they had to remove her leg. She was camping in the middle of the Black Hills of South Dakota when an unseen hunter tried to shoot a deer.

He missed his prey, but the errant bullet traveled a great distance and tore through Jennifer’s thigh. In tremendous pain, Jennifer fashioned a tourniquet to stop the bleeding and then struggled two days to hike the ten miles back to civilization. By the time she arrived at a hospital, the wound and underlying muscle were clearly infected. The area around the wound was reddened and contained fluid-filled blisters, and parts were starting to turn black. The drainage coming from the wound contained pus and was foul smelling, all signs of gas gangrene. The surgical team worked to debride the dead tissue and placed her on intravenous antibiotic therapy (clindamycin). The microbiology laboratory reported finding Clostridium perfringens in the samples sent. Despite treatment, including hyperbaric oxygen, the infection continued spreading further up her leg. The surgeons finally decided that amputation was the only way to save her life.

Why might hyperbaric oxygen have been suggested as a treatment for Jennifer following the return of her lab results?

ANS: C. perfringens is a true saprophyte, growing only on dead tissue. Infections usually start out mixed with aerobic organisms that consume oxygen and provide an anaerobic environment for the clostridia.

DIF: Difficult REF: Case History 19.4 OBJ: 19.5c Explain the roles of anaerobic and aerobic bacteria in the pathogenesis of gas gangrene.

MSC: Evaluating 7. CASE HISTORY

Leili, a three-year-old girl, was brought to the pediatrician by her mother, who was worried about the rash on Leili’s lip. It started four days earlier as a little bump above her lip that spread to the corner of her mouth. The base of the rash was red and covered by pustules. The little girl said that her rash hurt, and the clinician noticed a honey-colored crust on the ruptured pustules. Leili’s mother said that her daughter had not been trying to scratch the rash, nor was the area around it hot to the touch.

Leili’s mother was told that her little girl had impetigo, a skin infection often caused by bacteria called staphylococci, although streptococci can also cause it. The doctor gently swabbed a sample from one of Leili’s sores and sent it to the lab, where the causative agent would be identified and its antibiotic susceptibility determined. She explained that impetigo is a very contagious disease, and she gave Leili’s mother a topical antibiotic to use. Treating topically rather than orally would accomplish two goals: Topical application would reduce the chance that the bacteria would develop drug resistance, and because Leili had a very mild case of impetigo, the antibiotic in the gel should easily penetrate the pustules and kill the organism. Leili and her mother left but returned in a week for a follow-up exam.

The “rash” was gone, replaced by Leili’s smile. The pediatrician explained that the cause was in fact methicillin-sensitive Staphylococcus aureus (MSSA), not MRSA. Leili’s mother in turn reported that another child at Leili’s day care had impetigo before Leili, and that is where Leili probably acquired the infection.

Leili was suffering from nonbullous impetigo; however, a bullous form also exists. How would you distinguish the two and how would you approach the creation of a treatment plan for this disease?

ANS: Diagnosis of impetigo is made by clinical signs and symptoms (yellow fluid-filled blisters). It is important to treat impetigo to avoid complications such as scalded skin syndrome. Leili was treated with a topical antibiotic because her case was mild. Oral antibiotics are better suited for more severe cases. The antibiotic used should be active against Gram-positive cocci.

DIF: Moderate REF: Case History 19.2 OBJ: 19.3d Develop a prevention and treatment plan for bacterial skin infections.

MSC: Evaluating

Chapter 20: Infections of the Respiratory Tract LEARNING OBJECTIVES 20.1a List the anatomical differences between the upper and lower respiratory tracts.

20.1b Describe the relationship of eyes, ears, and nose with the upper airways.

20.1c Explain the role of the mucociliary elevator in respiratory infection processes.

20.2a Compare and contrast the signs and symptoms of upper and lower respiratory tract infections.

20.2b Describe the role of mutations in the genesis of influenza pandemics.

20.2c List the risk factors for upper and lower respiratory tract infections.

20.2d Identify the etiology of the major viral respiratory infections based on their presentation.

20.3a List the bacterial etiologies of respiratory tract diseases and the disease’s anatomical location.

20.3b Describe the relationships between host and bacteria that contribute to the pathogenesis of respiratory tract infections.

20.3c Compare and contrast clinical presentations of bacterial infections of the respiratory tract.

20.3d Develop a prevention plan for different bacterial respiratory pathogens.

20.4a Identify the most common etiologies of fungal lower respiratory tract infections.

20.4b Describe the differences between fungal and bacterial lower respiratory tract infections.

20.4c Name the risk factors associated with fungal respiratory tract infections.

MULTIPLE CHOICE 1. The structure indicated on the figure below is

a. a bronchiole. b. the trachea.

c. a main bronchus. d. an alveolar duct.

ANS: C DIF: Easy REF: 20.1 OBJ: 20.1a List the anatomical differences between the upper and lower respiratory tracts.

MSC: Understanding

2. Which of the following infections would affect the upper respiratory tract but NOT the lower respiratory tract? a. the common cold c. tuberculosis b. pneumonia d. bronchitis ANS: A DIF: Moderate REF: 20.1 OBJ: 20.1a List the anatomical differences between the upper and lower respiratory tracts.

MSC: Applying 3. Which of the following infections would affect the lower respiratory tract but NOT the upper respiratory tract? a. acute otitis media c. streptococcal pharyngitis b. sinusitis d. atypical pneumonia ANS: D DIF: Moderate REF: 20.1 OBJ: 20.1a List the anatomical differences between the upper and lower respiratory tracts.

MSC: Applying 4. Which of the following structures is considered part of the upper respiratory tract? a. trachea c. alveoli b. primary bronchi d. larynx ANS: D DIF: Easy REF: 20.1 OBJ: 20.1a List the anatomical differences between the upper and lower respiratory tracts.

MSC: Remembering 5. The structure indicated on the figure below is a(n)

a. sinus. b. lacrimal duct.

c. inner ear. d. Eustachian tube.

ANS: A DIF: Moderate REF: 20.1 OBJ: 20.1b Describe the relationship of eyes, ears, and nose with the upper airways.

MSC: Understanding 6. The significance of the anatomical difference shown in the figure below is that ________ are more prone to developing ________ infections.

a. adults; sinus b. children; sinus

c. adults; middle ear d. children; middle ear

ANS: D DIF: Moderate REF: 20.1 OBJ: 20.1b Describe the relationship of eyes, ears, and nose with the upper airways.

MSC: Applying 7. The Eustachian tubes connect the upper respiratory tract to the a. sinuses. c. inner ears. b. middle ears. d. eyes.

ANS: B DIF: Easy REF: 20.1 OBJ: 20.1b Describe the relationship of eyes, ears, and nose with the upper airways.

MSC: Understanding 8. The eyes are connected to the upper respiratory tract by the a. pharynx. c. lacrimal ducts. b. Eustachian tube. d. sinuses.

ANS: C DIF: Moderate REF: 20.1 OBJ: 20.1b Describe the relationship of eyes, ears, and nose with the upper airways.

MSC: Understanding 9. A common home remedy used to treat a common cold is eating chicken soup or chicken broth. Why might this home remedy be useful? a. Broth helps to prevent dehydration and thins mucus secretions. b. The salt in broth draws water out of bacterial cells by osmosis. c. Chicken meat contains antiviral properties. d. Broth removes the top epithelial cell layers that contain viral particles.

ANS: A DIF: Difficult REF: 20.1 OBJ: 20.1c Explain the role of the mucociliary elevator in respiratory infection processes.

MSC: Applying 10. A secondary bacterial infection is most likely in a patient who a. smokes cigarettes. c. breathes dry air. b. breathes humidified air. d. has thin mucus secretions.

ANS: A DIF: Moderate REF: 20.1 OBJ: 20.1c Explain the role of the mucociliary elevator in respiratory infection processes.

MSC: Applying 11. Nicotine in cigarette smoke paralyzes the cilia found on epithelium within the respiratory tract. The normal function of these cilia is that they

a. b. c. d.

produce mucus that traps microorganisms. help to warm incoming air. aid in moving mucus to the nasal and oral cavities. contain macrophages that target microorganisms.

ANS: C DIF: Moderate REF: 20.1 OBJ: 20.1c Explain the role of the mucociliary elevator in respiratory infection processes.

MSC: Understanding 12. A viral disease of the lower respiratory tract would likely present with a. runny nose. c. facial pain. b. sinus congestion. d. cough.

ANS: D DIF: Easy REF: 20.2 OBJ: 20.2a Compare and contrast the signs and symptoms of upper and lower respiratory tract infections.

MSC: Applying 13. Of the viral respiratory diseases below, which is LEAST likely to present with a fever? a. the common cold c. influenza b. croup d. respiratory syncytial disease ANS: A DIF: Easy REF: 20.2 OBJ: 20.2a Compare and contrast the signs and symptoms of upper and lower respiratory tract infections.

MSC: Understanding 14. As a result of an antigenic shift a. influenza is able to evade the host immune system by presenting a new hemagglutinin structure. b. the host immune system is better able to detect and respond to influenza viruses. c. the influenza viral protein M2 becomes hidden within the virion envelope. d. alpha 2,6 receptors are able to bind to the alpha 2,3 sialic acid residues.

ANS: A DIF: Moderate REF: 20.2 OBJ: 20.2b Describe the role of mutations in the genesis of influenza pandemics.

MSC: Applying 15. Antigenic shift is best described as a a. mixing of RNA segments to create a new form of the hemagglutinin gene in influenza. b. shift of influenza antigen from one geographic location to another. c. mutation that changes influenza RNA polymerase. d. shift that occurs when an avian strain of influenza infects a pig.

ANS: A DIF: Moderate REF: 20.2 OBJ: 20.2b Describe the role of mutations in the genesis of influenza pandemics.

MSC: Understanding 16. The most likely mutation to cause an influenza pandemic would be a mutation in a. the head of hemagglutinin. c. M2 protein inside the virion envelope. b. the stalk of hemagglutinin. d. influenza nucleoprotein.

ANS: A DIF: Difficult REF: 20.2 OBJ: 20.2b Describe the role of mutations in the genesis of influenza pandemics.

MSC: Applying 17. Coming into contact with respiratory secretions from an infected individual is LEAST likely to spread a. the common cold. c. influenza.

b. respiratory syncytial disease.

d. sinusitis.

ANS: D DIF: Easy REF: 20.2 OBJ: 20.2c List the risk factors for upper and lower respiratory tract infections.

MSC: Understanding 18. A virus that primarily causes disease in the very young and may lead to complications such as low blood pressure and seizures is a. type A influenza. c. SARS virus. b. rhinovirus. d. respiratory syncytial virus.

ANS: D DIF: Moderate REF: 20.2 OBJ: 20.2d Identify the etiology of the major viral respiratory infections based on their presentation.

MSC: Remembering 19. Croup is most frequently seen in a. the elderly. b. middle-aged adults.

c. adolescents. d. young children.

ANS: D DIF: Easy REF: 20.2 OBJ: 20.2d Identify the etiology of the major viral respiratory infections based on their presentation.

MSC: Remembering 20. Compared to individuals who receive vaccinations, individuals who do not receive any vaccinations are at higher risk of developing a. sinusitis. c. influenza. b. severe acute respiratory syndrome. d. croup.

ANS: C DIF: Moderate REF: 20.2 OBJ: 20.2c List the risk factors for upper and lower respiratory tract infections.

MSC: Analyzing 21. Respiratory syncytial virus and influenza are responsible for the majority of cases of a. bacterial pneumonia. c. sinusitis. b. viral pneumonia. d. kidney failure.

ANS: B DIF: Easy REF: 20.2 OBJ: 20.2d Identify the etiology of the major viral respiratory infections based on their presentation.

MSC: Understanding 22. A 23-year-old man arrives in the emergency room. He is in respiratory distress and is experiencing kidney failure and blood clots in one lung. His partner reports that he had a high fever, chills, and a cough for several days prior. The attending physician quickly orders a serum antibody test validated by the CDC when he suspects the individual may be infected with a. type B influenza. c. severe acute respiratory syndrome. b. respiratory syncytial virus. d. croup.

ANS: C DIF: Difficult REF: 20.2 OBJ: 20.2d Identify the etiology of the major viral respiratory infections based on their presentation.

MSC: Evaluating 23. A day-care worker reports that two young children have been coughing all day. She first noticed that both children had runny noses a few days ago but is not sure if they had fevers. She states that they both sound like barking seals. Most likely these children have a. the common cold. c. influenza. b. croup. d. respiratory syncytial disease.

ANS: B DIF: Moderate REF: 20.2 OBJ: 20.2d Identify the etiology of the major viral respiratory infections based on their presentation.

MSC: Applying 24. Due to the location of infection, bacterial sinusitis may lead to complications, including a. meningitis. c. bronchitis. b. pneumonia. d. epiglottitis.

ANS: A DIF: Easy REF: 20.3 OBJ: 20.3a List the bacterial etiologies of respiratory tract diseases and the disease’s anatomical location.

MSC: Applying 25. The most common cause of bacterial pharyngitis is a. Streptococcus pyogenes. c. Haemophilus influenzae. b. Streptococcus pneumoniae. d. Corynebacterium diphtheriae.

ANS: A DIF: Easy REF: 20.3 OBJ: 20.3a List the bacterial etiologies of respiratory tract diseases and the disease’s anatomical location.

MSC: Remembering 26. Acute otitis media is infection within the a. sinuses. b. outer ear.

c. middle ear. d. inner ear.

ANS: C DIF: Easy REF: 20.3 OBJ: 20.3a List the bacterial etiologies of respiratory tract diseases and the disease’s anatomical location.

MSC: Remembering 27. Which of the following organisms is an intracellular pathogen capable of preventing fusion of a phagosome with a lysosome after phagocytosis has occurred? a. Pseudomonas aeruginosa c. Mycobacterium tuberculosis b. Haemophilus influenzae d. Legionella pneumophila ANS: D DIF: Moderate REF: 20.3 OBJ: 20.3b Describe the relationships between host and bacteria that contribute to the pathogenesis of respiratory tract infections.

MSC: Understanding 28. Some strains of the bacteria Haemophilus influenzae produce a beta-lactamase enzyme that a. confers antibiotic resistance to the bacteria. b. allows attachment of the bacteria to cilia on host cells. c. prevents immunity from forming in the host. d. prevents lysosomes from fusing to phagosomes.

ANS: A DIF: Moderate REF: 20.3 OBJ: 20.3b Describe the relationships between host and bacteria that contribute to the pathogenesis of respiratory tract infections.

MSC: Understanding 29. The differential diagnosis for a patient presenting with a fever and productive cough with bloody sputum would likely include a. tuberculosis and legionellosis. b. walking pneumonia and Pseudomonas pneumonia. c. inhalation anthrax and diphtheria. d. whooping cough and tuberculosis.

ANS: A

DIF: Difficult

REF: 20.3

OBJ: 20.3c Compare and contrast clinical presentations of bacterial infections of the respiratory tract.

MSC: Analyzing 30. A young boy with a sore throat, cervical lymphadenopathy, and a low-grade fever is seen by his physician. Upon examination, his physician notes a thick, grayish membrane covering the boy’s tonsils and soft palate that bleeds when scraped. A bacterial culture will most likely reveal the presence of a. Corynebacterium diphtheriae. c. Moraxella catarrhalis. b. Streptococcus pneumoniae. d. Bordetella pertussis.

ANS: A DIF: Moderate REF: 20.3 OBJ: 20.3c Compare and contrast clinical presentations of bacterial infections of the respiratory tract.

MSC: Analyzing 31. The graph below shows the incidence of whooping cough in the United States. What information can be determined from this graph?

a. Approximately 40,000 individuals were infected with whooping cough in 2007. b. The incidence of whooping cough in infants under one year of age in 2013 was higher than the incidence in 2012. c. Vaccination against whooping cough has become less effective in infants under the age of one year. d. The incidence of whooping cough declined dramatically between 2005 and 2007.

ANS: D DIF: Moderate REF: 20.3 OBJ: 20.3d Develop a prevention plan for different bacterial respiratory pathogens.

MSC: Analyzing 32. The graph below shows the incidence of whooping cough in the United States. What information can be determined from this graph?

a. There was a decline in vaccination rates of infants under one year of age during the early 1990s. b. The incidence of whooping cough in infants under one year of age was declining prior to 1990. c. Waning immunity in adult populations has led to an increase in whooping cough. d. The incidence of whooping cough in infants under one year of age was higher in 2010 than it was in 1995.

ANS: D DIF: Moderate REF: 20.3 OBJ: 20.3d Develop a prevention plan for different bacterial respiratory pathogens.

MSC: Analyzing 33. The figure below shows the relative incidence of pneumonia caused by various microorganisms.

Vaccines are available to prevent

a. b. c. d.

all of the bacterial forms of pneumonia. the most common and least common bacterial causes of pneumonia. viral forms of pneumonia. the form of pneumonia that occurs most frequently in the elderly.

ANS: D DIF: Difficult REF: 20.3 OBJ: 20.3d Develop a prevention plan for different bacterial respiratory pathogens.

MSC: Applying

34. A young man who enjoys spelunking, the recreational sport of exploring caves, develops a flu-like pulmonary illness along with erythema nodosum and arthralgia. The most likely fungal infection in this man is a. histoplasmosis. c. cryptococcosis. b. coccidioidomycosis. d. blastomycosis.

ANS: A DIF: Moderate REF: 20.4 OBJ: 20.4a Identify the most common etiologies of fungal lower respiratory tract infections.

MSC: Analyzing 35. An AIDS patient with a fungal infection develops meningoencephalitis, which is the most prevalent form of a. histoplasmosis. c. cryptococcosis. b. coccidioidomycosis. d. blastomycosis.

ANS: C DIF: Easy REF: 20.4 OBJ: 20.4a Identify the most common etiologies of fungal lower respiratory tract infections.

MSC: Remembering 36. The Ghon complex shown in the figure below is indicative of infection by

a. Mycobacterium tuberculosis. b. Bacillus anthracis.

c. Blastomyces dermatitidis. d. Coccidioides immitis.

ANS: A DIF: Difficult REF: 20.4 OBJ: 20.4b Describe the differences between fungal and bacterial lower respiratory tract infections.

MSC: Analyzing 37. A patient with a respiratory infection who is unresponsive to treatment with antibiotics, lacks a clearly defined presentation, and has seemingly unrelated symptoms a. is more likely to be infected by a fungus than a virus or bacteria. b. is more likely to be infected by a virus than a fungus or bacteria. c. is most likely carrying an antibiotic-resistant form of bacteria. d. would likely have a positive TB skin test.

ANS: A DIF: Moderate REF: 20.4 OBJ: 20.4b Describe the differences between fungal and bacterial lower respiratory tract infections.

MSC: Understanding 38. The most prevalent form of cryptococcosis is found in a. young children. c. the elderly.

b. AIDS patients.

d. adolescents.

ANS: B DIF: Easy REF: 20.4 OBJ: 20.4c Name the risk factors associated with fungal respiratory tract infections.

MSC: Remembering 39. Close contact with respiratory droplets from an individual with ________ is LEAST likely to cause disease. a. histoplasmosis c. pertussis b. influenza d. tuberculosis ANS: A DIF: Easy REF: 20.4 OBJ: 20.4c Name the risk factors associated with fungal respiratory tract infections.

MSC: Applying 40. Close contact with respiratory droplets from an individual with ________ is MOST likely to cause disease. a. histoplasmosis c. cryptococcosis b. blastomycosis d. tuberculosis ANS: D DIF: Easy REF: 20.4 OBJ: 20.4c Name the risk factors associated with fungal respiratory tract infections.

MSC: Applying 41. The diffuse infiltrate shown in the figure below is indicative of

a. pertussis. b. blastomycosis.

c. tuberculosis. d. pneumococcal pneumonia.

ANS: B DIF: Moderate REF: 20.4 OBJ: 20.4c Name the risk factors associated with fungal respiratory tract infections.

MSC: Understanding 42. CASE HISTORY

Jacob, a rambunctious five-year-old boy brought to the clinic by his mother, was complaining of a scratchy sore throat, a nonproductive cough (a cough that does not produce sputum), rhinorrhea (a runny nose), nasal congestion (a stopped-up nose), and a headache that started the night before. He did not have a fever. His complete blood count (CBC)—the number of platelets and red and white blood cells in blood, along with its differential (the different types of red and white blood cells)—was normal, as was his chest X-ray. Jacob was diagnosed with the common cold and was advised to rest, drink plenty of clear liquids, and use over-the-counter cough suppressants and either ibuprofen or acetaminophen for pain.

Based on the symptoms described and what you know about this pathogen, Jacob’s infection can be best described as a ________ respiratory illness. a. viral lower c. bacterial lower b. viral upper d. bacterial upper ANS: B DIF: Easy REF: Case History 20.1 OBJ: 20.2a Compare and contrast the signs and symptoms of upper and lower respiratory tract infections.

MSC: Applying COMPLETION 1. The lowest structure in the respiratory tract, used to produce sounds, is called the ________.

ANS: larynx DIF: Easy REF: 20.1 OBJ: 20.1a List the anatomical differences between the upper and lower respiratory tracts.

MSC: Remembering 2. The ciliated epithelium in the respiratory tract that traps inhaled particles and microorganisms is referred to as the ________.

ANS: mucociliary escalator; mucociliary elevator DIF: Easy REF: 20.1 OBJ: 20.1c Explain the role of the mucociliary elevator in respiratory infection processes.

MSC: Remembering 3. Viruses that cause the common cold may also spread to the sinuses to cause ________.

ANS: sinusitis DIF: Easy REF: 20.2 OBJ: 20.2d Identify the etiology of the major viral respiratory infections based on their presentation.

MSC: Understanding 4. Moraxella catarrhalis may cause bacterial ________.

ANS: sinusitis DIF: Easy REF: 20.3 OBJ: 20.3a List the bacterial etiologies of respiratory tract diseases and the disease’s anatomical location.

MSC: Applying

5. Streptococcal pharyngitis, or strep throat, may be caused by an exotoxin-producing strain of Streptococcus pyogenes that causes fever and a red rash known as ________.

ANS: scarlet fever DIF: Easy REF: 20.3 OBJ: 20.3b Describe the relationships between host and bacteria that contribute to the pathogenesis of respiratory tract infections.

MSC: Remembering 6. The two bacterial diseases of the respiratory system that are prevented by the DTaP vaccine are ________.

ANS: diphtheria and pertussis; pertussis and diphtheria DIF: Easy REF: 20.3 OBJ: 20.3d Develop a prevention plan for different bacterial respiratory pathogens.

MSC: Analyzing 7. Coccidioidomycosis is endemic in the ________ United States.

ANS: western DIF: Easy REF: 20.4 OBJ: 20.4a Identify the most common etiologies of fungal lower respiratory tract infections.

MSC: Remembering 8. Engaging in recreational or occupational activities that expose an individual to fungal spores in moist soils along the Mississippi or Ohio River valleys increases the risk of developing ________.

ANS: blastomycosis DIF: Easy REF: 20.4 OBJ: 20.4c Name the risk factors associated with fungal respiratory tract infections.

MSC: Understanding SHORT ANSWER 1. Stephanie, a one-year-old girl, frequently develops painful cases of acute otitis media within days of developing viral upper respiratory infections. Explain why viral infections of the upper respiratory tract may lead to acute otitis media.

ANS: Acute otitis media is infection within the middle ear. The Eustachian tube connects the middle ear to the nasal cavity, which allows viruses and bacteria to enter the middle ear. Children are more prone to ear infections because the Eustachian tube is shorter and more horizontal in children than it is in adults.

DIF: Moderate REF: 20.1 OBJ: 20.1b Describe the relationship of eyes, ears, and nose with the upper airways.

MSC: Understanding

2. A young patient arrives in the emergency room with a fever, chills, cough, and chest pains. At this point, would it be more likely for a physician to make a differential diagnosis or a definitive diagnosis?

Explain your reasoning.

ANS: A differential diagnosis listing conditions with similar signs and symptoms would be possible, but more testing would be required for a definitive diagnosis because many respiratory diseases present with fever, chills, cough, and chest pain. A definitive diagnosis confirms the exact etiology of the disease.

DIF: Difficult REF: 20.2 OBJ: 20.2a Compare and contrast the signs and symptoms of upper and lower respiratory tract infections.

MSC: Evaluating 3. Describe how a human infected simultaneously with an avian flu strain and a swine flu strain may cause an influenza pandemic.

ANS: When a single cell is infected with different strains of influenza, antigenic shift may occur. The RNA segments of the different strains may uncoat, mix, and re-sort themselves to form a new hemagglutinin gene. This new form of influenza is able to evade the host immune system and may spread rapidly through human populations that lack immunity to the novel form of influenza.

DIF: Difficult REF: 20.2 OBJ: 20.2b Describe the role of mutations in the genesis of influenza pandemics.

MSC: Applying 4. Explain how the M proteins associated with some strains of Streptococcus pyogenes lead to streptococcal sequelae.

ANS: The M proteins of some strains of Streptococcus pyogenes have antigenic determinants, or epitopes, that are similar to human cardiac or kidney cells. When a human produces antibodies against the S. pyogenes M protein with similar epitopes to human cells, the same antibodies can bind to and damage the human cells in an autoimmune reaction. These reactions can damage the heart (rheumatic fever) or kidney (glomerulonephritis).

DIF: Difficult REF: 20.3 OBJ: 20.3b Describe the relationships between host and bacteria that contribute to the pathogenesis of respiratory tract infections.

MSC: Understanding 5. A patient with a bacterial infection of the respiratory system presents with a fever and cough. What additional information regarding his or her cough would be useful in forming a differential diagnosis?

ANS: A cough is commonly seen with infections of the respiratory system. Information about whether the cough is productive, whether distinctive sounds are made by the cough, and the length of time the patient has had a cough would be useful in forming a differential diagnosis.

DIF: Moderate REF: 20.3 OBJ: 20.3c Compare and contrast clinical presentations of bacterial infections of the respiratory tract.

MSC: Evaluating

6. How do fungal respiratory infections differ from bacterial respiratory infections in their transmission and treatment?

ANS: Fungal infections are acquired from spores in the environment and are not transmitted person to person. Bacterial infections are often transmitted person to person by respiratory droplets. Fungal infections are treated with antifungals. Bacterial infections are treated with antibiotics.

DIF: Moderate REF: 20.4 OBJ: 20.4b Describe the differences between fungal and bacterial lower respiratory tract infections.

MSC: Applying 7. CASE HISTORY Jacob, a rambunctious five-year-old boy brought to the clinic by his mother, was complaining of a scratchy sore throat, a nonproductive cough (a cough that does not produce sputum), rhinorrhea (a runny nose), nasal congestion (a stopped-up nose), and a headache that started the night before. He did not have a fever. His complete blood count (CBC)—the number of platelets and red and white blood cells in blood, along with its differential (the different types of red and white blood cells)—was normal, as was his chest X-ray. Jacob was diagnosed with the common cold and was advised to rest, drink plenty of clear liquids, and use over-the-counter cough suppressants and either ibuprofen or acetaminophen for pain.

Why would prescription of an antibiotic likely do more to harm Jacob than help him recover? Consider how this pathogen enters, leaves, and replicates in cells.

ANS: Viruses lack the distinct prokaryotic cellular features antibiotics use to target bacteria (e.g., peptidoglycan and 30S ribosomal subunits), so they cannot be treated by antibiotics. Unnecessary use of antibiotics promotes resistance in the normal flora.

DIF: Moderate REF: Case History 20.1 OBJ: 20.3b Describe the relationships between host and bacteria that contribute to the pathogenesis of respiratory tract infections.

MSC: Applying 8. CASE HISTORY Chloe is a generally healthy two-year-old child who was brought to the clinic by her father. The child had developed a fever the previous night, was irritable, and kept pulling on her left ear. Chloe had also had a runny nose for the previous two weeks. Her temperature was 38.5 C (101.3 F) at the clinic, and the physical exam showed a red and swollen ear, an erythematous ear canal, and a bulging tympanic membrane. Chloe was diagnosed with acute otitis media and prescribed an antibiotic that she had to take for seven days.

If a complete blood count (CBC) was performed on Chloe as a part of her diagnosis, what clues would you expect to see supporting the nature of her infection?

ANS: Elevated WBC counts, especially those associated with bacterial infection.

DIF: Moderate REF: Case History 20.2 OBJ: 20.3c Compare and contrast clinical presentations of bacterial infections of the respiratory tract.

MSC: Applying

Chapter 21: Systemic Infections LEARNING OBJECTIVES 21.1a List the structural components of the cardiovascular and lymphatic systems and their relationship to one another.

21.1b Compare and contrast the systemic and pulmonary circulations.

21.1c Explain the relationship between the circulatory systems and systemic infections.

21.2a Explain the pathogenesis of each systemic viral infection discussed.

21.2b Relate the diagnoses of systemic viral infections to the pathogenesis of the specific virus causing the disease.

21.2c Relate the signs and symptoms of each systemic viral infection with the effect of the respective virus on different organ systems.

21.2d List the treatment and prevention options for different systemic viral infections.

21.3a Compare the systemic signs and symptoms of different bacterial circulatory infections.

21.3b Generate a list of organ malfunctions according to the pathogenesis of each bacterial pathogen discussed.

21.3c Relate the symptoms of the systemic bacterial infections discussed with the progression of each disease.

21.3d Summarize the treatment and prevention plans for the various systemic bacterial infections discussed.

21.4a Name and define the different manifestations of bacterial infections of the heart.

21.4b Compare and contrast different types of endocarditis.

21.4c Discuss the possible links between bacterial infections and atherosclerosis.

21.5a Construct a list of systemic parasitic infections according to the type and mode of transmission of each parasite.

21.5b Relate the different stages of systemic parasitic diseases to the growth cycle of the infecting agent.

21.5c List the organ systems affected by each systemic parasitic infection discussed.

21.5d Devise a plan for prevention of each systemic parasitic infection discussed.

MULTIPLE CHOICE 1. In the figure below, the heart chamber that pumps blood into the systemic circuit is the chamber labeled

a. A. b. B.

c. C. d. D.

ANS: D DIF: Moderate REF: 21.1 OBJ: 21.1a List the structural components of the cardiovascular and lymphatic systems and their

relationship to one another.

MSC: Applying

2. In the figure below, the heart chamber that pumps blood into the pulmonary circuit is the chamber labeled

a. A. b. B.

c. C. d. D.

ANS: B DIF: Moderate REF: 21.1 OBJ: 21.1a List the structural components of the cardiovascular and lymphatic systems and their relationship to one another.

MSC: Applying 3. In the figure below, the heart chambers that receive blood returning to the heart are labeled

a. A and B. b. B and C.

c. C and A. d. D and B.

ANS: C DIF: Moderate REF: 21.1 OBJ: 21.1a List the structural components of the cardiovascular and lymphatic systems and their relationship to one another.

MSC: Applying 4. The figure below shows blood vessels. If lymphatic capillaries were to be added to this figure, they would be most closely associated with

a. A. b. B.

c. C. d. D.

ANS: A DIF: Moderate REF: 21.1 OBJ: 21.1a List the structural components of the cardiovascular and lymphatic systems and their relationship to one another.

MSC: Applying 5. Which of the following statements is an accurate comparison between the cardiovascular and lymphatic systems? a. The lymphatic system contains a pump that generates high pressures. b. The lymphatic system is used to transport nutrients and oxygen to body cells. c. The cardiovascular system carries lymph through lymph nodes. d. The cardiovascular system is composed of a pulmonary circuit and a systemic circuit.

ANS: D DIF: Easy REF: 21.1 OBJ: 21.1a List the structural components of the cardiovascular and lymphatic systems and their relationship to one another.

MSC: Understanding 6. The circuit shown below

a. carries oxygenated blood to body cells. b. removes waste from body cells.

c. replenishes oxygen in blood. d. replenishes carbon dioxide in blood.

ANS: C DIF: Easy REF: 21.1 OBJ: 21.1b Compare and contrast the systemic and pulmonary circulations.

MSC: Understanding 7. Pulmonary arteries carry ________ blood toward the ________. a. oxygenated; heart c. oxygenated; lungs b. deoxygenated; heart d. deoxygenated; lungs ANS: D DIF: Easy REF: 21.1 OBJ: 21.1b Compare and contrast the systemic and pulmonary circulations.

MSC: Remembering 8. Margo, a nursing home resident, experiences a scratch on her leg that becomes infected by Staphylococcus. During a shower a nursing assistant notices a red streak extending from the skin infection and alerts a nurse. What term describes this red streak? a. lymphadenopathy c. lymphangitis b. lymphadenitis d. endocarditis ANS: C DIF: Easy REF: 21.1 OBJ: 21.1c Explain the relationship between the circulatory systems and systemic infections.

MSC: Understanding 9. The cells infected by cytomegalovirus (CMV) include a. fibroblasts. c. lymphocytes.

b. osteocytes.

d. neurons.

ANS: C DIF: Moderate REF: 21.1 OBJ: 21.2b Relate the diagnoses of systemic viral infections to the pathogenesis of the specific virus causing the disease.

MSC: Remembering 10. What causes lymphadenitis in a patient with an Epstein-Barr virus infection? a. proliferation of B and T cells b. removal of abnormal blood cells from circulation c. infection of epithelial cells within lymph nodes d. production of heterophile antibodies ANS: A DIF: Moderate REF: 21.2 OBJ: 21.2b Relate the diagnoses of systemic viral infections to the pathogenesis of the specific virus causing the disease.

MSC: Applying 11. Why does dissemination of Epstein-Barr virus (EBV) often lead to hepatomegaly and splenomegaly? a. EBV produces abnormal blood cells that are removed by the liver and spleen. b. Latent EBV within the liver and spleen causes enlargement of these organs. c. The cells infected by EBV are only found in the liver and spleen. d. EBV-infected B cells travel throughout the body and then reside within the liver and spleen.

ANS: A DIF: Difficult REF: 21.1 OBJ: 21.2c Relate the signs and symptoms of each systemic viral infection with the effect of the respective virus on different organ systems.

MSC: Analyzing 12. The most common treatment for systemic viral diseases is a. the treatment of symptoms. c. immunotherapy. b. antiviral medications. d. antibiotics.

ANS: A DIF: Moderate REF: 21.2 OBJ: 21.2d List the treatment and prevention options for different systemic viral infections.

MSC: Applying 13. Which of the following procedures would most directly limit transmission of arboviruses such as dengue viruses? a. eliminate mosquitoes b. prevent contact with infected saliva c. prevent contact with infected fecal matter d. eliminate rodents ANS: A DIF: Easy REF: 21.2 OBJ: 21.2d List the treatment and prevention options for different systemic viral infections.

MSC: Analyzing 14. What treatment is typically used for otherwise healthy individuals who contract infectious mononucleosis? a. hospitalization c. activity restriction b. antiviral therapy d. passive immunization ANS: C DIF: Easy REF: 21.2 OBJ: 21.2d List the treatment and prevention options for different systemic viral infections.

MSC: Remembering 15. Two major systemic bacterial diseases associated with septicemia are

a. vibriosis and Lyme disease. b. typhoid fever and salmonellosis.

c. tularemia and leptospirosis. d. brucellosis and epidemic typhus.

ANS: B DIF: Moderate REF: 21.3 OBJ: 21.3a Compare the systemic signs and symptoms of different bacterial circulatory infections.

MSC: Applying 16. The spirochete bacterial disease that leads to complications including arthritis and heart rhythm abnormalities and is transmitted by deer ticks is known as a. Lyme disease. c. tularemia. b. brucellosis. d. bubonic plague.

ANS: A DIF: Easy REF: 21.3 OBJ: 21.3a Compare the systemic signs and symptoms of different bacterial circulatory infections.

MSC: Applying 17. As a teenager, Angelica developed a systemic bacterial infection. The bacteria, found on some lettuce in a restaurant salad, killed several other people. In Angelica, the bacteria invaded her tissue macrophages, traveled throughout her bloodstream, and infected her gallbladder in addition to infecting her liver, spleen, and kidney. She survived but remained a chronic carrier of a. Brucella abortis. c. Rickettsia prowazekii. b. Yersinia pestis. d. Salmonella enterica servovar Typhi.

ANS: D DIF: Difficult REF: 21.3 OBJ: 21.3b Generate a list of organ malfunctions according to the pathogenesis of each bacterial pathogen discussed.

MSC: Evaluating 18. Borrelia burgdorferi produces an enzyme that cleaves proteoglycans. This enzyme mainly affects ________ tissue. a. epithelial c. muscle b. connective d. nervous ANS: B DIF: Difficult REF: 21.3 OBJ: 21.3b Generate a list of organ malfunctions according to the pathogenesis of each bacterial pathogen discussed.

MSC: Understanding 19. When Yersinia pestis remains untreated in a human body, it can enter the bloodstream and ultimately invade the a. liver. c. spleen. b. kidneys. d. lungs.

ANS: D DIF: Moderate REF: 21.3 OBJ: 21.3c Relate the symptoms of the systemic bacterial infections discussed with the progression of each disease.

MSC: Applying 20. Rickettsioses, such as Rocky Mountain spotted fever, cause systemic symptoms because Rickettsia species a. are obligate intracellular bacteria that infect endothelial cells throughout the body. b. are phagocytized by macrophages and travel throughout the blood within macrophages. c. infect lymphocytes and use the lymphatic system to move throughout the body. d. infect fibroblasts within connective tissues and use the reticuloendothelial system to move throughout the body.

ANS: A DIF: Difficult REF: 21.3 OBJ: 21.3c Relate the symptoms of the systemic bacterial infections discussed with the progression of each disease.

MSC: Applying

21. The antibiotic most commonly used to treat the major systemic bacterial infections is a. penicillin. c. ceftriaxone. b. fluoroquinolones. d. tetracycline.

ANS: D DIF: Moderate REF: 21.3 OBJ: 21.3d Summarize the treatment and prevention plans for the various systemic bacterial infections discussed.

MSC: Analyzing 22. A human vaccine is available to prevent a. bubonic plague. b. salmonellosis.

c. typhoid fever. d. Lyme disease.

ANS: C DIF: Moderate REF: 21.3 OBJ: 21.3d Summarize the treatment and prevention plans for the various systemic bacterial infections discussed.

MSC: Remembering 23. Which of the structures indicated on the figure below of the heart wall is most frequently affected during a bacterial cardiac infection?

a. A b. B

c. C d. D

ANS: A DIF: Easy REF: 21.4 OBJ: 21.4a Name and define the different manifestations of bacterial infections of the heart.

MSC: Applying 24. Bacterial endocarditis affects the a. thinner lining of the heart. b. muscle of the heart. c. sac surrounding the heart. d. lining of blood vessels exiting the heart.

ANS: A DIF: Easy REF: 21.4 OBJ: 21.4a Name and define the different manifestations of bacterial infections of the heart.

MSC: Understanding 25. Acute bacterial endocarditis is often caused by a. Streptococcus mutans. c. Chlamydophila pneumoniae. b. Staphylococcus aureus. d. Porphyromonas gingivalis.

ANS: B DIF: Moderate REF: 21.4 OBJ: 21.4b Compare and contrast different types of endocarditis.

MSC: Understanding

26. Subacute bacterial endocarditis is often caused by a. Streptococcus mutans. c. Chlamydophila pneumoniae. b. Staphylococcus aureus. d. Porphyromonas gingivalis.

ANS: A DIF: Moderate REF: 21.4 OBJ: 21.4b Compare and contrast different types of endocarditis.

MSC: Understanding 27. Atherosclerosis is associated with infection of a. endothelial cells. c. macrophages. b. mast cells. d. lymphocytes.

ANS: C DIF: Easy REF: 21.4 OBJ: 21.4c Discuss the possible links between bacterial infections and atherosclerosis.

MSC: Understanding 28. Which periodontal pathogen has been found within atherosclerotic plaques? a. Streptococcus mutans c. Chlamydophila pneumoniae b. Staphylococcus aureus d. Porphyromonas gingivalis ANS: D DIF: Moderate REF: 21.4 OBJ: 21.4c Discuss the possible links between bacterial infections and atherosclerosis.

MSC: Remembering 29. Which of the following diseases is caused by a helminth? a. toxoplasmosis c. leishmaniasis b. babesiosis d. schistosomiasis ANS: D DIF: Easy REF: 21.5 OBJ: 21.5a Construct a list of systemic parasitic infections according to the type and mode of transmission of each parasite.

MSC: Applying 30. Which of the following pairs of diseases are transmitted by mosquitoes? a. malaria and toxoplasmosis c. leishmaniasis and schistosomiasis b. babesiosis and Chagas’ disease d. lymphatic filariasis and malaria ANS: D DIF: Moderate REF: 21.5 OBJ: 21.5a Construct a list of systemic parasitic infections according to the type and mode of transmission of each parasite.

MSC: Analyzing 31. The map below shows areas where malaria is endemic. What organism is endemic to the same regions?

a. Anopheles mosquitoes

c. reduviid bugs

b. Ixodes scapularis ticks

d. sand flies

ANS: A DIF: Moderate REF: 21.5 OBJ: 21.5a Construct a list of systemic parasitic infections according to the type and mode of transmission of each parasite.

MSC: Analyzing 32. What role does stomach acidity play in a toxoplasmosis infection? a. It converts bradyzoites into cyst forms for release from the body. b. It causes the release of spores within the definitive host. c. It allows the release of spores within the intermediate host. d. It allows gametes to form from spores within the intermediate host.

ANS: C DIF: Difficult REF: 21.5 OBJ: 21.5b Relate the different stages of systemic parasitic diseases to the growth cycle of the infecting agent.

MSC: Applying 33. The rapidly dividing protozoan cells that circulate throughout the body during a toxoplasmosis infection are called a. promastigotes. c. bradyzoites. b. tachyzoites. d. asmastigotes.

ANS: A DIF: Moderate REF: 21.5 OBJ: 21.5b Relate the different stages of systemic parasitic diseases to the growth cycle of the infecting agent.

MSC: Understanding 34. What causes symptoms of malaria to occur every 48–72 hours? a. The life span of sporozoites is approximately 48–72 hours. b. The liver releases merozoites every 48–72 hours. c. Sporozoites are converted into merozoites during a 48–72-hour cycle. d. Release of merozoites and red cell debris is synchronized.

ANS: D DIF: Difficult REF: 21.5 OBJ: 21.5b Relate the different stages of systemic parasitic diseases to the growth cycle of the infecting agent.

MSC: Applying 35. Sand flies carry a motile form of a a. promastigote. b. merozoite.

c. bradyzoite. d. asmastigote.

ANS: A DIF: Moderate REF: 21.5 OBJ: 21.5b Relate the different stages of systemic parasitic diseases to the growth cycle of the infecting agent.

MSC: Remembering 36. The protozoan infection that may be transmitted from mother to fetus and cause fetal infection leading to mental retardation, neurological abnormalities, and microcephaly is a. visceral leishmaniasis. c. schistosomiasis. b. toxoplasmosis. d. Chagas’ disease.

ANS: B DIF: Moderate REF: 21.5 OBJ: 21.5c List the organ systems affected by each systemic parasitic infection discussed.

MSC: Understanding 37. The swelling seen in the individual’s leg shown in the figure below is indicative of

a. cutaneous leishmaniasis. b. lymphatic filariasis.

c. babesiosis. d. Chagas’ disease.

ANS: B DIF: Moderate REF: 21.5 OBJ: 21.5c List the organ systems affected by each systemic parasitic infection discussed.

MSC: Understanding 38. To prevent infection of a fetus would require successful treatment of a mother infected with a. toxoplasmosis. c. schistosomiasis. b. babesiosis. d. leishmaniasis.

ANS: A DIF: Moderate REF: 21.5 OBJ: 21.5d Devise a plan for prevention of each systemic parasitic infection discussed.

MSC: Applying 39. Individuals living in the northeastern United States should take precautions to prevent tick bites to avoid the emerging protozoan disease that grows inside red blood cells. This disease is known as a. Lyme disease. c. Chagas’ disease. b. babesiosis. d. malaria.

ANS: B DIF: Moderate REF: 21.5 OBJ: 21.5d Devise a plan for prevention of each systemic parasitic infection discussed.

MSC: Analyzing 40. During her pregnancy, Marcia’s obstetrician recommended she have her husband clean the cat litter box. Avoiding contact with contaminated cat feces during a pregnancy is important in preventing a. toxoplasmosis. c. schistosomiasis. b. babesiosis. d. leishmaniasis.

ANS: A DIF: Moderate REF: 21.5 OBJ: 21.5d Devise a plan for prevention of each systemic parasitic infection discussed.

MSC: Analyzing 41. CASE HISTORY

Brad, a nine-year-old from Connecticut, developed a fever and a large (8 cm) reddish rash with a clear center (erythema migrans) on his arm. He also had some left-side facial nerve palsy. Brad had returned a week earlier from a Boy Scout camping trip to the local woods, where he did a lot of hiking.

When asked by his physician, Brad admitted to finding a tick on his stomach while in the woods but thought little of it. The doctor ordered serological tests for Borrelia burgdorferi (the organism that causes Lyme disease), Rickettsia rickettsii (which produces Rocky Mountain spotted fever), and Anaplasma phagocytophilum (which causes ehrlichiosis). The ELISA for B. burgdorferi came back positive, confirming a diagnosis of Lyme disease. The boy was given a three-week regimen of doxycycline (a tetracycline derivative), which led to resolution of the rash and palsy.

Which is true of B. burgdorferi? a. It is commonly transmitted via the bite of the deer tick, but may also be transmitted by rabbits, rodents, and mosquitoes. b. B. burgdorferi spreads throughout the body due to enzymes that target host connective tissues and ligaments. c. B. burgdorferi is easily detected via Gram staining a blood smear. d. Most people naturally clear Lyme infection without treatment ANS: B DIF: Moderate REF: Case History 21.2 OBJ: 21.3c Relate the symptoms of the systemic bacterial infections discussed with the progression of each disease.

MSC: Understanding COMPLETION 1. The large vessels that carry blood away from the heart are called ________.

ANS: arteries DIF: Easy REF: 21.1 OBJ: 21.1a List the structural components of the cardiovascular and lymphatic systems and their relationship to one another.

MSC: Remembering 2. The blood vessels returning oxygenated blood to the heart are the ________.

ANS: pulmonary veins; pulmonary vein DIF: Easy REF: 21.1 OBJ: 21.1b Compare and contrast the systemic and pulmonary circulations.

MSC: Remembering 3. Giant cells with the appearance of “owl’s eyes” are indicative of a(n) ________ infection.

ANS: cytomegalovirus; CMV DIF: Easy REF: 21.1 OBJ: 21.2c Relate the signs and symptoms of each systemic viral infection with the effect of the respective virus on different organ systems.

MSC: Understanding 4. When traveling to tropical and subtropical areas where Aedes aegypti mosquitoes are endemic, U.S. citizens could receive a vaccine to prevent ________.

ANS: yellow fever; jungle yellow fever DIF: Moderate

REF: 21.2

OBJ: 21.2d List the treatment and prevention options for different systemic viral infections.

MSC: Applying 5. The bipolar staining seen in the small bacteria cells in the slide shown below indicates the presence of ________.

ANS: Yersinia pestis DIF: Moderate REF: 21.3 OBJ: 21.3a Compare the systemic signs and symptoms of different bacterial circulatory infections.

MSC: Applying 6. The cycle of plague shown below is capable of directly initiating the development of enlarged nodes called ________ in a human.

ANS: buboes DIF: Easy REF: 21.3 OBJ: 21.3c Relate the symptoms of the systemic bacterial infections discussed with the progression of each disease.

MSC: Understanding 7. Drugs used to treat the major systemic bacterial diseases fall into the category of ________.

ANS: antibiotics; antibiotic DIF: Easy REF: 21.3 OBJ: 21.3d Summarize the treatment and prevention plans for the various systemic bacterial infections discussed.

MSC: Understanding 8. Inflammation of the inner layer of the heart is referred to as ________.

ANS: endocarditis DIF: Easy REF: 21.4 OBJ: 21.4a Name and define the different manifestations of bacterial infections of the heart.

MSC: Remembering 9. Inflammation of the sac covering the heart is defined as ________.

ANS: pericarditis DIF: Easy REF: 21.4 OBJ: 21.4a Name and define the different manifestations of bacterial infections of the heart.

MSC: Remembering 10. Bacterial endocarditis that has a slow onset and presents with vague symptoms such as fatigue, intermittent fevers, and headaches is called ________.

ANS: subacute bacterial endocarditis; SBE DIF: Easy REF: 21.4 OBJ: 21.4b Compare and contrast different types of endocarditis.

MSC: Remembering 11. Drinking water contaminated with the free-living infectious form of a helminth may lead to complications such as dermatitis, cellulitis, or lymphangitis in the disease ________.

ANS: schistosomiasis DIF: Moderate REF: 21.5 OBJ: 21.5a Construct a list of systemic parasitic infections according to the type and mode of transmission of each parasite.

MSC: Applying 12. The definitive host in the life cycle of lymphatic filariasis is a ________.

ANS: human DIF: Easy REF: 21.5 OBJ: 21.5b Relate the different stages of systemic parasitic diseases to the growth cycle of the infecting agent.

MSC: Understanding 13. The asexual cycle of plasmodium within humans occurs within the ________ system.

ANS: circulatory; cardiovascular DIF: Moderate REF: 21.5 OBJ: 21.5c List the organ systems affected by each systemic parasitic infection discussed.

MSC: Understanding 14. Preventing leishmaniasis would require preventing bites from ________.

ANS: sand flies DIF: Easy REF: 21.5 OBJ: 21.5d Devise a plan for prevention of each systemic parasitic infection discussed.

MSC: Understanding 15. The herpes virus that initially infects the oropharyngeal epithelium, tonsils, and salivary glands, and is associated with endemic Burkitt’s lymphoma, is known as ________.

ANS: Epstein-Barr virus; EBV DIF: Easy REF: 21.2 OBJ: 21.2b Relate the diagnoses of systemic viral infections to the pathogenesis of the specific virus causing the disease.

MSC: Remembering SHORT ANSWER 1. Carlos is experiencing a systemic infection caused by a bacterium in the genus Leptospira. The signs and symptoms associated with his illness are fever, general malaise, muscle aches, abdominal pain, and jaundice. Explain the role his circulatory and lymphatic systems played in the development of the signs and symptoms he is experiencing.

ANS: The circulatory system carries blood to all tissues and organs of the body, and the lymphatic system ultimately empties into the circulatory system. Bacteria and other infectious agents that are able to infiltrate the circulatory or lymphatic system and enter the bloodstream are able to travel throughout the body. Systemic infections often have flu-like symptoms accompanied by organ-specific manifestations depending on the tissues and organs involved.

DIF: Difficult REF: 21.1 OBJ: 21.1c Explain the relationship between the circulatory systems and systemic infections.

MSC: Applying 2. Explain how the pathogenesis of Epstein-Barr virus (EBV) leads to the presence of heterophile antibodies in the patient’s blood.

ANS: EBV infects B cells. EBV-infected B cells are nonspecifically stimulated to proliferate and differentiate into antibody-producing plasma cells. The antibodies secreted by the plasma cells are the antibodies their B-cell progenitors were programmed to produce and include nonspecific heterophile antibodies indicative of an EBV infection that react against horse and sheep red blood cells.

DIF: Difficult REF: 21.1 OBJ: 21.2a Explain the pathogenesis of each systemic viral infection discussed.

MSC: Applying 3. Describe similarities and differences between bubonic plague and secondary plague pneumonia.

ANS: Bubonic plague and secondary plague pneumonia are both caused by the bacterium Yersinia pestis.

Bubonic plague occurs when infected fleas bite a human and regurgitate Yersinia pestis into the bite wound. When the bacteria move into lymph nodes, characteristic buboes form. If the organism invades the lungs, the individual is said to have secondary pneumonic plague, which is spread person to person through aerosol droplets. Secondary plague pneumonia is more dangerous because it can lead to death within 24–48 hours and is spread rapidly by aerosol droplets.

DIF: Difficult REF: 21.3 OBJ: 21.3b Generate a list of organ malfunctions according to the pathogenesis of each bacterial pathogen discussed.

MSC: Evaluating 4. Explain how Chlamydophila pneumoniae may play a role in the development of atherosclerosis.

ANS: Chlamydophila pneumoniae infects alveolar macrophages and leads to “activated” macrophages circulating through blood vessels. These activated macrophages generate an inflammatory response that lowers HDL levels and increases clotting. Overall, the inflammatory response damages endothelial cells and leads to the formation of plaques.

DIF: Difficult REF: 21.4 OBJ: 21.4c Discuss the possible links between bacterial infections and atherosclerosis.

MSC: Analyzing 5. Malaria is caused by four species of Plasmodium. There are two distinct stages of a malarial infection, an asexual cycle and a sexual cycle. Summarize the key stages in the development and transmission of a malarial infection.

ANS: The erythrocytic phase is the asexual part of the cycle. The mosquito injects Plasmodium into the bloodstream upon taking a blood meal. The haploid sporozoites are injected and travel to the liver, where they undergo asexual fission to produce merozoites. The merozoites then infect a red blood cell.

The red blood cell eventually lyses, releasing haploid merozoites that infect more red blood cells.

Some of the merozoites develop into male and female gametocytes. These gametocytes are taken in by a mosquito during a blood meal. During the sexual part of the life cycle, the male and female gametocytes fuse in the midgut of the mosquito, producing zygotes. The zygotes produce sporozoites that will ultimately be injected into a human host, starting the erythrocytic phase again.

DIF: Moderate REF: 21.5 OBJ: 21.5b Relate the different stages of systemic parasitic diseasees to the growth cycle of the infecting agent.

MSC: Remembering 6. CASE HISTORY Brad, a nine-year-old from Connecticut, developed a fever and a large (8 cm) reddish rash with a clear center (erythema migrans) on his arm. He also had some left-side facial nerve palsy. Brad had returned a week earlier from a Boy Scout camping trip to the local woods, where he did a lot of hiking.

When asked by his physician, Brad admitted to finding a tick on his stomach while in the woods but thought little of it. The doctor ordered serological tests for Borrelia burgdorferi (the organism that causes Lyme disease), Rickettsia rickettsii (which produces Rocky Mountain spotted fever), and Anaplasma phagocytophilum (which causes ehrlichiosis). The ELISA for B. burgdorferi came back positive, confirming a diagnosis of Lyme disease. The boy was given a three-week regimen of doxycycline (a tetracycline derivative), which led to resolution of the rash and palsy.

Would treatment or prevention of future infection have differed for either of the two pathogens not involved in this particular infection, Rickettsia rickettsia and Anaplasma phagocytophilum? What is a major difference between these pathogens and B. burgdorferi?

ANS: Treatment and prevention are largely similar. None has a vaccine, all are tick transmitted, and all are potentially treatable by doxycycline (instructors may choose to accept the answer “broad spectrum ribosome-targeting antibiotics”); however, B. burgdorferi is the only extracellular pathogen in the group.

DIF: Difficult REF: Case History 21.2 OBJ: 21.3d Summarize the treatment and prevention plans for the various systemic bacterial infections discussed.

MSC: Remembering 7. CASE HISTORY Elizabeth was 58 years old and had a history of mitral valve prolapse (a common congenital condition in which a heart valve does not close properly). She was on immunosuppressive therapy following a kidney transplant. She had recently been admitted to the hospital complaining of fatigue, intermittent fevers for five weeks, and headaches for three weeks—symptoms the physician recognized as possible indications of endocarditis. Elizabeth reported having a dental procedure a few weeks prior to the onset of symptoms but forgot to take antibiotics beforehand. A sample of her blood placed in a liquid bacteriological medium grew Gram-positive cocci, which turned out to be Streptococcus mutans, a bacterial species associated with dental caries. With the finding of bacteria in the bloodstream, the diagnosis of bacterial endocarditis was confirmed. Elizabeth began a one-month course of intravenous penicillin G and gentamicin therapy and eventually recovered to normal health.

Elizabeth presented with symptoms of subacute bacterial endocarditis. How would the presentation differ for the acute form of the disease? What other differences distinguish the two?

ANS: Students should primarily discuss the difference in signs, symptoms, timeline, and type of organism involved, as well as potential patient risk factors.

Subacute bacterial endocarditis (SBE) has a slow onset with vague symptoms. It is usually caused by a bacterial infection of a heart valve. Subacute bacterial endocarditis infections are usually (but not always) caused by a viridans streptococcus from the oral microbiota (for example, Streptococcus mutans, a common cause of dental caries). Viridans streptococci is a general term for normal microbiota streptococci whose colonies produce green alpha hemolysis on blood agar (viridans, from the Greek viridis, “to be green”). Most patients who develop infective endocarditis have mitral valve prolapse (90%), although this is frequently not the case when patients are intravenous drug abusers or have hospital-acquired (nosocomial) infections.

When virulent organisms, such as Staphylococcus aureus, gain access to cardiac tissue, a rapidly progressive and highly destructive infection ensues: acute bacterial endocarditis (ABE).

Symptoms of acute endocarditis include fever, pronounced valvular regurgitation (backflow of blood through the valve), and abscess formation. Most patients with subacute bacterial endocarditis present with a fever that lasts several weeks. They also complain of nonspecific symptoms, such as cough, shortness of breath, joint pain, diarrhea, and abdominal or flank pain. Endocarditis is suspected in any patient who has a heart murmur and an unexplained fever for at least one week. Sharing needles or using a contaminated needle can introduce bacteria directly into the bloodstream, so subacute bacterial endocarditis should be considered in any intravenous drug user who has a fever, even in the absence of a heart murmur.

DIF: Moderate REF: Case History 21.3 OBJ: 21.4b Compare and contrast different types of endocarditis.

MSC: Analyzing

Chapter 22: Infections of the Digestive System LEARNING OBJECTIVES 22.1a List the structural components of the digestive system and describe the relationship between them.

22.1b Name the functions of different structures of the digestive system.

22.1c Explain the roles of specialized cells of the intestinal tract (chief cells, M cells, parietal cells, and mucous neck cells).

22.2a List microbes comprising normal microbiota of the oral cavity.

22.2b Analyze how biofilms contribute to infections of the oral cavity.

22.2c Compare the signs and symptoms of common infections of the oral cavity.

22.2d Explain how oral cavity infections impact diseases elsewhere in the body.

22.3a List the most common signs and symptoms associated with gastrointestinal infections.

22.3b Correlate microbial pathogenic mechanisms with the presenting signs and symptoms of gastrointestinal infections.

22.3c Outline the general mechanisms of diarrhea.

22.4a Match gastrointestinal symptoms to the viral infections that cause them.

22.4b List routes of transmission of specific viral diseases of the gastrointestinal tract.

22.4c Discuss viral pathogenic mechanisms responsible for specific disease signs and symptoms in the gastrointestinal tract.

22.5a Categorize GI infections by bacterial pathogenic mechanisms.

22.5b Correlate bacterial virulence mechanisms to GI disease symptoms.

22.5c Relate the treatment of GI infections to virulence of GI pathogens.

22.5d Evaluate treatment and prevention methods used for bacterial infections of the gastrointestinal tract.

22.6a Distinguish GI infections caused by protozoa from those caused by helminths.

22.6b Describe the role of parasitic life cycles in the transmission and pathogenesis of parasitic GI diseases.

22.6c Generate a list of the diagnostic, prevention, and treatment options available for the parasitic diseases discussed.

MULTIPLE CHOICE 1. Which part of the human digestive tract cannot be colonized by microorganisms? a. mouth b. small intestine c. liver d. All parts of the digestive tract can be colonized.

ANS: D DIF: Moderate REF: 22.1 OBJ: 22.1a List the structural components of the digestive system and describe the relationship between them.

MSC: Understanding 2. The breakdown of food begins a. in the esophagus. b. when saliva is secreted by the salivary glands. c. in the gastric acids of the stomach. d. in the large intestine.

ANS: B

DIF: Easy

REF: 22.1

OBJ: 22.1b Name the functions of different structures of the digestive system.

MSC: Understanding 3. The job of the esophagus is to a. propel food toward the stomach. b. separate the contents of the abdominal cavity from the chest. c. digest food. d. break down toxins.

ANS: A DIF: Easy REF: 22.1 OBJ: 22.1b Name the functions of different structures of the digestive system.

MSC: Remembering 4. What is chyme? a. the wavelike motion of intestinal muscles b. semisolid waste c. food broken down by muscle contraction and gastric juices d. the interior stomach lining ANS: C DIF: Easy REF: 22.1 OBJ: 22.1b Name the functions of different structures of the digestive system.

MSC: Understanding 5. Many enteric pathogens are transmitted through a. sexual contact. c. airborne transmission. b. the parenteral route. d. the fecal-oral route.

ANS: D DIF: Easy REF: 22.1 OBJ: 22.1b Name the functions of different structures of the digestive system.

MSC: Remembering 6. During digestion, bicarbonate is secreted by ________ cells. a. parietal c. mucous neck b. chief d. M ANS: C DIF: Moderate REF: 22.1 OBJ: 22.1c Explain the roles of specialized cells of the intestinal tract (chief cells, M cells, parietal cells, and mucous neck cells).

MSC: Understanding 7. Which of the following is NOT a natural defense of the oral cavity? a. acidic conditions c. IgA b. lysozyme d. digestive mucous ANS: A DIF: Moderate REF: 22.2 OBJ: 22.2a List microbes comprising normal microbiota of the oral cavity.

MSC: Understanding 8. The purpose of drinking fluoride-treated water is that it a. hardens tooth enamel. c. fights plaque. b. softens tooth enamel. d. kills organisms that cause cavities.

ANS: A DIF: Easy REF: 22.2 OBJ: 22.2b Analyze how biofilms contribute to infections of the oral cavity.

MSC: Remembering 9. Which is NOT a common cause of periodontal disease?

a. Aggregatibacter b. Porphyromonas

c. Bacteroides d. Lactobacillus

ANS: D DIF: Moderate REF: 22.2 OBJ: 22.2c Compare the signs and symptoms of common infections of the oral cavity.

MSC: Understanding 10. Individuals with ________ find eating and swallowing to be painful. a. gingivitis c. dental caries b. trench mouth d. plaque ANS: B DIF: Easy REF: 22.2 OBJ: 22.2c Compare the signs and symptoms of common infections of the oral cavity.

MSC: Understanding 11. What is shown in the figure below?

a. a Candida albicans infection b. dental caries

c. strep throat d. a Streptococcus mutans infection

ANS: A DIF: Moderate REF: 22.2 OBJ: 22.2c Compare the signs and symptoms of common infections of the oral cavity.

MSC: Applying 12. When does dental caries become painful? a. when the biofilm forms on the tooth b. when the enamel breaks down

c. when the decay penetrates the nerve d. Dental caries is never painful.

ANS: C DIF: Easy REF: 22.2 OBJ: 22.2c Compare the signs and symptoms of common infections of the oral cavity.

MSC: Understanding 13. The tropism of Salmonella infections includes a. the intestinal lumen. c. Paneth cells. b. the ileum. d. M cells.

ANS: D DIF: Moderate REF: 22.3 OBJ: 22.3a List the most common signs and symptoms associated with gastrointestinal infections.

MSC: Understanding 14. Which type of diarrhea does NOT involve water leaving intestinal cells? a. osmotic c. motility-related b. secretory d. inflammatory ANS: C DIF: Moderate REF: 22.3 OBJ: 22.3b Correlate microbial pathogenic mechanisms with the presenting signs and symptoms of

gastrointestinal infections.

MSC: Understanding

15. Shannon comes down with a Clostridium difficile infection that results in severe colitis. She is experiencing inflammation of the a. small intestine. c. stomach lining. b. large intestine. d. Paneth cells.

ANS: B DIF: Moderate REF: 22.3 OBJ: 22.3b Correlate microbial pathogenic mechanisms with the presenting signs and symptoms of gastrointestinal infections.

MSC: Applying 16. A nondeadly intestinal pathogen will cause watery diarrhea in order to a. leave before the host is irreparably harmed. b. leave before the host immune system becomes activated and begins attacking the pathogen. c. escape to a different organ system. d. flush out the competition.

ANS: B DIF: Moderate REF: 22.3 OBJ: 22.3c Outline the general mechanisms of diarrhea.

MSC: Applying

17. A patient presents at the clinic exhibiting signs of jaundice. How can you confirm that the individual has jaundice? a. urinalysis c. eye exam b. spinal tap d. MRI ANS: A DIF: Difficult REF: 22.3 OBJ: 22.3c Outline the general mechanisms of diarrhea.

MSC: Analyzing

18. Tom has been experiencing hepatitis-like symptoms for seven months. When he finally gets around to going to the doctor, his blood tests positive for HBsAg and IgG antibody to HBsAg. Which of the following is the best diagnosis for Tom? a. acute hepatitis B c. acute hepatitis D b. chronic hepatitis B d. chronic hepatitis D ANS: B DIF: Moderate REF: 22.4 OBJ: 22.4a Match gastrointestinal symptoms to the viral infections that cause them.

MSC: Understanding 19. Even with healthy liver function, the majority of individuals infected with ________ develop a chronic infection. a. rotavirus c. hepatitis B b. hepatitis A d. hepatitis C ANS: D DIF: Moderate REF: 22.4 OBJ: 22.4a Match gastrointestinal symptoms to the viral infections that cause them.

MSC: Understanding 20. Cynthia travels to Honduras and eats raw oysters from a small restaurant out in the middle of nowhere.

After feeling sick for a while, she goes to the clinic when jaundice appears. Cynthia is very concerned that she is going to die. What does the health care worker tell her? a. She should be fine, as the virus causing her condition is self-limited and will be cleared by her immune system. b. She should be fine because she came in quickly and will respond well to antiviral drugs. c. She will need to be hospitalized, but with the right treatment, she will eventually be fine.

d. She has a fatal condition.

ANS: A DIF: Difficult REF: 22.4 OBJ: 22.4b List routes of transmission of specific viral diseases of the gastrointestinal tract.

MSC: Applying 21. Adult infection with ________ can sometimes lead to meningitis. a. rotavirus c. hepatitis A b. mumps virus d. hepatitis D ANS: B DIF: Moderate REF: 22.4 OBJ: 22.4b List routes of transmission of specific viral diseases of the gastrointestinal tract.

MSC: Understanding 22. Viruses that cause vomiting will often produce enterotoxins that result in a. overstimulation of the vagus nerve. c. hypoperistalsis. b. understimulation of the vagus nerve. d. isoperistalsis.

ANS: A DIF: Moderate REF: 22.4 OBJ: 22.4c Discuss viral pathogenic mechanisms responsible for specific disease signs and symptoms in the gastrointestinal tract.

MSC: Understanding 23. Oophoritis can result in ________ infected with mumps. a. prepubescent males c. prepubescent females b. postpubescent males d. postpubescent females ANS: D DIF: Moderate REF: 22.4 OBJ: 22.4c Discuss viral pathogenic mechanisms responsible for specific disease signs and symptoms in the gastrointestinal tract.

MSC: Understanding 24. Orchitis can result in ________ infected with mumps. a. prepubescent males c. prepubescent females b. postpubescent males d. postpubescent females ANS: B DIF: Moderate REF: 22.4 OBJ: 22.4c Discuss viral pathogenic mechanisms responsible for specific disease signs and symptoms in the gastrointestinal tract.

MSC: Understanding 25. Which of the following organisms is noninvasive, yet causes bloody diarrhea? a. Salmonella c. Campylobacter b. Shigella d. enterohemorrhagic E. coli ANS: D DIF: Moderate REF: 22.5 OBJ: 22.5a Categorize GI infections by bacterial pathogenic mechanisms.

MSC: Remembering 26. If the acid-resistance genes of EHEC strains were deleted, the expected result would be that the strains would a. be better adapted to survive in the stomach. b. no longer be able to colonize the respiratory tract. c. have a higher oral infectious dose. d. have a lower oral infectious dose.

ANS: C DIF: Difficult REF: 22.5 OBJ: 22.5a Categorize GI infections by bacterial pathogenic mechanisms.

MSC: Analyzing

27. Karen is suffering from a gastrointestinal illness caused by a Gram-negative bacterium without flagella. Which of the following conditions could Karen have? a. salmonellosis c. hemolytic uremia syndrome b. shigellosis d. peptic ulcers ANS: B DIF: Moderate REF: 22.5 OBJ: 22.5a Categorize GI infections by bacterial pathogenic mechanisms.

MSC: Applying 28. The most common bacterial cause of diarrhea in the United States is a. E. coli. c. Campylobacter. b. Shigella. d. Salmonella.

ANS: D DIF: Easy REF: 22.5 OBJ: 22.5a Categorize GI infections by bacterial pathogenic mechanisms.

MSC: Understanding 29. Peritonitis and cholecystitis can result when ________ infects immunocompromised individuals. a. Campylobacter jejuni c. E. coli b. Salmonella enterica d. Shigella dysenteriae ANS: A DIF: Moderate REF: 22.5 OBJ: 22.5b Correlate bacterial virulence mechanisms to GI disease symptoms.

MSC: Understanding 30. Jim and his family were on vacation in sunny Florida. One evening after spending the day at the beach, Jim noticed a painful wound that he was not aware he had. After 24 hours without treatment, Jim was pronounced dead. What organism infected Jim? a. Listeria monocytogenes c. Vibrio cholerae b. Clostridium difficile d. Vibrio vulnificus ANS: D DIF: Moderate REF: 22.5 OBJ: 22.5b Correlate bacterial virulence mechanisms to GI disease symptoms.

MSC: Applying 31. What would be the expected result on the body if the pathogenicity island of Clostridium difficile were removed? a. an increase in production of TNF- b. a decrease in production of TNF- c. an increased ability to detect the toxin in a fecal sample d. an increased ability to identify the organism by PCR ANS: B DIF: Difficult REF: 22.5 OBJ: 22.5b Correlate bacterial virulence mechanisms to GI disease symptoms.

MSC: Analyzing 32. Within three hours of attending the church carnival, Maya and her family are all vomiting uncontrollably. What organism have they likely ingested? a. no organism—most likely a toxin from Staphylococcus aureus b. Listeria monocytogenes c. Salmonella typhimurium d. Campylobacter jejuni ANS: A DIF: Moderate REF: 22.5 OBJ: 22.5b Correlate bacterial virulence mechanisms to GI disease symptoms.

MSC: Applying 33. Yersinia enterocolitica infection should be treated with a. surgery. c. antibiotics. b. proton pump inhibitors. d. hydration.

ANS: D DIF: Easy REF: 22.5 OBJ: 22.5c Relate the treatment of GI infections to virulence of GI pathogens.

MSC: Understanding 34. Which of the following organisms might someday be prevented from causing infections by a vaccine? a. E. coli c. Salmonella b. Shigella d. Listeria ANS: B DIF: Moderate REF: 22.5 OBJ: 22.5d Evaluate treatment and prevention methods used for bacterial infections of the gastrointestinal tract.

MSC: Understanding 35. Infection with ________ could mimic symptoms of hepatitis. a. Entamoeba histolytica c. Cyclospora cayetanensis b. Cryptosporidium hominis d. Giardia intestinalis ANS: A DIF: Moderate REF: 22.6 OBJ: 22.6a Distinguish GI infections caused by protozoa from those caused by helminths.

MSC: Applying 36. Which of the following organisms is NOT transmitted by direct fecal-oral contact? a. Entamoeba c. Cyclospora b. Giardia d. Cryptosporidium ANS: C DIF: Moderate REF: 22.6 OBJ: 22.6a Distinguish GI infections caused by protozoa from those caused by helminths.

MSC: Understanding 37. Tapeworms are transmitted by the ________ route. a. fecal-environment-skin c. fecal-oral-environment-skin b. fecal-oral d. fecal-intermediate host-oral ANS: D DIF: Easy REF: 22.6 OBJ: 22.6b Describe the role of parasitic life cycles in the transmission and pathogenesis of parasitic GI diseases.

MSC: Understanding 38. If humans began engaging in regular cannibalism, which of the following might become more prevalent? a. Trichinella c. Necator b. Stongyloides d. Ascarsis ANS: A DIF: Moderate REF: 22.6 OBJ: 22.6b Describe the role of parasitic life cycles in the transmission and pathogenesis of parasitic GI diseases.

MSC: Applying 39. What type of organism is shown in the figure below?

a. tapeworm b. pinworm

c. whipworm d. hookworm

ANS: A DIF: Easy REF: 22.6 OBJ: 22.6c Generate a list of the diagnostic, prevention, and treatment options available for the parasitic diseases discussed.

MSC: Understanding 40. The problem with antihelminth drugs is that they are not able to a. completely eliminate the worm from the body. b. kill the worm. c. starve the worm. d. There is no problem with antihelminth drugs.

ANS: A DIF: Moderate REF: 22.6 OBJ: 22.6c Generate a list of the diagnostic, prevention, and treatment options available for the parasitic diseases discussed.

MSC: Understanding 41. CASE HISTORY A 2.1-kilogram (4.7-pound) female neonate was born at 32 weeks. A normal neonate averages 3.17 kg, or 7 pounds, and is born at 40 weeks. The baby was clearly in distress and was intubated at birth because of poor respiratory effort. A chest X-ray showed an infiltrate in the baby’s right lung. Her mother, Linda, presented at the time of delivery with lower abdominal pain, a temperature of 39 C (102 F), and a white cell count of 25,000/l (normal is 4,000–10,000). Blood cultures from Linda and her child grew Gram-positive coccobacilli. Mother and baby fully recovered after antibiotic treatment.

The physician later learned that Linda had recently visited Mexico, where she ate unpasteurized soft cheese called queso blanco.

Which bacterium, possessing virulence factors that enable it to cross the placental barrier, is the likely etiologic agent of Linda’s infection (and her baby’s)? a. Listeria monocytogenes c. Staphylococcus aureus b. Clostridium perfringens d. Corynebacterium diptheriae ANS: A DIF: Moderate REF: Case History 22.4 OBJ: 22.5a Categorize GI infections by bacterial pathogenic mechanisms.

MSC: Understanding COMPLETION 1. The gastrointestinal tract is a long tube extending from ________to________.

ANS: mouth; anus DIF: Easy

REF: 22.1

OBJ: 22.1a List the structural components of the digestive system and describe the relationship between them.

MSC: Remembering 2. The part of a tooth protruding outward from the gum is called the ________.

ANS: crown DIF: Easy REF: 22.1 OBJ: 22.1b Name the functions of different structures of the digestive system.

MSC: Remembering 3. During digestion, pepsin is secreted by ________.

ANS: chief cells DIF: Easy REF: 22.1 OBJ: 22.1c Explain the roles of specialized cells of the intestinal tract (chief cells, M cells, parietal cells, and mucous neck cells).

MSC: Understanding 4. Infections of the oral cavity start as ________.

ANS: biofilms DIF: Moderate REF: 22.2 OBJ: 22.2b Analyze how biofilms contribute to infections of the oral cavity.

MSC: Understanding 5. The most common sign of a gastrointestinal infection is ________, having three or more loose stools per day.

ANS: diarrhea DIF: Easy REF: 22.3 OBJ: 22.3a List the most common signs and symptoms associated with gastrointestinal infections.

MSC: Remembering 6. When intestinal mucosal cells increase ion secretion, ________ results.

ANS: secretory diarrhea DIF: Easy REF: 22.3 MSC: Remembering

OBJ: 22.3c Outline the general mechanisms of diarrhea.

7. Jack presents at the clinic with mild nausea, vomiting, abdominal pain, and jaundice. The most likely cause of Jack’s condition is ________.

ANS: hepatitis DIF: Moderate REF: 22.4 OBJ: 22.4a Match gastrointestinal symptoms to the viral infections that cause them.

MSC: Applying 8. Overcrowding/bad hygiene as well as eating undercooked seafood can result in ________.

ANS: hepatitis A DIF: Easy REF: 22.4 OBJ: 22.4c Discuss viral pathogenic mechanisms responsible for specific disease signs and symptoms in the gastrointestinal tract.

MSC: Understanding 9. CPE is an enterotoxin produced by ________.

ANS: Clostridium perfringens DIF: Easy REF: 22.5 OBJ: 22.5a Categorize GI infections by bacterial pathogenic mechanisms.

MSC: Remembering 10. People infected with ________ are treated with proton pump inhibitors and a high dose of antibiotics.

ANS: Helicobacter pylori DIF: Moderate REF: 22.5 OBJ: 22.5c Relate the treatment of GI infections to virulence of GI pathogens.

MSC: Understanding 11. Giardiasis is caused by the ________ Giardia intestinalis.

ANS: protozoa DIF: Easy REF: 22.6 OBJ: 22.6a Distinguish GI infections caused by protozoa from those caused by helminths.

MSC: Remembering 12. A liver biopsy is used to diagnose infection caused by the ________ helminth.

ANS: liver fluke DIF: Easy REF: 22.6 OBJ: 22.6c Generate a list of the diagnostic, prevention, and treatment options available for the parasitic diseases discussed.

MSC: Remembering SHORT ANSWER 1. Lactobacillus species are a major type of probiotic. Describe one positive aspect of Lactobacillus and one negative aspect.

ANS: A variety of answers are possible. The positive aspect could center on the species’ use as a probiotic or as part of the natural flora in the gut or vaginal canal that prevents pathogens from growing. The negative aspect could center on its cavity-causing role in the oral microbiota.

DIF: Moderate REF: 22.2 OBJ: 22.2a List microbes comprising normal microbiota of the oral cavity.

MSC: Analyzing 2. How would you distinguish between gingivitis, periodontal disease, and trench mouth?

ANS: Gingivitis is the most mild and is inflammation of the gums. Periodontal disease is when the inflammation of the gums has spread far enough so that the gum line is receding from the teeth and the tender gums bleed very easily. Trench mouth contains necrosis that shows as a gray film. There are also crater-like canker sores between teeth and gums as well as bad breath and a bad taste in the mouth.

DIF: Moderate REF: 22.2 OBJ: 22.2c Compare the signs and symptoms of common infections of the oral cavity.

MSC: Applying 3. Explain why a gastrointestinal pathogen would want to cause diarrhea when it could easily result in its removal from the host.

ANS: Pathogens that cause diarrhea may want to leave the host to escape to a new host before the current host is killed or to escape to a new host before the excessively triggered immune system of the current host kills the bacterium.

DIF: Moderate REF: 22.3 OBJ: 22.3b Correlate microbial pathogenic mechanisms with the presenting signs and symptoms of gastrointestinal infections.

MSC: Analyzing 4. What is the likely cause of the condition suffered by the individual who said the sentence below?

Explain the mistake.

“I went on a cruise last week and was so sick with the stomach flu!”

ANS: The individual suffered from norovirus. The mistake is that norovirus does not cause the flu, though some of the fever and myalgia symptoms are the same. Norovirus is a gastrointestinal virus, while the flu is caused by influenza, a respiratory virus.

DIF: Difficult REF: 22.4 OBJ: 22.4b List routes of transmission of specific viral diseases of the gastrointestinal tract.

MSC: Analyzing 5. Explain how infections with Yersinia enterocolitica can cause symptoms outside of the gastrointestinal tract.

ANS: Yersinia infections can spread from the jejunum and ileum into the mesenteric lymph nodes, resulting in inflammation of the lymph nodes that causes pain often mistaken for appendicitis. It can also enter the blood stream and spread to other organs, causing focal infections.

DIF: Moderate REF: 22.5 OBJ: 22.5b Correlate bacterial virulence mechanisms to GI disease symptoms.

MSC: Applying

6. A recall on spinach potentially contaminated with Yersinia enterocolitica occurs. Kurt hears about the recall but has kept his spinach in the refrigerator. He figures that even if his spinach had been contaminated, the organism will not grow in the refrigerator. Therefore, the number of organisms present will be so small that even if his spinach is contaminated, he will not be affected. Is Kurt correct? Explain.

ANS: Kurt is incorrect. Y. enterocolitica has the ability to grow at refrigeration temperatures, so if his spinach is contaminated, it will only become more contaminated by sitting in the refrigerator.

DIF: Moderate REF: 22.5 OBJ: 22.5d Evaluate treatment and prevention methods used for bacterial infections of the gastrointestinal tract.

MSC: Analyzing 7. Describe the life cycle of the tapeworm.

ANS: The tapeworm matures in the human intestine and releases its eggs into human feces. Grazing animals known as intermediate hosts ingest the eggs. The acid of the intermediate host’s stomach releases the larvae. The larvae travel to the GI system, the circulatory system, and finally the muscle, where they become cysts. Humans eating undercooked meat of infected animals will then become infected.

DIF: Moderate REF: 22.6 OBJ: 22.6b Describe the role of parasitic life cycles in the transmission and pathogenesis of parasitic GI diseases.

MSC: Applying 8. CASE HISTORY Tammy, a six-year-old girl from Montgomery County, Pennsylvania, arrived at a hospital’s emergency department with bloody diarrhea, a temperature of 39 C (102.2 F), abdominal cramping, and vomiting. She was admitted to the hospital five days after a kindergarten field trip to the local dairy farm. The child’s health history was otherwise unremarkable. At the time of hospital admission, her parents were asked about Tammy’s activities during the trip. They confirmed that Tammy bought a snack while at the farm. The laboratory reported that her fecal smear was positive for leukocytes and contained Gram-negative rods that produced Shiga toxins 1 and 2. Subsequent testing of the isolate’s serotype revealed E. coli O157:H7. By this time, Tammy had developed additional problems. Her face and hands had become puffy, she had decreased urine output despite being given IV fluids (suggesting kidney damage), and she was beginning to develop some neurological abnormalities. Laboratory analyses of blood samples revealed thrombocytopenia (reduced blood platelet count) and confirmed hemolytic uremic syndrome (HUS, renal failure). The child was given intravenous fluid and electrolyte replacement. Antibiotics were not administered, and Tammy eventually recovered.

Why did physicians choose not to treat Tammy with antibiotics, despite her disease’s bacterial etiology?

ANS: Shiga toxin is the virulence factor responsible for the severe nature of Tammy’s disease. Antibiotic therapy can increase the amount of toxin released into the body, potentially shortening the duration of infection but increasing the severity of the disease.

DIF: Moderate REF: Case History 22.3 OBJ: 22.5c Relate the treatment of GI infections to virulence of GI pathogens.

MSC: Understanding 9. CASE HISTORY

Tammy, a six-year-old girl from Montgomery County, Pennsylvania, arrived at a hospital’s emergency department with bloody diarrhea, a temperature of 39 C (102.2 F), abdominal cramping, and vomiting. She was admitted to the hospital five days after a kindergarten field trip to the local dairy farm. The child’s health history was otherwise unremarkable. At the time of hospital admission, her parents were asked about Tammy’s activities during the trip. They confirmed that Tammy bought a snack while at the farm. The laboratory reported that her fecal smear was positive for leukocytes and contained Gram-negative rods that produced Shiga toxins 1 and 2. Subsequent testing of the isolate’s serotype revealed E. coli O157:H7. By this time, Tammy had developed additional problems. Her face and hands had become puffy, she had decreased urine output despite being given IV fluids (suggesting kidney damage), and she was beginning to develop some neurological abnormalities. Laboratory analyses of blood samples revealed thrombocytopenia (reduced blood platelet count) and confirmed hemolytic uremic syndrome (HUS, renal failure). The child was given intravenous fluid and electrolyte replacement. Antibiotics were not administered, and Tammy eventually recovered.

E. coli O157:H7 is Verotoxin-producing Escherichia coli, or EHEC. How do these differ from Enterotoxigenic Escherichia coli, or ETEC, and how would Tammy’s disease progress have been observably different if she had been infected with ETEC instead?

ANS: EHEC and ETEC differ primarily in toxin production, Shiga versus LT, and thus the form of diarrhea is generally different (bloody versus watery). ETEC does not progress to HUS, which is also toxin dependent.

DIF: Difficult REF: Case History 22.3 OBJ: 22.5b Correlate bacterial virulence mechanisms to GI disease symptoms.

MSC: Analyzing

Chapter 23: Infections of the Urinary and Reproductive Tracts LEARNING OBJECTIVES 23.1a List the function of each structural component of the male and female urinary tracts.

23.1b Explain the relationship between the upper and lower urinary tract anatomy and physiology.

23.1c Discuss the significance of structural differences between the male and female urinary tract as they relate to infections.

23.2a Discuss the role of physical and hormonal factors in the development of urinary tract infections in women.

23.2b Explain the relationships between lower and upper urinary tract infections.

23.2c Compare and contrast the signs and symptoms of common urinary tract infections.

23.2d List treatments for the most common etiologies of urinary tract infections.

23.3a List the structural components of the male and female reproductive tracts.

23.3b Explain the function of each component of the male and female reproductive tracts.

23.3c Discuss the significance of structural differences between the male and female reproductive tracts as they relate to infections.

23.4a Relate the signs and symptoms of sexually transmitted infections to their microbial etiology.

23.4b Separate complications of each sexually transmitted infection according to the disease progression.

23.4c Explain the impact of gender on the development of sexually transmitted infections and their complications.

23.4d List prevention and treatment options available for sexually transmitted infections.

23.5a Relate signs and symptoms of non-sexually transmitted infections to their microbial etiology.

23.5b Explain the role of the vaginal microbiome in prevention and/or development of non-sexually transmitted infections of the reproductive tract.

23.5c List treatment options available for non-sexually transmitted infections of the reproductive tract.

MULTIPLE CHOICE 1. The urinary tract is composed of all of the following EXCEPT the a. vagina. c. bladder. b. kidneys. d. urethra.

ANS: A DIF: Easy REF: 23.1 OBJ: 23.1a List the function of each structural component of the male and female urinary tracts.

MSC: Remembering 2. All of the following are true about the glomerulus EXCEPT that a. it is surrounded by the Bowman’s capsule. b. it is made up of small capillaries. c. during filtration large molecules and blood enter into the Bowman’s capsule. d. it is damaged in acute post-streptococcal glomerulonephritis.

ANS: C DIF: Moderate REF: 23.1 OBJ: 23.1a List the function of each structural component of the male and female urinary tracts.

MSC: Understanding 3. Which of the following is true about the urinary system? a. The wall of the ureters is made of skeletal muscle that is voluntary.

b. Filtrate is collected in the bladder. c. The urinary bladder is made up of squamous epithelial cells. d. Excess water is removed and returned to the vascular system in the collecting duct.

ANS: D DIF: Moderate REF: 23.1 OBJ: 23.1b Explain the relationship between the upper and lower urinary tract anatomy and physiology.

MSC: Understanding 4. The figure below illustrates a Chlamydia infection process. To what structure is arrow B pointing?

a. elementary bodies b. reticulate body

c. the nucleus d. inclusions

ANS: B DIF: Easy REF: 23.4 OBJ: 23.4b Separate complications of each sexually transmitted infection according to the disease progression.

MSC: Applying 5. The cell shown below is infected with Chlamydia. Which are considered replicating bodies?

a. elementary bodies b. reticulate bodies

c. the nucleus d. inclusions

ANS: A DIF: Moderate REF: 23.4 OBJ: 23.4b Separate complications of each sexually transmitted infection according to the disease progression.

MSC: Applying 6. Which of the following is caused by an opportunistic pathogen? a. genital herpes c. candidiasis b. gonorrhea d. chancroid ANS: C DIF: Easy REF: 23.4 OBJ: 23.4a Relate the signs and symptoms of sexually transmitted infections to their microbial etiology.

MSC: Understanding 7. All of the following explain why women get urinary tract infections more often than men EXCEPT a. the location of the urethra in women is closer to the anus than in men. b. sexual activity. c. bladder incontinence in postmenopausal women. d. the urethra in women is longer than in men.

ANS: D DIF: Easy REF: 23.2 OBJ: 23.2a Discuss the role of physical and hormonal factors in the development of urinary tract infections in women.

MSC: Understanding 8. Reoccurring UTIs can be a result of all of the following EXCEPT a. birth control pills. b. biofilm formation. c. improper clearance after antibiotic treatment. d. reintroduction of the organism.

ANS: A DIF: Moderate REF: 23.2 OBJ: 23.2c Compare and contrast the signs and symptoms of common urinary tract infections.

MSC: Analyzing 9. All of the following cause UTIs EXCEPT a. E. coli. b. S. aureus.

c. S. pyogenes. d. C. trichomatis.

ANS: C DIF: Easy REF: 23.2 OBJ: 23.2c Compare and contrast the signs and symptoms of common urinary tract infections.

MSC: Remembering 10. Which of the following is the most difficult to treat with chemotherapeutic agents? a. gonorrhea c. syphilis b. genital herpes d. trichomoniasis ANS: B DIF: Moderate REF: 23.4 OBJ: 23.4d List prevention and treatment options available for sexually transmitted infections.

MSC: Understanding 11. Recurring vesicles on the surface of human skin are symptoms of a. candidiasis. c. genital herpes. b. trichomoniasis. d. lymphogranuloma venereum.

ANS: C DIF: Easy REF: 23.4 OBJ: 23.4a Relate the signs and symptoms of sexually transmitted infections to their microbial etiology.

MSC: Remembering

12. Someone is said to have a primary HSV infection when the a. patient does not have detectable antibodies but a positive PCR test. b. infection settles into the nerve root. c. latent virus is reactivated. d. virus is activated by stress or UV exposure.

ANS: A DIF: Moderate REF: 23.4 OBJ: 23.4a Relate the signs and symptoms of sexually transmitted infections to their microbial etiology.

MSC: Analyzing 13. The observation of a “strawberry” cervix is a symptom of a. lymphogranuloma venereum. c. genital herpes. b. candidiasis. d. trichomoniasis.

ANS: D DIF: Easy REF: 23.4 OBJ: 23.4c Explain the impact of gender on the development of sexually transmitted infections and their complications.

MSC: Understanding 14. All of the following are true about a chlamydial infection EXCEPT that a. it is caused by a Gram-negative intracellular pathogen. b. it is not very common in the United States. c. women are usually asymptomatic. d. the organism is able to “hitchhike” on sperm.

ANS: B DIF: Moderate REF: 23.4 OBJ: 23.4c Explain the impact of gender on the development of sexually transmitted infections and their complications.

MSC: Understanding 15. Which of the following is part of the internal male reproductive system? a. penis c. testes b. scrotum d. vas deferens ANS: D DIF: Easy REF: 23.3 OBJ: 23.3a List the structural components of the male and female reproductive tracts.

MSC: Remembering 16. Which of the following is considered to be part of the upper urinary system? a. urinary bladder c. ureters b. vagina d. urethra ANS: C DIF: Easy REF: 23.1 OBJ: 23.1b Explain the relationship between the upper and lower urinary tract anatomy and physiology.

MSC: Remembering 17. All of the following are ways that an infection can be established in the urinary tract EXCEPT an infection a. acquired in the kidney. c. from the urethra. b. in the vaginal canal. d. from the bladder.

ANS: B DIF: Difficult REF: 23.2 OBJ: 23.2a Discuss the role of physical and hormonal factors in the development of urinary tract infections in women.

MSC: Analyzing 18. Which of these is NOT an antimicrobial feature of the urinary system? a. physiological valves found in the ureter

b. pH of the urine c. flushing action of urine d. the use of the urethra for seminal fluid in women ANS: D DIF: Moderate REF: 23.2 OBJ: 23.2d List treatments for the most common etiologies of urinary tract infections.

MSC: Analyzing 19. Which of the following is true about the female reproductive system? a. The entire female reproductive system is internal. b. The mature oocyte is deposited directly into the uterus. c. The uterus ends at the opening of the vagina. d. The uterus is the site of fertilization.

ANS: A DIF: Moderate REF: 23.3 OBJ: 23.3b Explain the function of each component of the male and female reproductive tracts.

MSC: Understanding 20. All of the following are risk behaviors that lead to the acquisition of an STI EXCEPT a. abstinence. c. multiple sex partners. b. unprotected sex. d. drug abuse.

ANS: A DIF: Easy REF: 23.3 OBJ: 23.3c Discuss the significance of structural differences between the male and female reproductive tracts as they relate to infections.

MSC: Remembering 21. Which of the following is an example of a non-sexually transmitted infection? a. syphilis c. gonorrhea b. yeast infection d. pyelonephritis ANS: B DIF: Moderate REF: 23.5 OBJ: 23.5a Relate signs and symptoms of non-sexually transmitted infections to their microbial etiology.

MSC: Understanding 22. What is the treatment for bacterial vaginosis? a. oral and topical antibiotics b. antifungals

c. antivirals d. There is no treatment.

ANS: A DIF: Moderate REF: 23.5 OBJ: 23.5c List treatment options available for non-sexually transmitted infections of the reproductive tract.

MSC: Remembering 23. Vaginal itching and cheesy discharge are symptoms of a. bacterial vaginosis. c. candidiasis. b. genital herpes. d. trichomoniasis.

ANS: C DIF: Easy REF: 23.5 OBJ: 23.5a Relate signs and symptoms of non-sexually transmitted infections to their microbial etiology.

MSC: Remembering 24. All of the following can cause non-sexually transmitted infections of the reproductive tract EXCEPT a. sexual intercourse. c. a change in vaginal microbiome. b. fluctuations in pH. d. IV drug abuse.

ANS: D DIF: Moderate REF: 23.5 OBJ: 23.5b Explain the role of the vaginal microbiome in prevention and/or development of non-

sexually transmitted infections of the reproductive tract.

MSC: Analyzing

25. Which of the following is caused by Chlamydia? a. bacterial vaginosis c. candidiasis b. genital herpes d. lymphogranuloma venereum ANS: D DIF: Easy REF: 23.4 OBJ: 23.4c Explain the impact of gender on the development of sexually transmitted infections and their complications. MSC: Remembering 26. Which of the following diseases causes a skin rash, hair loss, malaise, and fever? a. gonorrhea c. NGU b. syphilis d. genital herpes ANS: B DIF: Moderate REF: 23.4 OBJ: 23.4a Relate the signs and symptoms of sexually transmitted infections to their microbial etiology.

MSC: Understanding 27. Genital warts are NOT a. transmitted by direct contact. b. caused by papillomaviruses.

c. always precancerous. d. treated by removing them.

ANS: C DIF: Difficult REF: 23.4 OBJ: 23.4b Separate complications of each sexually transmitted infection according to the disease progression.

MSC: Analyzing 28. The normal microbiota of the adult vagina consist primarily of a. Lactobacillus. c. Mycobacterium. b. Streptococcus. d. Candida.

ANS: A DIF: Easy REF: 23.5 OBJ: 23.5b Explain the role of the vaginal microbiome in prevention and/or development of nonsexually transmitted infections of the reproductive tract.

MSC: Remembering 29. Which of the following recurs at the initial site of infection? a. gonorrhea c. genital herpes b. syphilis d. chancroid ANS: C DIF: Moderate REF: 23.4 OBJ: 23.4b Separate complications of each sexually transmitted infection according to the disease progression.

MSC: Understanding 30. Pelvic inflammatory disease CANNOT a. cause sterility and chronic pain. b. be caused by N. gonorrhoeae.

c. be transmitted sexually. d. be caused by T. pallidum.

ANS: D DIF: Moderate REF: 23.5 OBJ: 23.5a Relate signs and symptoms of non-sexually transmitted infections to their microbial etiology.

MSC: Understanding 31. A patient presents with fever and extensive lesions of the labia minora. Her VDRL test was negative.

What is the most likely treatment? a. metronidazole c. cephalosporins b. acyclovir d. No treatment is available.

ANS: B

DIF: Difficult

REF: 23.4

OBJ: 23.4d List prevention and treatment options available for sexually transmitted infections.

MSC: Analyzing 32. Which of the following is NOT a portal of entry for STIs in women? a. anus c. urethra b. vagina d. ureter ANS: D DIF: Moderate REF: 23.3 OBJ: 23.3a List the structural components of the male and female reproductive tracts.

MSC: Applying 33. Trichomoniasis is caused by a a. protozoan. b. bacteria.

c. virus. d. eukaryote.

ANS: A DIF: Difficult REF: 23.4 OBJ: 23.4a Relate the signs and symptoms of sexually transmitted infections to their microbial etiology.

MSC: Understanding 34. The human bladder can accommodate 400–600 milliliters of urine because it is a. triangular shaped. b. composed of transitional epithelium. c. made of muscular tissue. d. The bladder can only hold 5–10 milliliters of urine.

ANS: B DIF: Moderate REF: 23.1 OBJ: 23.1b Explain the relationship between the upper and lower urinary tract anatomy and physiology.

MSC: Applying 35. Why are UTIs considered serious and why should they be treated promptly? a. They are uncomfortable and are treated to control pain. b. If left untreated, the infection can travel up into the kidneys, causing a more serious infection. c. They are caused by notifiable pathogens and should be reported to the health department. d. They should be treated promptly to prevent them from becoming recurring infections.

ANS: B DIF: Moderate REF: 23.2 OBJ: 23.2b Explain the relationships between lower and upper urinary tract infections.

MSC: Applying 36. All of the following are ways that HIV can be transmitted from person to person EXCEPT a. mother to fetus. c. kissing. b. sexual contact. d. blood transfusion.

ANS: C DIF: Easy REF: 23.4 OBJ: 23.4b Separate complications of each sexually transmitted infection according to the disease progression.

MSC: Understanding 37. Which of the following is NOT considered a clinical progression of an HIV infection? a. increase in immune function c. latency b. seroconversion d. AIDS ANS: A DIF: Easy REF: 23.4 OBJ: 23.4a Relate the signs and symptoms of sexually transmitted infections to their microbial etiology.

MSC: Understanding

38. The purpose of the fimbriae on the end of the fallopian tube is to a. help the fallopian tube move into position. b. perform a sweeping motion to capture the ovum. c. keep microbes out of the fallopian tube. d. help to fertilize the ovum.

ANS: B DIF: Easy REF: 23.3 OBJ: 23.3b Explain the function of each component of the male and female reproductive tracts.

MSC: Remembering 39. Yeast infections are more difficult for clinicians to treat than bacterial infections because a. yeast infections are caused by intracellular pathogens. b. yeast cells are multidrug resistant. c. yeast is multicellular and thus is harder to kill. d. yeast infections are caused by Candida species, which are eukaryotic in nature.

ANS: D DIF: Difficult REF: 23.5 OBJ: 23.5c List treatment options available for non-sexually transmitted infections of the reproductive tract.

MSC: Analyzing 40. What is the treatment for severe pyelonephritis? a. antivirals c. oral antibiotics b. IV antibiotics d. There is no treatment.

ANS: B DIF: Moderate REF: 23.2 OBJ: 23.2d List treatments for the most common etiologies of urinary tract infections.

MSC: Remembering 41. CASE HISTORY Lashandra is 24 years old and had been experiencing increased frequency of urination and dysuria (pain or burning with urination) over the previous three days. This was the first time Lashandra had ever suffered from persisting dysuria. She consulted her general practitioner, who requested a midstream specimen of urine. Upon microscopic examination, the urine was found to contain more than 50 leukocytes/l (normal is fewer than 5) and 35 red blood cells/ml (normal is 3–20). Epithelial cells from the urogenital area contaminate a midstream specimen if the specimen is not collected properly. No squamous epithelial cells (skin cells) were seen, indicating a well-collected midstream catch. The urine culture plated on agar medium yielded more than 105 colonies/ml (meaning more than 105 organisms/ml in the urine) of a facultative, anaerobic, Gram-negative bacillus that can ferment lactose.

Lashandra’s infection is likely NOT a. initiated by self-inoculation with E. coli. b. cystitis treatable by oral antibiotic. c. characterized by bacteriuria and urethritis. d. descending pyelonephritis.

ANS: D DIF: Moderate REF: Case History 23.1 OBJ: 23.2c Compare and contrast the signs and symptoms of common urinary tract infections.

MSC: Analyzing 42. CASE HISTORY

Lashandra is 24 years old and had been experiencing increased frequency of urination and dysuria (pain or burning with urination) over the previous three days. This was the first time Lashandra had ever suffered from persisting dysuria. She consulted her general practitioner, who requested a midstream specimen of urine. Upon microscopic examination, the urine was found to contain more than 50 leukocytes/ml (normal is fewer than 5) and 35 red blood cells/l (normal is 3–20). Epithelial cells from the urogenital area contaminate a midstream specimen if the specimen is not collected properly. No squamous epithelial cells (skin cells) were seen, indicating a well-collected midstream catch. The urine culture plated on agar medium yielded more than 105 colonies/ml (meaning more than 105 organisms/ml in the urine) of a facultative, anaerobic, Gram-negative bacillus that can ferment lactose.

The purpose of collecting a midstream specimen of urine is to a. ensure a sterile specimen is collected. b. minimize the number of contaminating organisms. c. minimize the amount of urine that is collected. d. maximize the number of organisms collected.

ANS: B DIF: Easy REF: Case History 23.1 OBJ: 23.2c Compare and contrast the signs and symptoms of common urinary tract infections.

MSC: Understanding COMPLETION 1. There are two types of urinary tract infections: bladder infections, or ________, and kidney infections, or ________.

ANS: cystitis; pyelonephritis DIF: Easy REF: 23.2 OBJ: 23.2c Compare and contrast the signs and symptoms of common urinary tract infections.

MSC: Remembering 2. Primary syphilis is an inflammatory reaction at the site of infection called a ________.

ANS: chancre DIF: Easy REF: 23.4 OBJ: 23.4a Relate the signs and symptoms of sexually transmitted infections to their microbial etiology.

MSC: Understanding 3. Sperm are produced in the testes and mature inside the male in a process known as ________.

ANS: spermatozoa DIF: Easy REF: 23.3 OBJ: 23.3b Explain the function of each component of the male and female reproductive tracts.

MSC: Understanding 4. The vaginal pH is maintained by the species Lactobacillus, which produces ________.

ANS: lactic acid DIF: Moderate REF: 23.5 OBJ: 23.5b Explain the role of the vaginal microbiome in prevention and/or development of non-

sexually transmitted infections of the reproductive tract.

MSC: Remembering

5. Highly active antiretroviral therapy, or HAART, is used to treat ________.

ANS: HIV DIF: Easy REF: 23.4 OBJ: 23.4d List prevention and treatment options available for sexually transmitted infections.

MSC: Understanding SHORT ANSWER 1. Nearly 70% of patients seen in STI clinics are men. Offer a reason why men are more likely to seek treatment than women. Why is it important that women seek treatment for STIs? ANS: Men are more likely to seek treatment than women because their genitalia is external and they can see when an infection is occurring (i.e., formed lesions, warts, etc.). It is important that women seek treatment for STIs because infections like this can be “silent” in women. Prolonged STI infections can lead to the development of other complications for women, such as pelvic inflammatory disease or even infertility.

DIF: Difficult REF: 23.3 OBJ: 23.3a List the structural components of the male and female reproductive tracts.

MSC: Evaluating 2. What conclusion can you make about your patient regarding the urinalysis data below?

ANS: This patient has dark urine, which would suggest concentration of the urine. The urine is also positive for leukocytes, which are white blood cells, nitrite, and blood. This would all suggest that the patient has a UTI and should be treated with antibiotics to prevent further urinary tract complications.

DIF: Difficult REF: 23.2 OBJ: 23.2c Compare and contrast the signs and symptoms of common urinary tract infections.

MSC: Applying 3. This figure below shows a nephron. Please label the following on the figure and explain the steps involved in the production of urine.

• Glomerulus • Bowman’s capsule • Collecting duct • Blood capillaries ANS: Small molecules move from the blood into the Bowman’s capsule, leaving large molecules and blood cells behind. Among the small molecules that pass through is urea, a toxic waste product of protein metabolism. The fluid in the capsule is called filtrate and proceeds through the rest of the nephron.

When the filtrate reaches the collecting duct, the extra water is removed and returned back to the blood. What remains in the collecting duct is urine that will flow into the ureter.

DIF: Difficult REF: 23.1 OBJ: 23.1a List the function of each structural component of the male and female urinary tracts.

MSC: Applying 4. What parts of the figure below are affected by pelvic inflammatory disease? Discuss the long-term consequences of pelvic inflammatory disease.

ANS: Students should circle the uterus and fallopian tubes.

The damage produced by PID can lead to tubal pregnancies, infertility, and chronic pelvic pain.

PID is often subclinical, but symptomatic patients can present with severe low abdominal pain, fever, nausea, and vomiting.

DIF: Difficult

REF: 23.3

OBJ: 23.3c Discuss the significance of structural differences between the male and female reproductive tracts as they relate to infections.

MSC: Applying 5. The recombinant HPV vaccine Gardasil offers protection against various serotypes of HPV; it is also known as an anticancer vaccine. Speculate as to why it is referred to as an anticancer vaccine.

ANS: Gardasil is a vaccine that targets the serotypes 6, 11, 16, and 18. These HPV serotypes are associated with the development of cervical cancer in infected women. By receiving the vaccination, one decreases the odds of contracting the HPV virus, especially the serotypes that are associated with cancer.

DIF: Difficult REF: 23.4 OBJ: 23.4d List prevention and treatment options available for sexually transmitted infections.

MSC: Analyzing 6. CASE HISTORY Lashandra is 24 years old and had been experiencing increased frequency of urination and dysuria (pain or burning with urination) over the previous three days. This was the first time Lashandra had ever suffered from persisting dysuria. She consulted her general practitioner, who requested a midstream specimen of urine. Upon microscopic examination, the urine was found to contain more than 50 leukocytes/l (normal is fewer than 5) and 35 red blood cells/l (normal is 3–20). Epithelial cells from the urogenital area contaminate a midstream specimen if the specimen is not collected properly.

No squamous epithelial cells (skin cells) were seen, indicating a well-collected midstream catch. The urine culture plated on agar medium yielded more than 105 colonies/ml (meaning more than 105 organisms/ml in the urine) of a facultative, anaerobic, Gram-negative bacillus that can ferment lactose.

Lashandra’s physician is not likely to be surprised by the diagnosis of a UTI in a woman her age.

Discuss Lashandra’s potential risk factors for this disease.

ANS: Women are at increased risk of UTIs for many reasons. Students may suggest possibilities not directly discussed in the case history, such as sexual activity, or refer to risk factors that are clearly present, such as the anatomical differences in the urinary tracts of males and females.

DIF: Moderate REF: Case History 23.1 OBJ: 23.2a Discuss the role of physical and hormonal factors in the development of urinary tract infections in women.

MSC: Understanding 7. CASE HISTORY Odonna, a pregnant 18-year-old woman, came to the Nassau County, New York, urgent-care clinic with a low-grade fever, malaise, and headache. She was sent home with a diagnosis of influenza. She again sought treatment seven days later after she discovered a macular rash (flat, red) developing on her trunk, arms, palms of her hands, and soles of her feet. She thought maybe she was allergic to the new soap she was using, but the rash was not itchy or painful. Further questioning of the patient revealed that one year ago she had a painless ulcer on her vagina that healed spontaneously. She was diagnosed with secondary syphilis, a stage of the disease that can mimic many other conditions. She was given a single intramuscular injection of penicillin and told that her sexual partners had to be treated as well.

If Odonna’s infection had not been correctly diagnosed at this stage, how might the disease have progressed, and what complications would she be likely to face? Would these be different if the patient were male?

ANS: Untreated secondary syphilis can lead to tertiary syphilis, progressing potentially to neurosyphilis and death. Congenital syphilis is specifically a risk for the offspring of female patients. The progression of secondary syphilis to tertiary syphilis is not different between male and female patients.

DIF: Moderate REF: Case History 23.3 OBJ: 23.4c Explain the impact of gender on the development of sexually transmitted infections and their complications.

MSC: Analyzing

Chapter 24: Infections of the Central Nervous System LEARNING OBJECTIVES 24.1a Describe the functional organization of the central nervous system.

24.1b Explain how meninges and cerebrospinal fluid protect the central nervous system.

24.1c Describe the differences between two major types of neurons.

24.1d Correlate the anatomy of the central nervous system to the symptoms of CNS infections.

24.2a Categorize central nervous system infections by the anatomical structures affected.

24.2b Use key laboratory information to distinguish types of CNS infections.

24.2c Compare and contrast the roles of meninges and cerebrospinal fluid in the pathogenesis of CNS infections.

24.3a Classify viral CNS infections by their mode of transmission.

24.3b Explain the role of reservoirs in pathogenesis and prevention of viral diseases of the central nervous system.

24.3c Outline clinical diagnoses of viral CNS infections according to the patient’s history, signs, and symptoms.

24.3d Recommend treatment and prevention options for different viral CNS infections.

24.4a Identify risk factors for each of the bacterial CNS diseases.

24.4b Describe how different bacteria overcome host defenses to cause CNS disease.

24.4c List patient history information and clinical signs and symptoms specific to each bacterial pathogen of the central nervous system.

24.4d Relate pathogenesis of bacterial CNS diseases to prevention and treatment modalities used.

24.5a Name fungi that cause CNS disease.

24.5b Describe the role of host immunity in fungal infections of the CNS. 24.5c Define fungal CNS infections in the context of environmental exposure risks.

24.5d Identify diagnostic methods and treatment options for different fungal CNS infections.

24.6a Compare and contrast parasites and prions.

24.6b Evaluate acquisition of parasitic CNS infections.

24.6c Explain the role of host immune responses in parasitic and prion CNS disease.

24.6d Name prevention and treatment options for parasitic and prion CNS disease.

MULTIPLE CHOICE 1. The part of the nervous system that collects data from the environment is the a. meninges. c. cerebrospinal fluid. b. central nervous system. d. peripheral nervous system.

ANS: D DIF: Easy REF: 24.1 OBJ: 24.1a Describe the functional organization of the central nervous system.

MSC: Remembering 2. What is the correct order of the meninges, beginning from the most outer structures? a. pia mater, dura mater, arachnoid c. dura mater, arachnoid, pia mater b. pia mater, arachnoid, dura mater d. dura mater, pia mater, arachnoid ANS: C DIF: Moderate REF: 24.1 OBJ: 24.1b Explain how meninges and cerebrospinal fluid protect the central nervous system.

MSC: Understanding 3. Motor neurons send information a. from the CNS to the periphery. b. from the periphery to the CNS.

c. in both directions. d. from receptors.

ANS: A DIF: Easy REF: 24.1 OBJ: 24.1c Describe the differences between two major types of neurons.

MSC: Remembering 4. Which of the following is true about myelin sheaths? a. They slow down nerve impulses. b. They are made up of a protein molecule called myelin. c. They are destroyed in certain disorders such as multiple sclerosis. d. They cover all neuronal axons.

ANS: C DIF: Moderate REF: 24.1 OBJ: 24.1d Correlate the anatomy of the central nervous system to the symptoms of CNS infections.

MSC: Understanding 5. Microorganisms travel to the CNS by all of the following methods EXCEPT a. migration from distal sites. b. as toxins traveling along peripheral nerves. c. through infecting bone. d. through the lymphatic system.

ANS: D DIF: Moderate REF: 24.2 OBJ: 24.2a Categorize central nervous system infections by the anatomical structures affected.

MSC: Understanding 6. The symptoms of tetanus are due to a. tetanospasmin. b. endospore formation.

c. inflammation. d. the relaxation of muscles.

ANS: A DIF: Easy REF: 24.4 OBJ: 24.4c List patient history information and clinical signs and symptoms specific to each bacterial pathogen of the central nervous system.

MSC: Remembering 7. All of the following are caused by prions EXCEPT a. sheep scrapie. c. rabies. b. kuru. d. bovine spongiform encephalopathy.

ANS: C DIF: Moderate REF: 24.6 OBJ: 24.6a Compare and contrast parasites and prions.

MSC: Analyzing

8. Naegleria fowleri is commonly acquired through a. mosquito bites. b. ingestion of water contaminated with fecal material. c. exposure to bird droppings. d. swimming in warm ponds or streams.

ANS: D DIF: Easy REF: 24.6 OBJ: 24.6b Evaluate acquisition of parasitic CNS infections.

MSC: Remembering

9. The initial treatment for tetanus in an unimmunized person with a puncture wound is a. supportive care. c. penicillin.

b. tetanus toxoid.

d. debridement.

ANS: B DIF: Moderate REF: 24.4 OBJ: 24.4d Relate pathogenesis of bacterial CNS diseases to prevention and treatment modalities used.

MSC: Analyzing 10. The image below shows a CT scan of a brain displaying disease. The arrow points to

a. a brain abscess. b. encephalitis.

c. myelitis. d. a normal brain.

ANS: B DIF: Difficult REF: 24.2 OBJ: 24.2b Use key laboratory information to distinguish types of CNS infections.

MSC: Analyzing 11. Which of the following vaccine characteristics is/are mismatched with its/their respective vaccine type?

Salk Vaccine Sabin Vaccine 1. Consists of a formalin-inactivated virus 4. Consists of a live, attenuated virus 2. Administered orally 5. Administered orally 3. Requires booster doses 6. Provides community immunity a. 1, 3, and 5 b. 4, 5, and 6

c. 1 and 3 only d. 2 only

ANS: D DIF: Difficult REF: 24.3 OBJ: 24.3b Explain the role of reservoirs in pathogenesis and prevention of viral diseases of the central nervous system.

MSC: Analyzing 12. Which of the following pairs is mismatched? a. tetanus—releases potent neurotoxin b. botulism—stimulates transmission of nerve impulse c. poliomyelitis—multiplication of virus occurs in throat and small intestine d. rabies—destroys cells of the CNS ANS: B DIF: Moderate REF: 24.4 OBJ: 24.4a Identify risk factors for each of the bacterial CNS diseases.

MSC: Analyzing 13. Which of the following is true about CSF? a. Inflammatory cells are found in both healthy and unhealthy CSF. b. It helps to diagnose infections of the central nervous system. c. The identification of PMNs in CSF indicates a viral infection.

d. CSF is collected via the placement of a shunt in the vertebral column.

ANS: B DIF: Difficult REF: 24.2 OBJ: 24.2c Compare and contrast the roles of meninges and cerebrospinal fluid in the pathogenesis of CNS infections.

MSC: Analyzing 14. Using the table below, which patient is most likely infected by a bacterium?

a. b. c. d.

Patient A Patient B Patient C None of these patients are likely to be infected by a bacterium.

ANS: B DIF: Moderate REF: 24.2 OBJ: 24.2b Use key laboratory information to distinguish types of CNS infections.

MSC: Applying 15. What is labeled as “C” in the figure below?

a. acetylcholine b. toxin

c. motor neuron d. muscle

ANS: A DIF: Easy REF: 24.4 OBJ: 24.4c List patient history information and clinical signs and symptoms specific to each bacterial pathogen of the central nervous system.

MSC: Applying 16. Bacterial encephalitis and meningitis are difficult to treat because a. no medications exist for treatment of these infections.

b. antibiotics damage nervous tissue. c. many antibiotics cannot cross the blood–brain barrier. d. it is very difficult to determine the causative microbe.

ANS: C DIF: Easy REF: 24.1 OBJ: 24.1d Correlate the anatomy of the central nervous system to the symptoms of CNS infections.

MSC: Understanding 17. Which of the following statements about rabies is FALSE? a. It is caused by lyssavirus. b. Rabies virus is a neurotropic virus. c. Hydrophobia is associated with the disease. d. There are three basic forms: encephalitic, paralytic, and atypical.

ANS: B DIF: Moderate REF: 24.3 OBJ: 24.3c Outline clinical diagnoses of viral CNS infections according to the patient’s history, signs, and symptoms.

MSC: Remembering 18. Viral diseases of the central nervous system are transmitted by all of the following EXCEPT a. sexual contact. c. the fecal-oral route. b. mosquito bites. d. stepping on a contaminated nail.

ANS: D DIF: Easy REF: 24.3 OBJ: 24.3b Explain the role of reservoirs in pathogenesis and prevention of viral diseases of the central nervous system.

MSC: Understanding 19. Vaccination is available for all the following EXCEPT a. meningitis. c. rabies. b. tetanus. d. botulism.

ANS: D DIF: Easy REF: 24.4 OBJ: 24.4d Relate pathogenesis of bacterial CNS diseases to prevention and treatment modalities used.

MSC: Remembering 20. Which of the following vaccines can cause the disease it is designed to prevent? a. tetanus toxoid c. inactivated polio b. oral polio d. meningococcal capsule ANS: B DIF: Moderate REF: 24.3 OBJ: 24.3d Recommend treatment and prevention options for different viral CNS infections.

MSC: Understanding 21. All of the following are true of polio EXCEPT a. the portal of entry is ingestion of contaminated water. b. most cases are severe and result in paralysis. c. it replicates in the throat and small intestines. d. the Sabin vaccine contains attenuated strains of the virus.

ANS: B DIF: Moderate REF: 24.3 OBJ: 24.3b Explain the role of reservoirs in pathogenesis and prevention of viral diseases of the central nervous system.

MSC: Understanding 22. All of the following are true of Neisseria meningitides EXCEPT a. the capsule protects the organism from host complement proteins. b. it does not cross the blood–brain barrier. c. the organism uses type IV pili to invade epithelial cells.

d. it produces a nonblanching rash due to endotoxin release.

ANS: B DIF: Difficult REF: 24.4 OBJ: 24.4b Describe how different bacteria overcome host defenses to cause CNS disease.

MSC: Analyzing 23. Which of the following is a fungus that causes CNS disease? a. C. albicans c. T. brucei b. T. gondii d. C. tetani ANS: A DIF: Easy REF: 24.5 OBJ: 24.5a Name fungi that cause CNS disease.

MSC: Remembering

24. Fungal infections of the CNS are most commonly seen in a. immunocompetent individuals. c. AIDS patients. b. young, healthy individuals. d. newborns.

ANS: C DIF: Moderate REF: 24.5 OBJ: 24.5b Describe the role of host immunity in fungal infections of the CNS. MSC: Understanding 25. Which of the images below is the amebic form that infects humans?

a. A b. B

c. C d. None of these infect humans.

ANS: B DIF: Moderate REF: 24.5 OBJ: 24.5c Define fungal CNS infections in the context of environmental exposure risks.

MSC: Applying 26. All of the following are true regarding African trypanosomiasis EXCEPT that a. it is also known as “sleeping sickness.” b. all subspecies of Trypanosoma brucei have multiple hosts. c. it is transmitted by the tsetse fly. d. death occurs without proper treatment.

ANS: B DIF: Easy REF: 24.6 OBJ: 24.6a Compare and contrast parasites and prions.

MSC: Remembering

27. What is the prescribed treatment for Naegleria? a. ketoconazole c. penicillin b. eflornithine d. vaccine ANS: A DIF: Easy REF: 24.6 OBJ: 24.6d Name prevention and treatment options for parasitic and prion CNS disease.

MSC: Remembering 28. Which of the following is true about Candida albicans? a. Normal flora helps this organism to cause disease. b. It commonly causes disease in immunocompetent individuals.

c. Treatment includes amphotericin B and flucytosine. d. Candida meningitis is seen more commonly in teenagers.

ANS: C DIF: Moderate REF: 24.5 OBJ: 24.5d Identify diagnostic methods and treatment options for different fungal CNS infections.

MSC: Understanding 29. Which of the following statements about prions is correct? a. Prions are small particles that contain DNA. b. Chemical agents easily destroy prions. c. Acanthamoeba encephalitis is caused by prions. d. Prions can be transmitted via contaminated food.

ANS: D DIF: Moderate REF: 24.6 OBJ: 24.6c Explain the role of host immune responses in parasitic and prion CNS disease.

MSC: Understanding 30. This figure below shows an India ink stain of C. neoformans in a patient’s CSF. What is the purpose of the capsule depicted by the arrow?

a. b. c. d.

It protects the organism from the host immune response.

It allows the organism to spread to the CNS. The capsule causes the persistent headache seen in most cases of coccidioidal meningitis.

It is targeted by fluconazole as a treatment.

ANS: A DIF: Moderate REF: 24.6 OBJ: 24.6c Explain the role of host immune responses in parasitic and prion CNS disease.

MSC: Applying 31. Dennis, a 50-year-old man, was hospitalized with dizziness, blurred vision, slurred speech, difficulty swallowing, and nausea. Examination revealed facial paralysis. He reported eating home-canned green beans 24 hours before the onset of his symptoms. Dennis should first be treated with a. antibiotics. c. toxins. b. vaccination. d. antitoxins.

ANS: D DIF: Moderate REF: 24.4 OBJ: 24.4c List patient history information and clinical signs and symptoms specific to each bacterial pathogen of the central nervous system.

MSC: Applying 32. Which of the following protozoan(s) use antigenic switching to avoid the host immune system?

a. T. gondii b. T. brucei

c. T. cruzi d. T. brucei and T. cruzi

ANS: D DIF: Easy REF: 24.6 OBJ: 24.6c Explain the role of host immune responses in parasitic and prion CNS disease.

MSC: Remembering 33. A pathologist detects Negri bodies while examining a brain section taken at autopsy. What was the cause of death? a. rabies c. spongiform encephalopathy b. poliomyelitis d. West Nile encephalitis ANS: A DIF: Easy REF: 24.3 OBJ: 24.3c Outline clinical diagnoses of viral CNS infections according to the patient’s history, signs, and symptoms.

MSC: Applying 34. In the figure below, where does botulinum toxin act to prevent acetylcholine release?

a. dendrite b. Schwann cell

c. axon d. axon terminal

ANS: D DIF: Moderate REF: 24.4 OBJ: 24.4b Describe how different bacteria overcome host defenses to cause CNS disease.

MSC: Applying 35. Which part of the neuron shown below receives information from the periphery?

a. dendrite b. Schwann cell

c. axon d. axon terminal

ANS: A DIF: Easy REF: 24.1 OBJ: 24.1a Describe the functional organization of the central nervous system.

MSC: Applying 36. Victoria, a 30-year-old woman, was hospitalized after she experienced convulsions. On examination, she was alert and oriented and complained of a fever, headache, and stiff neck. Which of the following is most likely to provide rapid identification of the cause of Victoria’s symptoms? a. Gram stain of cerebrospinal fluid c. biopsy of brain tissue b. Gram stain of throat culture d. checking serum antibodies ANS: A DIF: Easy REF: 24.4 OBJ: 24.4a Identify risk factors for each of the bacterial CNS diseases.

MSC: Understanding 37. A physician diagnoses a patient with Eastern equine encephalitis. All of the following pertain to the patient EXCEPT that he or she a. most likely contracted the virus through a bite from an infected mosquito. b. was diagnosed by detecting an increase in antibody titer to the virus. c. is infected with a neurotropic virus. d. is infected with a rare disease.

ANS: C DIF: Moderate REF: 24.3 OBJ: 24.3c Outline clinical diagnoses of viral CNS infections according to the patient’s history, signs, and symptoms.

MSC: Understanding 38. Arboviruses cause ________ and are transmitted by ________. a. meningitis; bee stings c. encephalitis; dog bites b. meningitis; mosquitoes d. encephalitis; mosquitoes ANS: D DIF: Easy REF: 24.3 OBJ: 24.3a Classify viral CNS infections by their mode of transmission.

MSC: Understanding

39. Which of the following is treated with antibiotics? a. botulism c. streptococcal pneumonia b. tetanus d. polio ANS: C DIF: Moderate REF: 24.3 OBJ: 24.3d Recommend treatment and prevention options for different viral CNS infections.

MSC: Understanding 40. Which of the following pairs is mismatched? a. poliomyelitis—respiratory route b. meningococcal meningitis—respiratory route c. rabies—direct contact d. listeriosis—ingestion ANS: B DIF: Easy REF: 24.3 OBJ: 24.3a Classify viral CNS infections by their mode of transmission.

MSC: Applying 41. CASE HISTORY In April 2001, Abdul, a four-month-old infant from Saudi Arabia, was hospitalized with fever, tender neck, and purplish, nonblanching spots (petechiae and purpuric spots) on his trunk. Suspecting meningitis, the clinician took a CSF sample and examined it by Gram stain. The smear revealed Gram-negative diplococci inside PMNS. The CSF was turbid with 900 leukocytes/l, and Neisseria meningitidis was confirmed by culture. The child was treated with cefotaxime and made a full recovery. His father, the person who brought him in, was clinically well. However, meningococcus was isolated from his oropharynx, as well as from the throat of the patient’s two-year-old brother.

Isolates from the patient, his father, and his brother were positive by agglutination with meningococcus a, c, y, W135 polyvalent reagent. The father’s vaccination certificate confirmed that he had received a quadrivalent meningococcal vaccine. All three isolates were sent to the World Health Organization collaborating center, which confirmed meningococcus serogroup W135. DNA analysis of the three isolates found them to be indistinguishable, meaning that the father and his children were infected with the same strain of N. meningitidis.

Which of the following statements is INCORRECT regarding the pathogenesis and prevention of Abdul’s meningitis? a. N. meningitidis generally only infects infants, explaining why Abdul’s father and brother showed no symptoms of disease. b. Ten to twenty percent of the healthy population can be colonized by N. meningitidis and remain asymptomatic. c. Complement deficiencies make individuals particularly susceptible to meningococcal meningitis. d. N. meningitidis utilized type IV pili to disrupt tight junctions, allowing passage through the blood–brain barrier.

ANS: A DIF: Moderate REF: Case History 24.2 OBJ: 24.4a Identify risk factors for each of the bacterial CNS diseases.

MSC: Understanding COMPLETION 1. The ________ collects data from the outside environment and communicates that information to the ________.

ANS: peripheral nervous system; central nervous system

DIF: Moderate REF: 24.1 OBJ: 24.1a Describe the functional organization of the central nervous system.

MSC: Understanding 2. Inflammation of the meninges is called ________, while inflammation of the brain is called ________.

ANS: meningitis; encephalitis DIF: Easy REF: 24.2 OBJ: 24.2c Compare and contrast the roles of meninges and cerebrospinal fluid in the pathogenesis of CNS infections. MSC: Understanding 3. One of the complications of poliomyelitis is damage to the ________ nerve, which interferes with breathing.

ANS: phrenic DIF: Moderate REF: 24.3 OBJ: 24.3c Outline clinical diagnoses of viral CNS infections according to the patient’s history, signs, and symptoms.

MSC: Remembering 4. Fungal infections of the central nervous system are also known as ________.

ANS: mycoses DIF: Easy REF: 24.5 MSC: Remembering

OBJ: 24.5a Name fungi that cause CNS disease.

5. A small proteinaceous infectious particle is known as a ________.

ANS: prion DIF: Easy REF: 24.6 MSC: Remembering

OBJ: 24.6a Compare and contrast parasites and prions.

SHORT ANSWER 1. Discuss the advantages and disadvantages of the Salk and Sabin vaccines.

ANS: Two types of polio vaccines exist. Jonas Salk developed the first polio vaccine, which contains inactivated forms of all three serotypes of poliovirus. The inactivated vaccine does not contain active virus and must be injected for immunity to develop.

The second vaccine, developed by Albert Sabin, is a live attenuated vaccine that contains mutated forms of all three serotypes. The Sabin vaccine is given orally, which affords these mutated viruses a chance to replicate in intestinal cells and generate a more natural immunity. Unfortunately, attenuated viruses can, at times, revert to their active virulent form. This results in vaccine-associated paralytic poliomyelitis (VAPP).

DIF: Difficult REF: 24.3 OBJ: 24.3d Recommend treatment and prevention options for different viral CNS infections.

MSC: Evaluating

2. The figure below shows the mechanism of action of botulinum toxin. Describe what is happening in each step.

ANS: The botulinum toxin enters at the peripheral nerve end where the nerve meets muscle (the neuromuscular junction). The toxin binds to target membranes and is brought into the cell by endocytosis. The low pH that forms in the endosome cleaves the disulfide bonds holding the two halves of the toxin together; a channel is assembled through the membrane, and the light chain (toxin) is released into the cytoplasm. The toxic subunit then cleaves key host proteins involved in the exocytosis of vesicles containing neurotransmitters, disrupting the release of neurotransmitters and causing disease.

DIF: Difficult REF: 24.4 OBJ: 24.4c List patient history information and clinical signs and symptoms specific to each bacterial pathogen of the central nervous system.

MSC: Applying 3. Describe what is happening in the figure below’s depiction of retrograde movement of tetanus toxin.

ANS:

Tetanus toxin enters the nervous system at the neuromuscular junction and travels up the axon to an inhibitory neuron of the central nervous system. There the toxin cleaves proteins associated with exocytosis of vesicles containing inhibitory neurotransmitters. In the absence of inhibitory signals, excitatory signals that stimulate muscle contraction prevail.

1. The bacterium C. tetani releases toxin.

2. The toxin then travels along the neuron axon.

3. The toxin blocks inhibitory neurotransmitters.

DIF: Difficult REF: 24.4 OBJ: 24.4b Describe how different bacteria overcome host defenses to cause CNS disease.

MSC: Applying 4. Explain the transmission, etiologies, and diagnosis of bacterial meningitis.

ANS: Bacterial meningitis is considered a medical emergency. Patient history can provide clues, but laboratory results are needed for definitive diagnosis. Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae type b are the top causative agents of meningitis.

Neisseria meningitidis affects people of all ages; however, it severely targets adolescents and young adults. It is transmitted from the nasopharynx of infected individuals. Diagnosis is based off clinical presentation, isolation of the bacteria from CSF, and/or blood and Gram stain of CSF. Streptococcus pneumoniae affects people of all ages and is transmitted via the respiratory tract.

Diagnosis is based off clinical presentation, CSF analysis, bacterial culture, and Gram stain.

Haemophilus influenzae affects unvaccinated adults and children and is transmitted from the upper respiratory tract. Diagnosis is based off clinical presentation, CSF analysis, blood culture, and Gram stain.

DIF: Difficult REF: 24.2 OBJ: 24.2a Categorize central nervous system infections by the anatomical structures affected.

MSC: Applying 5. List and describe the defensive mechanisms that are in place to protect the central nervous system.

ANS: The CNS is protected from most harm by several mechanisms.

1. Skull and vertebrae are physical barriers to trauma.

2. Meninges are membranes that separate the brain and the spinal cord from the bony structure surrounding them. There are three layers: pia mater, arachnoid mater, and dura mater. The choroid plexus located inside the pia mater secretes cerebrospinal fluid into the subarachnoid space.

3. The blood–brain barrier prevents most microorganisms from gaining access to the CNS. The specialized junctions prevent bacteria from moving out of the circulating blood and into the CSF. DIF: Difficult REF: 24.1 OBJ: 24.1b Explain how meninges and cerebrospinal fluid protect the central nervous system.

MSC: Analyzing 6. CASE HISTORY

In June, Mitch, a 47-year-old resident of Oklahoma, was admitted to the hospital with rapid onset of progressive dizziness, blurred vision, slurred speech, difficulty swallowing, and nausea. Findings on examination included absence of fever, drooping eyelids, facial paralysis, and impaired gag reflex. He developed breathing difficulties and required mechanical ventilation. The patient reported that during the 24 hours before onset of symptoms, he had eaten home-canned green beans and a stew containing roast beef and potatoes. Analysis of the patient’s stool detected botulinum type a toxin, but no Clostridium botulinum organisms were found. The patient was hospitalized for 49 days, including 42 days on mechanical ventilation, before being discharged.

Briefly describe the likely progress of Mitch’s disease from exposure to hospitalization. Is antibiotic therapy likely to be useful in the treatment of Mitch’s disease? Why or why not?

ANS: It was likely through consumption of food that the toxin had been produced, rather than through infection. Antibiotics will not treat intoxication without infection.

DIF: Moderate REF: Case History 24.3 OBJ: 24.4d Relate pathogenesis of bacterial CNS diseases to prevention and treatment modalities used. MSC: Analyzing 7. CASE HISTORY In June, Mitch, a 47-year-old resident of Oklahoma, was admitted to the hospital with rapid onset of progressive dizziness, blurred vision, slurred speech, difficulty swallowing, and nausea. Findings on examination included absence of fever, drooping eyelids, facial paralysis, and impaired gag reflex. He developed breathing difficulties and required mechanical ventilation. The patient reported that during the 24 hours before onset of symptoms, he had eaten home-canned green beans and a stew containing roast beef and potatoes. Analysis of the patient’s stool detected botulinum type a toxin, but no Clostridium botulinum organisms were found. The patient was hospitalized for 49 days, including 42 days on mechanical ventilation, before being discharged.

What are the risk factors for botulism like that in Mitch’s case? How can this disease be prevented?

ANS: Individual risk factors are largely irrelevant in the contraction of intoxication botulism. Consumption of improperly (home) canned foods is often implicated. Proper canning and cooking are paramount.

An effective vaccine does not exist.

DIF: Moderate REF: Case History 24.3 OBJ: 24.4a Identify risk factors for each of the bacterial CNS diseases.

MSC: Understanding

Chapter 25: Diagnostic Clinical Microbiology LEARNING OBJECTIVES 25.1a List the reasons for identifying the cause of an infectious disease.

25.1b Explain the basic epidemiologic purpose of identifying the cause of an infectious disease.

25.2a Identify sterile and nonsterile body sites.

25.2b List procedures and precautions used to collect specimens from sterile body sites.

25.2c List procedures used to collect specimens from body sites containing normal microbiota.

25.3a Explain how biochemical profiles can be used to identify microbial pathogens.

25.3b Discuss the major biochemical features that broadly differentiate Gram-negative and Gram-positive pathogens.

25.3c Describe the Lancefield classification and its importance to clinical microbiology.

25.3d Explain the difference between selective and differential media and their use in clinical microbiology.

25.3e Discuss differences between the acid-fast stain and Gram stain.

25.4a Discuss how the polymerase chain reaction can be used to identify pathogens in a clinical sample and the role of real-time PCR in clinical diagnosis.

25.4b List the advantages and disadvantages of PCR, restriction fragment length polymorphisms, and biochemical strategies of pathogen identification.

25.5a Describe how enzyme-linked immunosorbent assays can identify microbial antigens present in clinical samples or antimicrobial antibodies present in serum.

25.5b Discuss the fluorescent antibody staining technique.

25.6a Differentiate between assay specificity and sensitivity.

25.6b Explain the basic immunochromatography assay used in point-of-care diagnostic kits.

25.6c Discuss the advantages and disadvantages of point-of-care diagnostics.

MULTIPLE CHOICE 1. Identifying infectious agents is important because a. it costs less money to run numerous tests than to treat with antibiotics empirically. b. antibiotic-resistant bacteria are becoming a major global threat. c. pathogens must be identified before antibiotics are effective. d. antibiotics are only effective against viruses.

ANS: B DIF: Easy REF: 25.1 OBJ: 25.1a List the reasons for identifying the cause of an infectious disease.

MSC: Understanding 2. How does identifying the cause of an infectious disease help prevent the development of antibioticresistant bacteria? a. Knowing the identity and properties of the causative agent allows targeting with an appropriate drug. b. Treating bacterial infections with multiple antibiotics helps prevent the development of antibiotic-resistant bacteria. c. Knowing the identity and properties of the causative agent allows a physician to empirically treat an infection. d. Treating viral infections with multiple antibiotics helps prevent secondary infections caused by antibiotic-resistant bacteria.

ANS: A DIF: Difficult REF: 25.1 OBJ: 25.1a List the reasons for identifying the cause of an infectious disease.

MSC: Analyzing 3. Twenty-five individuals with shigellosis are reported within a community. Which of the following pieces of information would be most useful to public health officials who are trying to stop the spread of this infection? a. whether all individuals are infected with the same strain of bacteria b. the antibiotic sensitivity of the causative agents c. the complete health history of infected individuals d. the day care centers attended by any children of infected individuals ANS: A DIF: Moderate REF: 25.1 OBJ: 25.1b Explain the basic epidemiologic purpose of identifying the cause of an infectious disease.

MSC: Applying 4. Which of the following is considered to be a sterile body site? a. cerebrospinal fluid c. urethra b. nasopharynx d. large intestine ANS: A DIF: Easy REF: 25.2 OBJ: 25.2a Identify sterile and nonsterile body sites.

MSC: Remembering

5. Which of the following samples would be expected to be free of microorganisms unless an infection is present? a. blood c. nasopharyngeal swab b. fecal stool sample d. urethral swab ANS: A DIF: Easy REF: 25.2 OBJ: 25.2a Identify sterile and nonsterile body sites.

MSC: Understanding

6. Which of the following samples would be expected to contain normal microbiota? a. peritoneal fluid c. blood b. cerebrospinal fluid d. fecal stool sample ANS: D DIF: Easy REF: 25.2 OBJ: 25.2a Identify sterile and nonsterile body sites.

MSC: Remembering

7. Which of the following samples would be LEAST likely to require anaerobic incubation? a. nasopharyngeal swab c. blood b. cerebrospinal fluid d. synovial fluid ANS: D DIF: Easy REF: 25.2 OBJ: 25.2b List procedures and precautions used to collect specimens from sterile body sites.

MSC: Applying 8. Which of the following would typically be the initial indicator of bacteria growing within a blood culture tube? a. An automated incubator will detect fluorescence. b. Bacterial colonies will appear on blood agar. c. Bacterial colonies will appear on MacConkey agar. d. Centrifugation will cause sediment to appear at the end of the tube.

ANS: A DIF: Moderate REF: 25.2 OBJ: 25.2b List procedures and precautions used to collect specimens from sterile body sites.

MSC: Understanding 9. Lumbar puncture is the most common method for obtaining a sample of a. blood. c. synovial fluid. b. cerebrospinal fluid. d. peritoneal fluid.

ANS: B DIF: Easy REF: 25.2 OBJ: 25.2b List procedures and precautions used to collect specimens from sterile body sites.

MSC: Understanding 10. José is seen for a draining abscess on his left forearm. Which of the following would most likely be used to collect a sample from this site? a. needle aspiration c. sputum sample b. skin scraping d. swab ANS: D DIF: Easy REF: 25.2 OBJ: 25.2c List procedures used to collect specimens from body sites containing normal microbiota.

MSC: Understanding 11. A lab technician intern is asked to apply a 10% KOH (potassium hydroxide) solution on a sample.

There are four patient samples sitting on the lab bench and he is trying to remember which sample should be treated. The sample that would require treatment with KOH would be a a. skin scraping from a site suspected to be a fungal infection. b. nasopharyngeal swab suspected of containing Bordetella pertussis. c. sputum sample from a patient with tuberculosis. d. fecal sample from an individual with bloody diarrhea.

ANS: A DIF: Difficult REF: 25.2 OBJ: 25.2c List procedures used to collect specimens from body sites containing normal microbiota.

MSC: Analyzing 12. In which of the following scenarios would selective media most likely be used to DECREASE the number of normal microbiota? a. A nasopharyngeal swab is used to collect a sample from a young woman with inflamed tonsils. b. A midstream clean catch is used to collect urine from a young woman with a suspected urinary tract infection. c. Venipuncture is used to collect blood from an elderly man with a possible blood infection. d. A lumbar puncture is used to collect cerebrospinal fluid from a toddler exhibiting signs of meningitis.

ANS: A DIF: Moderate REF: 25.2 OBJ: 25.2c List procedures used to collect specimens from body sites containing normal microbiota.

MSC: Evaluating 13. A young child arrives at a local hospital with neck stiffness, nausea, and vomiting. The attending physician suspects bacterial meningitis and sends a sample of cerebrospinal fluid to the hospital laboratory. To most quickly identify the bacterial species, the laboratory technician should a. use sequential biochemical tests in which each test dictates the next test. b. carry out a series of tests simultaneously and then interpret the tests sequentially. c. plate the species first on selective media to eliminate the number of normal microbiota. d. obtain a sequence of the patient’s genome to determine his or her susceptibility to specific microbes.

ANS: B

DIF: Difficult

REF: 25.3

OBJ: 25.3a Explain how biochemical profiles can be used to identify microbial pathogens.

MSC: Analyzing 14. The figure below illustrates a small portion of an algorithm used to identify Gram-negative rods. This diagram is referred to as a(n)

a. dichotomous key. b. API 20E reading.

c. selective algorithm. d. binary test.

ANS: A DIF: Easy REF: 25.3 OBJ: 25.3a Explain how biochemical profiles can be used to identify microbial pathogens.

MSC: Remembering 15. How are API strips inoculated with a bacterium interpreted? a. Strips with positive reactions for each test indicate a bacterium is Gram negative. b. Strips with positive reactions for each test indicate a bacterium is Gram positive. c. Lab personnel interpret strips by using a dichotomous key and beginning with a key reaction. d. Lab personnel interpret strips by determining the pH of each individual well.

ANS: C DIF: Difficult REF: 25.3 OBJ: 25.3a Explain how biochemical profiles can be used to identify microbial pathogens.

MSC: Applying 16. Which of the following organisms would be able to grow on both blood agar and Hektoen agar plates? a. Streptococcus pneumoniae c. Staphylococcus epidermidis b. Escherichia coli d. Streptococcus pyogenes ANS: B DIF: Difficult REF: 25.3 OBJ: 25.3b Discuss the major biochemical features that broadly differentiate Gram-negative and Gram-positive pathogens.

MSC: Applying 17. A nasopharyngeal swab is used to isolate a Gram-positive coccus. Tests reveal the organism produces bubbles when a colony is mixed with H2O2 and converts fibrinogen into fibrin to produce a coagulated tube of plasma. Using the figure shown below, the organisms can be identified as

a. Streptococcus pneumoniae. b. Streptococcus pyogenes.

c. Staphylococcus epidermidis. d. Staphylococcus aureus.

ANS: D DIF: Moderate REF: 25.3 OBJ: 25.3b Discuss the major biochemical features that broadly differentiate Gram-negative and Gram-positive pathogens.

MSC: Applying 18. A swab from an infected lesion is streaked onto a blood agar plate, a plate with blood agar that also contains colistin and nalidixic acid (a CNA plate), and a MacConkey agar plate. Growth occurs on both the blood agar and CNA plates. The organism growing must be a. Gram positive. c. Gram negative, nonenteric. b. Gram negative, enteric. d. acid-fast.

ANS: A DIF: Moderate REF: 25.3 OBJ: 25.3b Discuss the major biochemical features that broadly differentiate Gram-negative and Gram-positive pathogens.

MSC: Applying 19. Streptococcus pyogenes is a medically significant member of the Lancefield group a. A. c. C. b. B. d. D. ANS: A DIF: Easy REF: 25.3 OBJ: 25.3c Describe the Lancefield classification and its importance to clinical microbiology.

MSC: Remembering 20. The algorithm shown below indicates bacitracin sensitivity for only one group of Gram-positive cocci.

Why is bacitracin sensitivity NOT tested in all of the cases shown?

a. Testing antibiotic sensitivity in nonhemolytic streptococci is too time-consuming. b. All group A beta-hemolytic streptococci are bacitracin sensitive. c. Only beta-hemolytic streptococci possess characteristics that make them sensitive to bacitracin. d. Nonhemolytic and alpha-hemolytic bacteria are only susceptible to optochin.

ANS: B DIF: Moderate REF: 25.3 OBJ: 25.3c Describe the Lancefield classification and its importance to clinical microbiology.

MSC: Analyzing 21. A sample of bacteria is plated on Hektoen agar. Growth is observed and the medium changes to an orange color. The given information indicates that the organism ferments ________ and is Gram ________. a. lactose; positive c. lactose; negative b. sucrose; positive d. sucrose; negative ANS: C DIF: Moderate REF: 25.3 OBJ: 25.3d Explain the difference between selective and differential media and their use in clinical microbiology.

MSC: Understanding 22. A researcher wants to isolate Gram-negative bacteria from Gram-positive bacteria and is not interested in biochemical differences between the Gram-negative bacteria. It would be best for the researcher to use a growth media that is a. selective. c. selective and differential. b. differential. d. nonselective.

ANS: A DIF: Easy REF: 25.3 OBJ: 25.3d Explain the difference between selective and differential media and their use in clinical microbiology.

MSC: Applying 23. Eosin methylene blue (EMB) agar contains dyes that inhibit the growth of Gram-positive organisms and bile salts that prevent the growth of Gram-negative bacteria other than fecal coliforms. Also included in EMB are stains that show a color change when an organism ferments lactose. This media is best described as a. selective. c. selective and differential. b. differential. d. nonselective.

ANS: C DIF: Moderate REF: 25.3 OBJ: 25.3d Explain the difference between selective and differential media and their use in clinical microbiology.

MSC: Applying 24. Organisms will resist Gram staining when they contain a waxy outer coat composed of a. peptidoglycan. c. lipopolysaccharide. b. mycolic acid. d. cellulose.

ANS: B DIF: Moderate REF: 25.3 OBJ: 25.3e Discuss differences between the acid-fast stain and Gram stain.

MSC: Remembering 25. What advantage does real-time PCR provide over tissue culture identification methods when a patient is infected by a virus such as West Nile virus? a. Antibodies can be rapidly detected in body fluids. b. The virus itself can be detected in body fluids. c. The source of the virus can be traced. d. The patient’s antibody response can be measured in real time.

ANS: B DIF: Moderate REF: 25.4 OBJ: 25.4a Discuss how the polymerase chain reaction can be used to identify pathogens in a clinical sample and the role of real-time PCR in clinical diagnosis.

MSC: Applying 26. The image shown below is a gel from a multiplex polymerase chain reaction (PCR) used to identify toxin genes in Clostridium botulinum. Which of the following statements most accurately describes how this image was formed?

a. b. c. d.

An amplified sample of DNA was combined with four sets of PCR primers.

Four patient samples were combined with one set of PCR primers.

A thermocycler was used to run four separate PCR amplification cycles.

A patient sample was combined with four sets of PCR primers.

ANS: D DIF: Difficult REF: 25.4 OBJ: 25.4a Discuss how the polymerase chain reaction can be used to identify pathogens in a clinical sample and the role of real-time PCR in clinical diagnosis.

MSC: Analyzing 27. The image shown below is a gel from a multiplex polymerase chain reaction (PCR) used to identify toxin genes in Clostridium botulinum. Why are there three lines associated with the patient shown?

a. The patient is infected by three different species of bacteria. b. Restriction fragments cut the patient DNA sample into three fragments. c. The patient is infected by a strain of Clostridium botulinum that contains three toxin genes. d. Molecular beacon probes are causing fluorescence of three regions.

ANS: C DIF: Difficult REF: 25.4 OBJ: 25.4a Discuss how the polymerase chain reaction can be used to identify pathogens in a clinical sample and the role of real-time PCR in clinical diagnosis.

MSC: Analyzing 28. Biochemical tests would most likely be used to diagnose a. whooping cough. c. HIV. b. strep throat. d. Lyme disease.

ANS: B DIF: Moderate REF: 25.4 OBJ: 25.4b List the advantages and disadvantages of PCR, restriction fragment length polymorphisms, and biochemical strategies of pathogen identification.

MSC: Applying 29. Of the molecular techniques listed below, which would be most useful in identifying whether patients infected by Mycobacterium tuberculosis are part of the same outbreak? a. real-time PCR b. biochemical tests c. multiplex PCR d. restriction fragment length polymorphism (RFLP) ANS: D DIF: Moderate REF: 25.4 OBJ: 25.4b List the advantages and disadvantages of PCR, restriction fragment length polymorphisms, and biochemical strategies of pathogen identification.

MSC: Applying 30. An advantage of using polymerase chain reaction (PCR) instead of relying on biochemical tests is that PCR a. can be completed within hours instead of days. b. provides a conclusive identification of a bacterium. c. provides information about antibiotic sensitivity. d. does not require specialized equipment.

ANS: A DIF: Easy REF: 25.4 OBJ: 25.4b List the advantages and disadvantages of PCR, restriction fragment length polymorphisms, and biochemical strategies of pathogen identification.

MSC: Understanding 31. The figure shown below illustrates antigen-capture ELISA. The structure labeled A in this figure is a(n)

a. monoclonal antibody. b. antigen.

c. enzyme-conjugated antibody. d. ELISA molecule.

ANS: C DIF: Easy REF: 25.5 OBJ: 25.5a Describe how enzyme-linked immunosorbent assays can identify microbial antigens present in clinical samples or antimicrobial antibodies present in serum.

MSC: Understanding 32. The figure shown below illustrates antigen-capture ELISA. An advantage of this technique over antibody-capture ELISA is that antigen-capture ELISA

a. b. c. d.

leads to a speedier diagnosis. is more accurate than antibody-capture. does not use serum from infectious patients. provides a quantitative measure of patient antibody levels.

ANS: A DIF: Moderate REF: 25.5 OBJ: 25.5a Describe how enzyme-linked immunosorbent assays can identify microbial antigens present in clinical samples or antimicrobial antibodies present in serum.

MSC: Understanding 33. Identification of the antigenic type(s) of Streptococcus pneumoniae in two patients with pneumonia is useful in a. determining the appropriate antibiotic treatment. b. determining whether the patients are producing antibodies.

c. identifying the source of the bacterium. d. identifying whether the bacterium will grow easily in a laboratory.

ANS: C DIF: Moderate REF: 25.5 OBJ: 25.5b Discuss the fluorescent antibody staining technique.

MSC: Understanding 34. Which of the following is most likely to be recognized by a fluorescent antibody? a. nucleus c. cytoplasm b. cell membrane d. capsule ANS: D DIF: Easy REF: 25.5 OBJ: 25.5b Discuss the fluorescent antibody staining technique.

MSC: Remembering 35. This figure below shows a newly developed immunochromatography test (ICT) for anti-Ebola antibodies. The three individuals tested are known to NOT have Ebola. What information does the sample of tests shown give you?

a. b. c. d.

The sensitivity of the test is low because a false positive is shown on one test.

The specificity of the test is low because a false positive is shown on one test.

The sensitivity of the test is high because a false positive is shown on one test.

The sensitivity and specificity cannot be determined from a small sample size.

ANS: D DIF: Moderate REF: 25.6 OBJ: 25.6a Differentiate between assay specificity and sensitivity.

MSC: Analyzing 36. One immunochromatography test (ICT) for influenza has a test sensitivity of 0.50 and a specificity of 0.90. If 50 individuals known to be infected with influenza were tested using this particular ICT, how many of the tests would be expected to be false negatives? a. 25 c. 45 b. 50 d. 10 ANS: A DIF: Difficult REF: 25.6 OBJ: 25.6a Differentiate between assay specificity and sensitivity.

MSC: Applying 37. If red colloidal gold particles were inadvertently left out of a batch of immunochromatographic assays known to have a sensitivity of 0.99 for HIV, which of the following would most likely occur when testing patients infected with HIV? a. Neither a test line nor a control line would be present. b. Only a test line would be present.

c. Only a control line would be present. d. Both a test line and a control line would be present.

ANS: A DIF: Moderate REF: 25.6 OBJ: 25.6b Explain the basic immunochromatography assay used in point-of-care diagnostic kits.

MSC: Applying 38. What is the function of goat anti-rabbit IgG antibodies in a typical point-of-care immunochromatographic assay? a. In the absence of antibodies in a clinical specimen, they bind to red colloidal gold particles. b. They are conjugated with red colloidal gold particles and are used to bind to antigen in a clinical specimen. c. In the presence of antigen in a clinical specimen, they prevent complexes from forming with rabbit antibodies. d. In the absence of antigen in a clinical specimen, they bind rabbit antibodies attached to red colloidal gold particles.

ANS: D DIF: Moderate REF: 25.6 OBJ: 25.6b Explain the basic immunochromatography assay used in point-of-care diagnostic kits.

MSC: Understanding 39. An advantage of a point-of-care (POC) test is that a. laboratory technicians have a lower risk of exposure to pathogens. b. clinicians are able to diagnose diseases based on clinical signs and symptoms alone. c. antibiotic therapy can begin without a delay of waiting for off-site laboratory results. d. detection of multiple infections is more likely.

ANS: C DIF: Easy REF: 25.6 OBJ: 25.6c Discuss the advantages and disadvantages of point-of-care diagnostics.

MSC: Understanding 40. A disadvantage of a point-of-care (POC) test is that a. technicians are not required to culture the pathogen. b. clinicians are able to rapidly recognize a chain of infection. c. antibiotics can be avoided in cases of viral infection. d. multiple infections are more likely to go undetected.

ANS: D DIF: Easy REF: 25.6 OBJ: 25.6c Discuss the advantages and disadvantages of point-of-care diagnostics.

MSC: Understanding 41. CASE HISTORY A four-year-old boy, Evan, was admitted to the hospital to evaluate and treat persistent pain in the rectal area. His problem began about one week earlier with ill-defined pain in the same region. He had a white blood cell count of 24,900 with 87% granulocytes (neutrophils). An abdominal computed tomography scan revealed an abscess (walled-off region of infectious bacteria) next to his rectum. A needle aspiration of the abscess drained 20 milliliters of yellowish, foul-smelling fluid. The specimen was plated on blood agar under aerobic conditions, but the culture was negative despite evidence of bacteria in the abscess drainage. (Blood agar is a rich medium containing 5% sheep red blood cells.)

Which statement regarding specimen collection is FALSE? a. Specimen collection procedures are generally divided into those for sterile and nonsterile body sites. b. Internal abscesses should be collected under conditions that allow the survival of

anaerobic pathogens. c. Samples from both sterile and nonsterile body sites should be plated on selective media. d. Sterile body site samples are easily contaminated by normal flora in the collection process.

ANS: C DIF: Moderate REF: Case History 25.1 OBJ: 25.2b List procedures and precautions used to collect specimens from sterile body sites. | 25.2c List procedures used to collect specimens from body sites containing normal microbiota.

MSC: Understanding COMPLETION 1. Body sites that contain no microorganisms are considered to be ________.

ANS: sterile DIF: Easy REF: 25.2 MSC: Remembering

OBJ: 25.2a Identify sterile and nonsterile body sites.

2. To eliminate or decrease the number of normal microbiota, pathogens with samples collected from nonsterile sites are typically plated on ________ media.

ANS: selective DIF: Easy REF: 25.2 OBJ: 25.2c List procedures used to collect specimens from body sites containing normal microbiota.

MSC: Understanding 3. API 20E test strips contain wells with media that test for specific ________ reactions.

ANS: biochemical DIF: Easy REF: 25.3 OBJ: 25.3a Explain how biochemical profiles can be used to identify microbial pathogens.

MSC: Remembering 4. Growth of a bacterium in the presence of bile salts indicates the organism is ________.

ANS: Gram negative DIF: Moderate REF: 25.3 OBJ: 25.3b Discuss the major biochemical features that broadly differentiate Gram-negative and Gram-positive pathogens.

MSC: Applying 5. Mycobacterium tuberculosis is best identified by using a staining technique called a(n) ________ stain.

ANS: acid-fast; acid fast DIF: Easy REF: 25.3 OBJ: 25.3e Discuss differences between the acid-fast stain and Gram stain.

MSC: Remembering 6. The figure shown below illustrates antigen-capture ELISA. The structure labeled B in this figure

is a(n) ________.

ANS: antigen DIF: Moderate REF: 25.5 OBJ: 25.5a Describe how enzyme-linked immunosorbent assays can identify microbial antigens present in clinical samples or antimicrobial antibodies present in serum.

MSC: Understanding 7. A point-of-care (POC) assay that fails to identify 50% of individuals with a disease has low ________.

ANS: sensitivity DIF: Moderate REF: 25.6 OBJ: 25.6a Differentiate between assay specificity and sensitivity.

MSC: Understanding 8. Applying fluorescently tagged antibody stain to pleural fluid from a patient with Legionnaires’ disease and viewing the stained tissue using a fluorescence microscope is an example of ________ microscopy.

ANS: direct immunofluorescence DIF: Moderate REF: 25.5 OBJ: 25.5b Discuss the fluorescent antibody staining technique.

MSC: Remembering 9. This figure below shows a “red colloidal gold” test used to test for the presence of Streptococcus pneumoniae. This typical point-of-care laboratory test is known as a(n) ________ assay.

ANS: immunochromatographic DIF: Easy REF: 25.6 OBJ: 25.6a Differentiate between assay specificity and sensitivity.

MSC: Remembering SHORT ANSWER 1. A young child with meningitis is given an antibiotic prior to the identification of the causative pathogen. What is the appropriate term for this approach, and when would this approach most likely be used?

ANS: The approach of treating an infection prior to knowledge of the causative agent is referred to as empirical therapy. This approach is used frequently during life-threatening emergencies and is based on a physician’s best-educated guess regarding the pathogen.

DIF: Moderate REF: 25.1 OBJ: 25.1a List the reasons for identifying the cause of an infectious disease.

MSC: Applying 2. Ten patients are diagnosed with shigellosis. Explain the importance of having a clinical laboratory identify the strains of Shigella in each patient.

ANS: If multiple patients are infected with the same strain of Shigella, public health officials will use information from patients to try to determine the source of the outbreak and to stop the infection from spreading. If there are multiple strains present, there are multiple sources that must be investigated to stop the spread of these infections.

DIF: Difficult REF: 25.1 OBJ: 25.1b Explain the basic epidemiologic purpose of identifying the cause of an infectious disease.

MSC: Applying 3. A patient suspected of having septicemia is having blood samples drawn from both of her arms. Why is it important to draw blood samples from two different sites?

ANS:

Contamination of blood samples by skin microbiota is one problem that occurs with blood sampling. If blood is taken from two body sites and contains the same organism in both cultures, the organism is most likely the causative agent and not a contaminant. If the organism is found in a culture from one site but not the other, the organism is most likely present in the blood sample from contamination.

DIF: Moderate REF: 25.2 OBJ: 25.2b List procedures and precautions used to collect specimens from sterile body sites.

MSC: Analyzing 4. Describe the group of bacteria classified by Lancefield classification and explain the differences that define the classifications.

ANS: Lancefield classifications are used to distinguish beta-hemolytic streptococci. The Lancefield groups A–U are based on differences in the cell wall carbohydrate antigens of these streptococci.

DIF: Moderate REF: 25.3 OBJ: 25.3c Describe the Lancefield classification and its importance to clinical microbiology.

MSC: Understanding 5. Mannitol salt agar (MSA) contains a high concentration of salt that restricts the growth of most bacterial species. MSA also changes from pink to yellow when mannitol is fermented by some organisms. Describe the characteristics that make MSA both selective and differential.

ANS: The selective feature in mannitol salt agar is the salt that restricts the growth of certain organisms while allowing the growth of other organisms. MSA is also a differential medium because it includes substances that visually indicate a biochemical reaction, in this case mannitol fermentation, used to differentiate groups of organisms.

DIF: Moderate REF: 25.3 OBJ: 25.3d Explain the difference between selective and differential media and their use in clinical microbiology.

MSC: Evaluating 6. Why is polymerase chain reaction (PCR) required to detect nucleic acids in many clinical samples?

ANS: Clinical samples typically contain such low levels of nucleic acids that they are undetectable without amplification by PCR. PCR amplification can theoretically make billions of copies of DNA from a single strand of DNA. DIF: Moderate REF: 25.4 OBJ: 25.4a Discuss how the polymerase chain reaction can be used to identify pathogens in a clinical sample and the role of real-time PCR in clinical diagnosis.

MSC: Understanding 7. List two advantages of using real-time quantitative RT-PCR (qPCR) over tissue culture techniques when monitoring a patient with West Nile virus.

ANS: Real-time quantitative RT-PCR (qPCR) provides an estimate of the number of virus particles present.

Identifying the virus takes less time when qPCR is used.

DIF: Moderate

REF: 25.4

OBJ: 25.4b List the advantages and disadvantages of PCR, restriction fragment length polymorphisms, and biochemical strategies of pathogen identification.

MSC: Applying 8. A patient with a suspected Clostridium difficile infection is tested using a point-of-care (POC) rapid diagnostic test. List two disadvantages of using a POC rapid test to identify this disease.

ANS: The sensitivity of using a point-of-care test to identify Clostridium difficile toxin is much lower than the sensitivity of cultures or PCR. In this case, a POC test will be negative for 20–51% of patients infected with Clostridium difficile. Other disadvantages include the following: a lack of information regarding the antibiotic sensitivity of the pathogen, an increased risk of infection for the laboratory technician, and a likelihood of missing other pathogens that would be detected in a culture.

DIF: Difficult REF: 25.6 OBJ: 25.6c Discuss the advantages and disadvantages of point-of-care diagnostics.

MSC: Analyzing 9. CASE HISTORY A 55-year-old man complaining of headache, high fever, and neck stiffness was admitted to a local hospital. The man appeared confused and disoriented. He also complained of muscle weakness.

History indicated that he had received several mosquito bites approximately two weeks earlier. CSF and blood specimens were sent to the laboratory. The report the next day indicated no bacterial infection, but real-time PCR tests for various possible viral causes revealed that the patient was suffering from West Nile virus.

This patient is almost certainly pleased that his medical team made use of real-time PCR in the diagnostic process; however, PCR is not an automatic diagnostic for all potential causes of disease.

Discuss why PCR cannot be used as the exclusive diagnostic method for patients presenting with symptoms similar to this patient’s.

ANS: PCR requires specific primers for each organism tested, so it will require an essentially separate test for each potential pathogen (which must be decided in advance and have an established genome and assay developed). This can be costly and time-consuming, and it would fail to detect any pathogen not specifically targeted by the PCR. DIF: Moderate REF: Case History 25.5 OBJ: 25.4b List the advantages and disadvantages of PCR, restriction fragment length polymorphisms, and biochemical strategies of pathogen identification.

MSC: Analyzing 10. CASE HISTORY

Cindy, a 38-year-old woman with no significant previous medical history, came to the emergency department complaining of a mild sore throat persisting for three days. Her symptoms included arthralgia (joint pain), myalgia (muscle pain), and low-grade fever. The day before, she had a severe headache with neck stiffness, nausea, and vomiting. She was not taking medications, had no known drug allergies, and did not smoke. Cindy lived with her husband and two children, all of whom were well. Cerebrospinal fluid (CSF) was collected from a spinal tap and sent to the diagnostic laboratory.

The CSF appeared cloudy (it should be clear) and contained 871 white blood cells (mainly neutrophils) per microliter (normal is 0–10/l); the glucose level was 1 mg/dl (normal is 50–80 mg/dl); and the total protein level was 417 mg/dl (normal is under 45 mg/dl). Gram stain of a CSF smear revealed Gram-negative rods. The sample was streaked onto chocolate, blood, and Hektoen agars for microbial identification.

Why was the sample taken from Cindy streaked onto three separate agar plates? Describe the use of selective and differential media in the identification of pathogens—how might the growth on three media differ, and how will that alter the next steps in identifying a pathogen?

ANS: Some students may choose to discuss these three media specifically, but all answers should include a description that demonstrates awareness that selective media allows growth of only target organisms while differential media allows the clinician to distinguish some property of the bacterium in question.

These results are indicative of biochemical or other identifying differences that will inform the remainder of the identification process.

DIF: Moderate REF: Case History 25.3 OBJ: 25.3d Explain the difference between selective and differential media and their use in clinical microbiology.

MSC: Applying

Chapter 26: Epidemiology: Tracking Infectious Diseases LEARNING OBJECTIVES 26.1a Explain the four major links in a chain of infection.

26.1b Differentiate between descriptive and analytical epidemiology.

26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between disease prevalence and incidence.

26.1d Explain the three steps of surveillance and describe how molecular approaches can contribute to surveillance.

26.2a Discuss the nature of nosocomial infections and list the two most common forms.

26.2b List key questions that can help identify the source of a hospital-acquired infection.

26.2c Discuss procedures used to prevent hospital-acquired infections.

26.3a Discuss how global disease trends are recognized.

26.3b Explain the importance of finding the index case of an outbreak.

26.3c Employ online sources to track worldwide disease trends.

26.4a Describe the relationship between animal health and human disease.

26.4b Explain how molecular techniques can identify previously unrecognized and unculturable pathogens.

26.4c Discuss how technology contributes to the evolution of emerging pathogens and the spread of infectious disease.

26.4d Correlate the rise in reemerging diseases to the AIDS pandemic.

26.4e Explain how ecology and climate change influence the spread of infectious diseases.

26.5a Define the term “select agent.”

26.5b List some potential bioweapons.

26.5c Discuss the properties of an effective bioweapon.

MULTIPLE CHOICE 1. Charlotte touches a doorknob after an individual with MRSA touched the doorknob. Immediately after touching the knob, Charlotte scratches her leg and transmits some MRSA cells into a small wound.

The doorknob is functioning as a(n) a. etiologic agent. c. mode of transmission. b. reservoir. d. host.

ANS: C DIF: Easy REF: 26.1 OBJ: 26.1a Explain the four major links in a chain of infection.

MSC: Applying 2. A man infected with a viral respiratory infection sneezes and releases tiny droplets containing viral particles. Two minutes later, a woman breathes in some of these tiny droplets and becomes infected by the same viral infection. The movement of this virus from one individual to another is best described as the a. etiologic agent. c. mode of transmission. b. reservoir. d. host.

ANS: C DIF: Easy REF: 26.1 OBJ: 26.1a Explain the four major links in a chain of infection.

MSC: Understanding

3. Psittacosis is a zoonotic disease contracted by humans during contact with bacteria found in bird droppings. Human-to-human transmission is rare. Reducing contact with bird droppings will break the chain of infection by a. reducing the virulence of the bacteria responsible for causing the disease. b. affecting the bacteria’s portal of entry into the human body. c. reducing the number of organisms acting as reservoirs for the bacteria. d. reducing the transmission of bacteria from the reservoir to humans.

ANS: D DIF: Moderate REF: 26.1 OBJ: 26.1a Explain the four major links in a chain of infection.

MSC: Applying 4. Which of the following does NOT involve testing a hypothesis? a. descriptive epidemiology c. experimental study b. analytical epidemiology d. cohort study ANS: A DIF: Easy REF: 26.1 OBJ: 26.1b Differentiate between descriptive and analytical epidemiology.

MSC: Understanding 5. An investigator is collecting data identifying the time of year and locations of measles outbreaks within the United States over a ten-year period from 2000 to 2010. This investigator is most likely involved in a. descriptive epidemiology. c. analytical epidemiology. b. cohort studies. d. experimental studies.

ANS: A DIF: Easy REF: 26.1 OBJ: 26.1b Differentiate between descriptive and analytical epidemiology.

MSC: Understanding 6. Although sporadic outbreaks of measles occur in the United States, the disease is considered nonendemic. What differentiates measles from endemic diseases, such as chickenpox? a. Endemic diseases exhibit higher numbers of cases than a sporadic outbreak. b. Diseases that are not endemic lack a reservoir in the area. c. Endemic diseases do not exhibit sporadic outbreaks. d. Diseases that are not endemic remain in reservoirs without infecting humans.

ANS: B DIF: Easy REF: 26.1 OBJ: 26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between disease prevalence and incidence.

MSC: Understanding 7. The map below shows the incidence of syphilis in the United States in 2012. Based on the map, which of the following statements is true?

a. Efforts to prevent syphilis in the southern states failed to prevent an increase in the number of new cases in 2012. b. No individuals in Montana were infected with syphilis in 2012. c. The number of new cases of syphilis was higher in Texas than it was in North Dakota in 2012. d. The total number of active cases of syphilis in 2012 was highest in the southern states.

ANS: C DIF: Difficult REF: 26.1 OBJ: 26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between disease prevalence and incidence.

MSC: Evaluating 8. The map below shows the incidence of Lyme disease in the United States in 2012. Based on the map, which of the following statements is true?

a. Lyme disease exhibits geographical clusters in the Northeast. b. A decrease in Lyme disease vaccinations led to an increase in Lyme disease incidence in 2012. c. Lyme disease is maintained in a reservoir that is restricted to the Northeast. d. The number of Lyme disease cases has been steadily increasing since the 1970s.

ANS: A DIF: Moderate REF: 26.1 OBJ: 26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between disease prevalence and incidence.

MSC: Applying 9. Which of the following statements is a description of the prevalence of chlamydia? a. There are 57 active cases of chlamydia on a university campus. b. There were 57 new cases of chlamydia on a university campus last week. c. There were 123 new cases of chlamydia on a university campus last year. d. Young women on a university campus are twice as likely as young men to develop chlamydia.

ANS: A DIF: Moderate REF: 26.1 OBJ: 26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between disease prevalence and incidence.

MSC: Applying 10. Which of the following would indicate that efforts to control a disease are working? a. The disease becomes endemic. b. The disease prevalence increases. c. The disease incidence decreases. d. Outbreaks of the disease only occur every other year.

ANS: C DIF: Easy REF: 26.1 OBJ: 26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between disease prevalence and incidence.

MSC: Understanding 11. In the figure shown below, the lower part of the line on the graph represents a low, steady number of disease cases, which is indicative of a(n)

a. epidemic. b. pandemic.

c. outbreak. d. endemic disease.

ANS: D DIF: Easy REF: 26.1 OBJ: 26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between disease prevalence and incidence.

MSC: Applying 12. Which of the following is a factor that could explain the pattern of pertussis incidence shown below?

a. b. c. d.

There was an increased rate of vaccination beginning in 2002.

There was an improved laboratory detection of pertussis.

A more effective vaccine was introduced in 2012.

Fewer infants were vaccinated between 1982 and 1987.

ANS: B DIF: Difficult REF: 26.1 OBJ: 26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between

disease prevalence and incidence.

MSC: Analyzing

13. Which of the following statements describes one of the three steps of surveillance used for infectious diseases? a. Patients with infectious diseases are required to be seen by a physician at the CDC. b. Physicians are required to submit all patient records electronically to the CDC for review. c. Patient charts are reviewed by an infection control practitioner when an infectious disease is suspected. d. Incidence data is collected in all cases of bacterial infections within the United States.

ANS: C DIF: Easy REF: 26.1 OBJ: 26.1d Explain the three steps of surveillance and describe how molecular approaches can contribute to surveillance.

MSC: Understanding 14. Which of the following lists correctly identifies nosocomial infections from most common to least common? a. urinary tract, pneumonia, septicemia b. pneumonia, urinary tract, surgical wounds c. septicemia, surgical wounds, diarrhea d. diarrhea, urinary tract, pneumonia ANS: A DIF: Easy REF: 26.2 OBJ: 26.2a Discuss the nature of nosocomial infections and list the two most common forms.

MSC: Understanding 15. Mary, an elderly woman with an indwelling catheter, is admitted to a local hospital for treatment of pneumonia. Three days after her admission, Mary’s husband receives a call from the hospital. He is informed that Mary has a nosocomial infection. Which of the following statements is true? a. The nosocomial infection referred to is pneumonia. b. Mary has most likely developed a urinary tract infection. c. Of all hospital patients, 25–30% develop nosocomial infections. d. Mary’s nosocomial infection could have been prevented with improved ventilation.

ANS: B DIF: Difficult REF: 26.2 OBJ: 26.2a Discuss the nature of nosocomial infections and list the two most common forms.

MSC: Analyzing 16. Six patients with indwelling catheters develop urinary tract infections caused by Escherichia coli. The isolates from all six patients are identical. Which of the following steps should be used to identify the source of infection? a. Test for antibiotic resistance in the Escherichia coli isolated from each patient. b. Ensure that all health care providers wear gloves during care of infected patients. c. Begin using air filters in the rooms of all infected patients. d. Question hospital staff to determine whether infection control measures are being maintained.

ANS: D DIF: Difficult REF: 26.2 OBJ: 26.2b List key questions that can help identify the source of a hospital-acquired infection.

MSC: Applying 17. A nurse working in a large hospital harbors MRSA as part of the normal microbiota in his nose. He is most likely the source of a MRSA outbreak if a. all of the infected patients had been cared for by this nurse and the isolates are identical. b. the patients are all elderly and the isolates of MRSA are not genetically identical. c. all of the infected patients were seen by the same physician and half of the patients were

cared for by this nurse. d. all of the infected patients are on the same floor of the hospital and all have a history of heart problems.

ANS: A DIF: Moderate REF: 26.2 OBJ: 26.2b List key questions that can help identify the source of a hospital-acquired infection.

MSC: Analyzing 18. Which of the following is NOT an example of aseptic technique? a. use of antiseptic on skin prior to insertion of an IV line b. use of latex gloves during the insertion of an indwelling catheter c. disinfection of doorknobs and other inert surfaces d. use of trash can liners in all patient rooms ANS: D DIF: Easy REF: 26.2 OBJ: 26.2c Discuss procedures used to prevent hospital-acquired infections.

MSC: Applying 19. The figure shown below represents

a. b. c. d.

“daisy chain” movement of an infectious organism. an endemic organism colonizing a new area. a pandemic infection. syndromic surveillance of an index patient.

ANS: A DIF: Moderate REF: 26.2 OBJ: 26.2c Discuss procedures used to prevent hospital-acquired infections.

MSC: Applying 20. An individual case of diphtheria, a notifiable infectious disease, in a patient in Florida is confirmed by laboratory testing. This patient’s physician would be required to a. send a letter to the WHO in Geneva, Switzerland. b. contact the CDC in Atlanta, Georgia. c. treat the patient regardless of health insurance status. d. quarantine the patient for eight weeks.

ANS: B

DIF: Easy

REF: 26.3

OBJ: 26.3a Discuss how global disease trends are recognized.

MSC: Applying

21. Which of the following agencies would be the first to receive information about a reportable disease in the United States? a. the WHO c. a state health agency b. the CDC d. the FDA ANS: C DIF: Easy REF: 26.3 OBJ: 26.3a Discuss how global disease trends are recognized.

MSC: Applying

22. Fifteen individuals within one province in China are diagnosed with SARS. Epidemiologists will most likely a. quarantine the entire province immediately. b. contact the CDC in the United States to see if any cases were reported in the United States. c. wait to see if more cases of SARS are reported. d. try to identify the index case.

ANS: D DIF: Easy REF: 26.3 OBJ: 26.3b Explain the importance of finding the index case of an outbreak.

MSC: Understanding 23. The figure shown below indicates the spread of a highly infectious disease. The numbered circle, labeled “35,” indicates

a. the index case. b. a “super spreader.”

c. the beginning of a “daisy chain.” d. a noninfectious carrier.

ANS: B DIF: Moderate REF: 26.3 OBJ: 26.3b Explain the importance of finding the index case of an outbreak.

MSC: Understanding

24. The figure shown below indicates the spread of a highly infectious disease. The largest circle, labeled “1,” indicates

a. the index case. b. a “super spreader.”

c. the beginning of a “daisy chain.” d. an infectious carrier.

ANS: A DIF: Moderate REF: 26.3 OBJ: 26.3b Explain the importance of finding the index case of an outbreak.

MSC: Understanding 25. During the spring and summer of 2014 an online epidemiological search indicated an increase in U.S. searches for signs and symptoms associated with Ebola, a disease previously found in West Africa.

What was the most likely cause of this trend? a. Many individuals in the United States were infected with Ebola. b. Media reports of Ebola in other countries led to online searches in the United States. c. Individuals infected with Ebola fled to the United States. d. An Ebola epidemic occurred within the United States.

ANS: B DIF: Moderate REF: 26.3 OBJ: 26.3c Employ online sources to track worldwide disease trends.

MSC: Understanding 26. Vaccinating wild rodents or poultry a. has no effect on human health. b. reduces transmission of zoonotic diseases to humans. c. reduces the migration of microbes into temperate regions. d. increases the emergence of drug-resistant bacteria.

ANS: B DIF: Moderate REF: 26.4 OBJ: 26.4a Describe the relationship between animal health and human disease.

MSC: Understanding 27. Which of the following scenarios would help meet the goal of the One Health Initiative? a. vaccinating poultry against avian influenza to prevent influenza from being transmitted to humans b. taking steps to reduce carbon dioxide emissions to lessen the effects of climate change c. providing sanitation after flooding events to prevent gastrointestinal infections in humans d. increasing compliance during antibiotic treatment of tuberculosis patients to prevent emergence of drug-resistant strains of tuberculosis ANS: A

DIF: Difficult

REF: 26.4

OBJ: 26.4a Describe the relationship between animal health and human disease.

MSC: Analyzing 28. An infection with similar signs and symptoms appears in 24 prison inmates. There is evidence of bacterial etiology, but no laboratory has successfully isolated a bacterial agent in pure culture. Which of the following pieces of evidence would indicate a single bacterial species is causing the disease? a. DNA sequence analysis reveals an organism genetically similar to a known bacterium. b. the presence of eukaryotic DNA within biopsy tissues from all individuals c. high fevers and night sweats in all affected individuals d. 16S ribosomal RNA amplified in 50% of biopsy tissue samples ANS: A DIF: Difficult REF: 26.4 OBJ: 26.4b Explain how molecular techniques can identify previously unrecognized and unculturable pathogens.

MSC: Analyzing 29. Amplifying 16S ribosomal RNA from biopsy tissues would be useful in identifying the presence of a a. bacterium. c. multicellular parasite. b. specific virus. d. unicellular parasite.

ANS: A DIF: Difficult REF: 26.4 OBJ: 26.4b Explain how molecular techniques can identify previously unrecognized and unculturable pathogens.

MSC: Applying 30. If humans continue to develop rapid transportation systems into more parts of the world, we should expect to see a. pandemics tracing the path of the transportation systems. b. an increase in detection of blood-borne pathogens. c. a decrease in human encroachment into tropical rain forests. d. an increase in the spread of transmissible spongiform encephalopathies.

ANS: A DIF: Moderate REF: 26.4 OBJ: 26.4c Discuss how technology contributes to the evolution of emerging pathogens and the spread of infectious disease.

MSC: Applying 31. The figure below shows the pattern of short-range and long-range transportation connections. Which of the following accurately describes the connection between these patterns and infectious diseases?

a. Areas with more connections tend to experience fewer disease outbreaks because people are exposed to more microbes. b. Blood-borne pathogens tend to follow transportation routes, but respiratory infections do not. c. The rapid introduction of pathogens from one area to another strongly correlates with

modern travel routes. d. Patterns of modern transportation routes strongly correlate with social inequality and host susceptibility.

ANS: C DIF: Difficult REF: 26.4 OBJ: 26.4c Discuss how technology contributes to the evolution of emerging pathogens and the spread of infectious disease.

MSC: Evaluating 32. The figure below shows locations of severe acute respiratory syndrome (SARS) outbreaks. Which of the following is the best explanation for the pattern of outbreaks?

a. A new coronavirus appeared simultaneously in each of the locations when spontaneous mutations occurred. b. An index case patient spread a virus to other individuals who traveled rapidly around the globe. c. A previously undiagnosed virus was reported as SARS in all locations simultaneously. d. Climate change allowed mosquitoes carrying a virus to move into all of the locations.

ANS: B DIF: Moderate REF: 26.4 OBJ: 26.4c Discuss how technology contributes to the evolution of emerging pathogens and the spread of infectious disease.

MSC: Evaluating 33. In developed countries, healthy individuals are typically able to handle occasional infections with some disease agents, but immunocompromised individuals are affected by these agents. Examples of agents that can cause disease in immunocompromised individuals but that are often repelled by healthy individuals are a. parasites such as ascariasis. b. viruses such as hantavirus. c. bacteria such as Streptococcus pyogenes. d. antibiotic-resistant bacteria such as MRSA. ANS: A DIF: Moderate REF: 26.4 OBJ: 26.4d Correlate the rise in reemerging diseases to the AIDS pandemic.

MSC: Analyzing 34. The AIDS pandemic has influenced reemerging diseases by a. increasing the number of immunocompromised individuals who are susceptible to diseases that were previously declining in developed countries.

b. leading to an increase in the number of disease vectors throughout the world. c. increasing the prevalence of protozoal and parasitic infections that were declining in underdeveloped countries. d. causing evolution to occur in diseases that were close to being eradicated in all countries.

ANS: A DIF: Moderate REF: 26.4 OBJ: 26.4d Correlate the rise in reemerging diseases to the AIDS pandemic.

MSC: Analyzing 35. Which of the following is likely to occur as a result of climate change? a. Insect vectors will migrate from tropical regions to once-temperate regions. b. Gastrointestinal infections will decrease in tropical regions. c. Microbes currently found in temperate regions will move to tropical regions. d. Extreme weather will decrease and diseases will become less seasonal.

ANS: A DIF: Moderate REF: 26.4 OBJ: 26.4e Explain how ecology and climate change influence the spread of infectious diseases.

MSC: Applying 36. This figure below shows locations where cases of Dengue fever are increasing. Dengue fever is caused by a virus transmitted by Aedes genus mosquitoes. Warmer temperatures and increased precipitation both influence populations of Aedes mosquitoes. Which of the following statements represents the best prediction for future outbreaks of Dengue fever?

a. Aedes mosquitoes and Dengue fever will become extinct as both temperature and precipitation decrease in tropical regions. b. Dengue fever outbreaks will remain restricted to a few locations because mosquitoes are unable to expand their range. c. Humans will become immune to Dengue fever as more individuals are exposed to the virus. d. Climate change will lead to Dengue fever outbreaks in once-temperate areas north and south of the sites of current outbreaks.

ANS: D DIF: Difficult REF: 26.4 OBJ: 26.4e Explain how ecology and climate change influence the spread of infectious diseases.

MSC: Analyzing 37. A select agent

a. b. c. d.

is chosen by a bio-warfare committee to decimate a population. is a highly contagious, infectious agent with a high mortality rate. has been designed by humans to resemble biological molecules. is a new genetic strain of diseases eradicated in the wild.

ANS: B DIF: Moderate REF: 26.5 OBJ: 26.5a Define the term “select agent.”

MSC: Applying

38. Which of the following is NOT an example of a bioweapon? a. distributing anthrax spores in mailed letters b. giving susceptible individuals blankets used by smallpox patients c. failing to monitor animal health in towns where humans live in close contact with animals d. catapulting bodies of plague victims over castle walls ANS: C DIF: Easy REF: 26.5 OBJ: 26.5b List some potential bioweapons.

MSC: Applying

39. What features would allow a virus to be used effectively as a bioweapon? a. a high infectious dose c. person-to-person transmission b. transmission via an insect vector d. quick pathogen detection systems ANS: C DIF: Easy REF: 26.5 OBJ: 26.5c Discuss the properties of an effective bioweapon.

MSC: Understanding

40. Which of the following bioweapons would be used with the intent of terrorizing people rather than inflicting death on large numbers of individuals? a. a virus that is easily transmitted between people and to which most individuals in a population are susceptible b. a virus with a low infectious dose and high mortality that is easily dispersed through the air c. a virus that is not easily transmitted between people and has a high infectious dose d. a virus that is easily dispersed from one infected person to many within a day and has a high mortality rate ANS: C DIF: Moderate REF: 26.5 OBJ: 26.5c Discuss the properties of an effective bioweapon.

MSC: Analyzing

41. CASE HISTORY In 2003, a 48-year-old man was hospitalized in Dutchess County, New York, with a 38.4 C (101 F ) fever, headache, and body aches. He also had difficulty breathing. He had just returned from a business trip to China. Health care workers were stumped for a diagnosis. Serological tests, PCR analysis, and fluorescent antibody stains failed to reveal a cause. Was this something new?

The disease in the case history was determined to be a new agent, SARS. One week later a 27-year-old local patient with no history of travel presents with similar symptoms at a hospital in Florida. How should hospital personnel respond? a. Begin with serological tests, PCR, and antibody stains, as they did in the case of the original infection. b. Immediately offer the treatment for SARS. c. Utilize whole-genome sequencing to determine the nature of the pathogen. d. Prescribe a broad-spectrum antibiotic.

ANS: A DIF: Easy REF: Case History 26.2 OBJ: 26.4b Explain how molecular techniques can identify previously unrecognized and unculturable pathogens.

MSC: Analyzing

COMPLETION 1. The etiologic agent of a microbe, the agent’s reservoir, the mode of transmission, and its host make up what is known as the ________.

ANS: chain of infection DIF: Easy REF: 26.1 OBJ: 26.1a Explain the four major links in a chain of infection.

MSC: Remembering 2. An epidemiologist collects information about the person, place, and time of infection by the varicella zoster virus. After collecting this information, she forms a hypothesis about the possible risk factors involved and uses an observational study to test her hypothesis. This type of epidemiology is ________.

ANS: analytical; analytical epidemiology DIF: Easy REF: 26.1 OBJ: 26.1b Differentiate between descriptive and analytical epidemiology.

MSC: Remembering 3. A disease transmitted from animals to humans is called a ________ disease.

ANS: zoonotic DIF: Easy REF: 26.4 OBJ: 26.4a Describe the relationship between animal health and human disease.

MSC: Remembering 4. An infectious agent with a high mortality rate that is highly contagious and lacks a vaccine and effective treatment is known as a ________.

ANS: select agent DIF: Easy REF: 26.5 MSC: Remembering

OBJ: 26.5a Define the term “select agent.”

5. One potential bioweapon is a virus that has been eradicated from natural populations; only two WHOsanctioned laboratories still maintain vials of this virus. This virus is ________.

ANS: smallpox; variola major; variola major virus DIF: Easy REF: 26.5 MSC: Remembering

OBJ: 26.5b List some potential bioweapons.

SHORT ANSWER 1. Explain the relationship between the terms endemic, epidemic, and pandemic.

ANS:

Diseases that exhibit a low, steady number of cases in a given geographic location and are considered native to that area are referred to as endemic diseases. If the number of cases increases rapidly and expands geographically, the disease is referred to as epidemic. If the epidemic continues to grow and spreads across continents, the disease has reached a pandemic level.

DIF: Moderate REF: 26.1 OBJ: 26.1c Define “endemic,” “epidemic,” and “pandemic,” and explain the difference between disease prevalence and incidence.

MSC: Understanding 2. A young man infected with multidrug resistant (MDR) tuberculosis is attempting to immigrate into the United States. A mandatory chest X-ray does not show any lung tubercles that are indicative of tuberculosis, and an acid-fast stain also fails to detect his early infection. Describe an approach that is able to detect an early tuberculosis infection.

ANS: Molecular techniques like PCR amplification and other DNA-based strategies are much more sensitive. PCR amplification allows detection of fewer cells than staining techniques.

DIF: Moderate REF: 26.1 OBJ: 26.1d Explain the three steps of surveillance and describe how molecular approaches can contribute to surveillance.

MSC: Understanding 3. You turn on a television and catch the end of an interview with a young patient who developed a lifethreatening MRSA infection after a routine surgery to remove his appendix. What is the term for this type of surgical wound infection, and how common are these infections?

ANS: This patient developed a nosocomial or health care–associated infection (HAI). Nosocomial infections affect 5–10% of hospital patients. Surgical wound infections comprise 20–30% of nosocomial infections.

DIF: Easy REF: 26.2 OBJ: 26.2a Discuss the nature of nosocomial infections and list the two most common forms.

MSC: Understanding 4. An elderly man is admitted to a hospital after he experiences a heart attack. Four days after his admission he is diagnosed with pneumonia caused by Pseudomonas. Three other patients in the same hospital at the same time also develop pneumonia caused by Pseudomonas. List at least four key questions an infectious disease epidemiologist would want answered as the source of these infections is investigated.

ANS: The key questions are as follows: 1. Are the isolates in all patients the same?; 2. Has any single member of the hospital staff been in physical contact with all of the infected patients?; 3. Was there common contact with a medical instrument, medical supplies, food, or water?; 4. Has there been physical contact between affected patients?; 5. Is the infectious agent airborne? If so, are there air ducts linking the affected rooms?; 6. Have surfaces and hospital staff been tested for presence of the organism?; and 7. Have standard infection-control measures been maintained?

DIF: Moderate REF: 26.2 OBJ: 26.2b List key questions that can help identify the source of a hospital-acquired infection.

MSC: Remembering

5. A nurse stops by a new patient’s room and observes a sign outside the door indicating that a disposable mask and gown should be worn in addition to latex gloves when caring for this patient. What are the two broad categories of patients that would require this extra step, and who is this gear designed to protect in each category?

ANS: Patients who are immunocompromised and patients with dangerous infectious diseases require the extra protection of a gown and mask in addition to latex gloves. In the case of an immunocompromised patient, the extra protection is designed to protect the patient. In the case of patients with infectious diseases, the extra protection helps protect the health care worker and other visitors as well as other patients in the hospital.

DIF: Moderate REF: 26.2 OBJ: 26.2c Discuss procedures used to prevent hospital-acquired infections.

MSC: Applying 6. What type of disease is reported by syndromic surveillance, and how does this type of surveillance fit into tracking global outbreaks of disease?

ANS: New emerging diseases of unknown etiology are reported to central health agencies such as the CDC in the United States. An increase in reports of a new disease with common symptoms will allow epidemiologists to recognize an epidemic in progress. In response to reports, efforts will be made by epidemiologists to determine the source and cause of the outbreak.

DIF: Difficult REF: 26.3 OBJ: 26.3a Discuss how global disease trends are recognized.

MSC: Understanding

7. Why is it important to recognize “patient zero” during an epidemic of a disease such as severe acute respiratory syndrome (SARS)?

ANS: Identifying the index case, or patient zero, is important in containing the spread of an epidemic. Patient zero and any individuals who had contact with him or her should be treated or quarantined to prevent the spread of the disease.

DIF: Moderate REF: 26.3 OBJ: 26.3b Explain the importance of finding the index case of an outbreak.

MSC: Understanding 8. Anyone with a computer and Internet access can use Google Trends to investigate the search frequency for diseases such as influenza. What are two explanations for why online searches for an infectious disease will crudely track actual cases of the disease?

ANS: Symptomatic individuals may search online for an explanation of their illnesses. Media reports may also lead to individuals seeking information.

DIF: Moderate REF: 26.3 OBJ: 26.3c Employ online sources to track worldwide disease trends.

MSC: Applying

9. Koch’s postulates require that an organism suspected as the causative agent of a disease be grown in pure culture. In some cases scientists have not successfully cultured an organism but have used molecular techniques to identify the cause of a new disease. Describe the molecular techniques that may be used to identify a previously uncultured bacterium and indicate that the identified organism is the causative agent.

ANS: PCR amplification and DNA sequence analysis may be used to identify a suspected organism.

Identification of the causative agent requires the same organism be found in all instances of the disease.

DIF: Moderate REF: 26.4 OBJ: 26.4b Explain how molecular techniques can identify previously unrecognized and unculturable pathogens.

MSC: Understanding 10. Describe two ways in which technology has contributed to the emergence of pathogens and the spread of infectious diseases.

ANS: People have begun moving into habitats that have increased human contact with animals. This increased contact has increased the occurrence of zoonotic diseases. Humans have developed longrange jet connections that allow a rapid spread of diseases around the globe and increase the likelihood of pandemics. Other technologies that have spread pathogens are the use of blood banks, modern farming practices, and modern meat-processing plants.

DIF: Easy REF: 26.4 OBJ: 26.4c Discuss how technology contributes to the evolution of emerging pathogens and the spread of infectious disease.

MSC: Understanding 11. How has the AIDS pandemic influenced reemerging diseases in developed countries?

ANS: Many diseases that were under control in developed countries have reemerged. Immunocompromised individuals are more susceptible to infections that healthy individuals are able to fight off. AIDS patients are prone to parasitic infections as well as tuberculosis, even in developed countries where these diseases were previously controlled.

DIF: Easy REF: 26.4 OBJ: 26.4d Correlate the rise in reemerging diseases to the AIDS pandemic.

MSC: Understanding 12. Describe two ways in which climate change can influence when and where diseases occur.

ANS: Climate change leads to more severe weather events, such as flooding. An increase in gastrointestinal infections occurs after flooding due to decreased sanitation. Climate change also impacts the distribution of animals and the microbes they carry. As animals and their microbes move into new habitats, diseases that were previously found in tropical regions are moving into regions that are more temperate.

DIF: Difficult REF: 26.4 OBJ: 26.4e Explain how ecology and climate change influence the spread of infectious diseases.

MSC: Applying

13. List the characteristics that would make a bioweapon effective in terms of bio-warfare or inflicting as many casualties as possible.

ANS: In terms of inflicting death, a bioweapon would need to have a low infectious dose, be transmitted easily from one person to another, and be able to infect a large percentage of the population.

DIF: Easy REF: 26.5 OBJ: 26.5c Discuss the properties of an effective bioweapon.

MSC: Remembering

14. CASE HISTORY Stephanie was a bright seven-year-old girl who came to her rural Manitoba hospital for a tonsillectomy. She was a little scared, but her mother was with her and she liked the surgeon, Dr. Ryan, and his funny Winnie-the-Pooh ties. Sometimes she would even grab his tie while Dr. Ryan was examining her. However, she did not much like the IV catheter Dr. Ryan had to insert in her arm.

It hurt a little, but she was brave and did not cry much. The surgery went well and Stephanie was recovering in her hospital room a few hours later. However, that night the nurse noted her temperature had risen to 102 F. By the next day, Stephanie’s heart was racing and her breathing was labored. She was rushed to the pediatric intensive care unit and empiric antibiotic therapy was initiated. Despite this treatment, her blood pressure began to fall. Stephanie was diagnosed with postsurgical septic shock. To everyone’s horror, Stephanie died two days later of MRSA sepsis. The organism recovered from her blood was a MRSA strain identical to one causing a wound infection in a 57-year-old man two floors down.

Discuss at least three key measures implemented in health care settings that are designed to prevent transmission of infectious diseases in health care environments, and offer a scenario that reveals how a breach in these procedures could have led to Stephanie’s tragic death.

ANS: Though the inadequate use of gowns is used as an explanation in the text, many others are equally plausible. Hand sanitation, gowning, and aseptic technique, as well as other reasonable answers, may be offered. The theory of the failure in procedures should match both the protective measure and the pathogen—that is, not related to an aerosol but rather a contact-transmitted disease agent.

DIF: Moderate REF: Case History 26.1 OBJ: 26.2c Discuss procedures used to prevent hospital-acquired infections.

MSC: Evaluating 15. CASE HISTORY Stephanie was a bright seven-year-old girl who came to her rural Manitoba hospital for a tonsillectomy. She was a little scared, but her mother was with her and she liked the surgeon, Dr. Ryan, and his funny Winnie-the-Pooh ties. Sometimes she would even grab his tie while Dr. Ryan was examining her. However, she did not much like the IV catheter Dr. Ryan had to insert in her arm. It hurt a little, but she was brave and did not cry much. The surgery went well and Stephanie was recovering in her hospital room a few hours later. However, that night the nurse noted her temperature had risen to 102 F. By the next day, Stephanie’s heart was racing and her breathing was labored. She was rushed to the pediatric intensive care unit and empiric antibiotic therapy was initiated. Despite this treatment, her blood pressure began to fall. Stephanie was diagnosed with postsurgical septic shock. To everyone’s horror, Stephanie died two days later of MRSA sepsis. The organism recovered from her blood was a MRSA strain identical to one causing a wound infection in a 57-year-old man two floors down.

Explain the process by which hospital staff may have been able to identify Stephanie’s infection as nosocomial and identify the same isolate from other patients.

ANS: An awareness of HAIs and constant vigilance by hospital epidemiologists is required. Though MRSA is now recognized as a common nosocomial infection, it is still investigated using the principal questions in Chapter 26—for example, “Is each patient infected with an identical isolate?”

DIF: Moderate REF: Case History 26.1 OBJ: 26.2b List key questions that can help identify the source of a hospital-acquired infection.

MSC: Evaluating

Chapter 27: Environmental and Food Microbiology LEARNING OBJECTIVES 27.1a Describe the various roles of microbes in natural ecosystems and the kinds of ecosystem services that microbes provide.

27.1b Explain how physical factors determine which microbes grow in a given habitat.

27.1c Outline how microbes participate in the food chains of ocean, soil, and wetland.

27.1d Explain the phenomenon of biochemical oxygen demand and the cause of dead zones.

27.2a Explain the different kinds of microbe-animal symbioses, including mutualism, synergism, commensalism, amensalism, and parasitism.

27.2b Describe the digestive communities of animals.

27.2c Explain how microbial communities contribute to human health.

27.3a Describe the roles of bacteria and fungi in the production of cheese and fermented soy foods.

27.3b Outline the process of ethanolic fermentation in the production of beer and wine.

27.3c Explain why fermented foods and beverages retain high food value.

27.4a Explain the difference between food spoilage and food contamination.

27.4b Outline the different processes of spoilage of dairy products, meat, seafood, and plant foods. Explain why different types of food spoil differently.

27.4c Describe the various physical and chemical approaches to food preservation.

27.5a Describe the processes of the water cycle, and explain how human and industrial wastewater enter it.

27.5b Explain the stages of standard wastewater treatment, including the key participation of microbial ecosystems.

27.6a Describe how microbes participate in the global cycling of carbon by converting carbon between its reduced and oxidized forms.

27.6b Explain the implications of global carbon cycling for human health.

27.6c Outline the unique roles of microbes in cycling different forms of nitrogen.

27.6d Explain how human technology perturbs the global nitrogen cycle.

MULTIPLE CHOICE 1. If bacteria and archaea are removed from an ecosystem, which of the following environmental services would be absent? a. nitrogen fixation b. capture of energy from sunlight c. decomposition of dead matter d. dissimilation of biomass by respiration ANS: A DIF: Moderate REF: 27.1 OBJ: 27.1a Describe the various roles of microbes in natural ecosystems and the kinds of ecosystem services that microbes provide.

MSC: Analyzing 2. The figure below shows a food web. Which of the following statements is true?

a. Ten percent of the carbon dioxide fixed by grazers is used by decomposers. b. Ten percent of the carbon dioxide fixed by primary producers is used by predators. c. Ninety-nine percent of the carbon dioxide fixed by primary producers is lost by the second trophic level. d. Grazers consume ten percent of the decomposers.

ANS: C DIF: Moderate REF: 27.1 OBJ: 27.1a Describe the various roles of microbes in natural ecosystems and the kinds of ecosystem services that microbes provide.

MSC: Analyzing 3. A microbe’s contribution to an ecosystem’s health depends on the a. microbe’s genome and the physical and chemical characteristics of the environment. b. microbe’s age and number of primary producers in the environment. c. microbe’s ability to cycle carbon and the number of decomposers in the ecosystem. d. bioremediation capacity of the microbe and the number of predators in the ecosystem.

ANS: A DIF: Difficult REF: 27.1 OBJ: 27.1a Describe the various roles of microbes in natural ecosystems and the kinds of ecosystem services that microbes provide.

MSC: Applying 4. Which of the following statements describes the relationship between physical factors and the ability of microbes to grow? a. Most microbes survive best at normal human body temperature. b. Different microbial species are able to survive different physical conditions. c. All microbes require oxygen for growth. d. Microbial growth is not influenced by physical factors.

ANS: B DIF: Moderate REF: 27.1 OBJ: 27.1a Describe the various roles of microbes in natural ecosystems and the kinds of ecosystem services that microbes provide.

MSC: Applying 5. High salt concentrations limit the growth of microbes adapted to freshwater conditions because a. salt prevents microbes from using oxygen as an electron acceptor during aerobic cellular respiration. b. high salt concentrations increase the temperature of the environment above the range at which most microbes can survive. c. freshwater is a hypotonic solution and microbes living in freshwater do not have a need for mechanisms to reduce water loss. d. a high salt concentration leads to a sharp decline in the pH of the environment.

ANS: C

DIF: Difficult

REF: 27.1

OBJ: 27.1b Explain how physical factors determine which microbes grow in a given habitat.

MSC: Evaluating 6. Which of the following relationships is shown in the soil food web below?

a. b. c. d.

Vertebrate animals are consumed by birds.

Some nematodes consume fungi and bacteria.

Fungi utilize carbon dioxide produced by plants.

Bacteria consume protozoa.

ANS: B DIF: Easy REF: 27.1 OBJ: 27.1c Outline how microbes participate in the food chains of ocean, soil, and wetland.

MSC: Applying 7. The figure shown below indicates a dead zone within the Gulf of Mexico. In the area labeled “Lower Mississippi,” a(n) ________ would be expected.

a. increase in the number of fish and invertebrates b. decrease in algal growth within the Mississippi River and tributaries c. increase in photosynthetic bacteria

d. increase in nitrates from agricultural fertilizers ANS: D DIF: Easy REF: 27.1 OBJ: 27.1d Explain the phenomenon of biochemical oxygen demand and the cause of dead zones.

MSC: Applying 8. A high school student visiting Lake Erie reads a sign indicating that it is unsafe to swim at a beach because of a toxin called microcystin. The student does some research and finds the following relationship between fertilizer, algae, heterotrophic bacteria, and fish: fertilizer runoff causes a. algal blooms, which lead to an increase in heterotrophic bacteria and a decrease in fish. b. increases in heterotrophic bacteria, which leads to an increase in algal blooms and a decrease in fish. c. increases in fish populations, which leads to decreases in heterotrophic bacteria and algae populations. d. algal blooms, which lead to a decrease in heterotrophic bacteria and an increase in fish.

ANS: A DIF: Moderate REF: 27.1 OBJ: 27.1d Explain the phenomenon of biochemical oxygen demand and the cause of dead zones.

MSC: Understanding 9. Which of the following statements correctly describes the relationship between biochemical oxygen demand (BOD), heterotrophic bacteria, and fish? a. The presence of fish increases the number of heterotrophic bacteria in an area, which decreases the BOD. b. Increases in the number of heterotrophic bacteria decrease the BOD, which decreases the number of fish. c. The BOD of a marine environment is independent of populations of heterotrophic bacteria and fish. d. Heterotrophic bacteria generate oxygen, which increases the BOD and increases the number of fish.

ANS: B DIF: Difficult REF: 27.1 OBJ: 27.1d Explain the phenomenon of biochemical oxygen demand and the cause of dead zones.

MSC: Analyzing 10. An obligate association exists between a gut microbe and an insect. A new mutation in the microbe allows the microbe to utilize nutrients that were previously accessible to the insect. This change benefits the microbe but causes some harm to the insect. The change in the relationship is best described as a change from a. mutualism to parasitism. c. commensalism to amensalism. b. synergism to parasitism. d. parasitism to synergism.

ANS: A DIF: Difficult REF: 27.2 OBJ: 27.2a Explain the different kinds of microbe-animal symbioses, including mutualism, synergism, commensalism, amensalism, and parasitism.

MSC: Applying 11. A new species of human gut bacteria is discovered. Scientists find that during the process of breaking down and utilizing undigested plant fibers, the bacteria also produces a vitamin that is absorbed by humans. The relationship described is an example of a. amensalism. c. commensalism. b. parasitism. d. mutualism.

ANS: D DIF: Easy REF: 27.2 OBJ: 27.2a Explain the different kinds of microbe-animal symbioses, including mutualism, synergism, commensalism, amensalism, and parasitism.

MSC: Applying

12. The largest population of fermenters is found in the chamber labeled

a. A. b. B.

c. C. d. D.

ANS: B DIF: Moderate REF: 27.2 OBJ: 27.2b Describe the digestive communities of animals.

MSC: Understanding

13. Shifting a cow’s diet results in a(n) a. change in the pathway of digestion through the cow’s four stomach chambers. b. change in the microbial populations present within the cow’s gut. c. increase in antibiotic-resistant bacteria found in the environment. d. decrease in the amount of water and short-chain acids absorbed in the omasum.

ANS: B DIF: Moderate REF: 27.2 OBJ: 27.2b Describe the digestive communities of animals.

MSC: Applying

14. Bacteriocins are molecules that are produced by a. some bacteria and prevent pathogens from adhering to the gut lining. b. methanogens and cause flatulence in cows. c. digestive microbes in termites and allow digestion of cellulose. d. viruses and increase the virulence of zoonotic diseases.

ANS: A DIF: Difficult REF: 27.2 OBJ: 27.2c Explain how microbial communities contribute to human health.

MSC: Remembering 15. Which of the following illustrates a positive interaction between human microbiota and the immune system? a. downregulation of cytokines within the colon b. production of short-chain acids within the colon c. conversion of hydrogen gas and carbon dioxide into methane d. secretion of acids that decrease pH within the colon ANS: A DIF: Moderate REF: 27.2 OBJ: 27.2c Explain how microbial communities contribute to human health.

MSC: Applying 16. A commonality of bread, cheese, beer, and chocolate is the use of ________ in their production. a. anaerobic fermentation c. acetic acid bacteria b. lactic acid bacteria d. highly engineered microbial strains ANS: A DIF: Easy REF: 27.3 OBJ: 27.3a Describe the roles of bacteria and fungi in the production of cheese and fermented soy

foods.

MSC: Analyzing

17. During alcoholic fermentation of grains, hops plays a role in providing a. sugar for ethanol production. b. enzymes to break down starch. c. antibacterial properties to extend the shelf life of beer. d. the flavor of wines.

ANS: C DIF: Moderate REF: 27.3 OBJ: 27.3b Outline the process of ethanolic fermentation in the production of beer and wine.

MSC: Understanding 18. Although beer and wine are both produced through ethanolic fermentation, there are some differences in the pathway. Which of the following illustrates one of these differences? a. Wine production involves the breakdown of long-chain carbohydrates. b. Wine is produced from simple sugars. c. Only beer production involves pyruvate as an intermediate. d. Only wine production can lead to the production of diacetyl.

ANS: B DIF: Moderate REF: 27.3 OBJ: 27.3b Outline the process of ethanolic fermentation in the production of beer and wine.

MSC: Applying 19. Which of the following molecules is converted to ethanol in the production of beer? a. aldehydes c. maltose b. long-chain alcohols d. fatty acids ANS: C DIF: Easy REF: 27.3 OBJ: 27.3b Outline the process of ethanolic fermentation in the production of beer and wine.

MSC: Applying 20. As a result of using common bread mold to ferment soybeans during the production of tempeh, a. phytate is introduced. c. protein content is increased. b. lectins are decreased. d. autoimmune diseases are induced.

ANS: B DIF: Difficult REF: 27.3 OBJ: 27.3c Explain why fermented foods and beverages retain high food value.

MSC: Applying 21. Curds from milk fermentation are particularly valuable because they a. are a source of concentrated protein. b. contain more vitamins than milk. c. contain acetic acid that can be used to preserve other foods. d. have an indefinite shelf life and do not require refrigeration.

ANS: A DIF: Easy REF: 27.3 OBJ: 27.3c Explain why fermented foods and beverages retain high food value.

MSC: Understanding 22. One benefit of food fermentation is the generation of vitamin a. A. c. B12. b. C. d. D. ANS: C DIF: Easy REF: 27.3 OBJ: 27.3c Explain why fermented foods and beverages retain high food value.

MSC: Remembering

23. Chantel becomes seriously ill with diarrhea and vomiting after eating some potato salad. Upon questioning she states that there was no off odor and the potato salad tasted fine. Which of the following is the most likely explanation for her illness? a. Enzymatic processes that began occurring after the potatoes were harvested led to her illness. b. Oxidation by air converted some of the lipids in the potato salad into rancid products. c. Acidic fermentation by microbes affected the pH of the potato salad, which made her ill. d. A small number of pathogens caused food contamination.

ANS: D DIF: Difficult REF: 27.4 OBJ: 27.4a Explain the difference between food spoilage and food contamination.

MSC: Analyzing 24. Spoilage of food can alter the odor or taste of the food. Which of the following statements correctly matches a pathway to the spoilage that results? a. Acidic fermentation leads to a bitter flavor. b. Alkaline products from microbial metabolism lead to a sour flavor. c. Oxidation of fats leads to rancidity. d. Decomposition of proteins and amino acids leads to a salty flavor.

ANS: C DIF: Easy REF: 27.4 OBJ: 27.4a Explain the difference between food spoilage and food contamination.

MSC: Applying 25. A grocery store chain wants to respond to consumer demands to reduce the use of Styrofoam trays and plastic wrap used in vacuum-packed food packages. In which of the following foods will food quality be most affected by a reduction in the use of vacuum packages? a. ground beef c. cheese b. pork chops d. fresh herbs ANS: B DIF: Difficult REF: 27.4 OBJ: 27.4b Outline the different processes of spoilage of dairy products, meat, seafood, and plant foods. Explain why different types of food spoil differently.

MSC: Evaluating 26. The figure below shows restriction-digested DNA fragments from Salmonella enterica that have been separated by electrophoresis. The Salmonella enterica was isolated from individuals with illness and two jars of peanut butter. These fragments indicate

a. b. c. d.

food contamination in both jars of peanut butter. no relationship between the ill individuals and peanut butter. that individuals became ill after eating peanut butter from Jar 2. food contamination in Jar 1, but not in Jar 2.

ANS: A DIF: Difficult REF: 27.4 OBJ: 27.4b Outline the different processes of spoilage of dairy products, meat, seafood, and plant foods. Explain why different types of food spoil differently.

MSC: Analyzing

27. What is the most available carbon-based nutrient in milk that is used by microbes during anaerobic fermentation? a. lactose c. protein b. glucose d. fat ANS: A DIF: Moderate REF: 27.4 OBJ: 27.4b Outline the different processes of spoilage of dairy products, meat, seafood, and plant foods. Explain why different types of food spoil differently.

MSC: Understanding 28. Dehydrating and freezing both work well to preserve foods because they a. make water unavailable to microbes. c. kill microbes. b. both involve low temperatures. d. remove nutrients used by microbes.

ANS: A DIF: Difficult REF: 27.4 OBJ: 27.4c Describe the various physical and chemical approaches to food preservation.

MSC: Analyzing 29. According to the graph below of microbial growth in a food, which statement is true?

a. b. c. d.

More growth occurs at 4C. The rate of growth is lower at 6C. There were preexisting contaminants in both cases.

On day 10 the population at 4C was half of the population at 6C.

ANS: C DIF: Moderate REF: 27.4 OBJ: 27.4c Describe the various physical and chemical approaches to food preservation.

MSC: Evaluating 30. Historically, there has been concern about the ingestion of nitrite used as a food preservative. Why does nitrite work well as a food preservative? a. Nitrites are used to inhibit aerobic respiration of bacteria. b. Nitrites increase carbon dioxide levels. c. Nitrites have antimicrobial properties. d. Nitrites cross cell membranes and release protons intracellularly.

ANS: A DIF: Moderate REF: 27.4 OBJ: 27.4c Describe the various physical and chemical approaches to food preservation.

MSC: Understanding 31. Of the following physical means of preserving foods, the only method capable of destroying endospores is a. pasteurization. c. dehydration.

b. canning.

d. decreased oxygen.

ANS: B DIF: Moderate REF: 27.4 OBJ: 27.4c Describe the various physical and chemical approaches to food preservation.

MSC: Applying 32. Human sewage and industrial effluents are abundant in a. short-chain fatty acids and urea. b. monosaccharides and insoluble fiber. c. amino acids and urea. d. amino acids and insoluble fiber.

ANS: A DIF: Moderate REF: 27.5 OBJ: 27.5a Describe the processes of the water cycle, and explain how human and industrial wastewater enter it.

MSC: Understanding 33. When carbon- and nitrogen-rich wastes are released into aquatic environments a. algae populations decrease. c. invertebrate populations increase. b. fish populations increase. d. bacterial populations increase.

ANS: D DIF: Easy REF: 27.5 OBJ: 27.5a Describe the processes of the water cycle, and explain how human and industrial wastewater enter it.

MSC: Understanding 34. A wastewater treatment facility experiences a massive die-off of anaerobic bacteria. How will this dieoff affect the treatment process? a. Primary treatment will be affected. b. Tertiary treatment will be affected. c. Secondary treatment will be affected. d. Treatment will not be affected because the microbial ecosystem is normally aerobic.

ANS: C DIF: Moderate REF: 27.5 OBJ: 27.5b Explain the stages of standard wastewater treatment, including the key participation of microbial ecosystems.

MSC: Applying 35. Aeration basins at wastewater treatment facilities a. encourage fermentation. b. maximize microbial breakdown of pollutants to carbon dioxide and nitrates. c. limit free-floating populations of bacteria. d. allow filamentous methanogens to metabolize acetate within the interior of flocs.

ANS: B DIF: Moderate REF: 27.5 OBJ: 27.5b Explain the stages of standard wastewater treatment, including the key participation of microbial ecosystems.

MSC: Applying 36. A chicken producer in Georgia is considering installing a wetland rather than a traditional wastewater treatment facility to handle chicken manure and wastewater. Which of the following is an advantage of using a wetland? a. Wetlands do not contain microbes. b. Wetlands produce fewer odors than wastewater treatment facilities. c. The cost of a wetland is only slightly higher than the cost of a wastewater treatment facility. d. Wetlands do not take up much space.

ANS: B DIF: Moderate REF: 27.5 OBJ: 27.5b Explain the stages of standard wastewater treatment, including the key participation of

microbial ecosystems.

MSC:

Understanding

37. Photosynthesis in microbes converts carbon dioxide into a. biomass. c. ethanol. b. carbonate rock. d. nitrosamine.

ANS: A DIF: Easy REF: 27.6 OBJ: 27.6a Describe how microbes participate in the global cycling of carbon by converting carbon between its reduced and oxidized forms.

MSC: Understanding 38. What role do microbes play in the increase of atmospheric carbon dioxide seen in the graph below?

a. Microbial populations have been increasing since 1800, and this increase has led to increases in carbon dioxide levels. b. Microbes convert other elements in carbon dioxide and have caused increases in carbon dioxide levels. c. Microbial populations have been decreasing since 1800, and this decrease has led to increases in carbon dioxide levels. d. Microbes fix carbon dioxide and help limit increases of carbon dioxide in the atmosphere.

ANS: D DIF: Difficult REF: 27.6 OBJ: 27.6a Describe how microbes participate in the global cycling of carbon by converting carbon between its reduced and oxidized forms.

MSC: Analyzing 39. The fixed form of nitrogen (ammonium ion and ammonia) can be oxidized for energy by a. methanogens. c. lithotrophs. b. nitrifiers. d. fermenters.

ANS: B DIF: Easy REF: 27.6 OBJ: 27.6c Outline the unique roles of microbes in cycling different forms of nitrogen.

MSC: Understanding 40. Historically, N2 only entered the atmosphere as a result of nitrogen fixation by bacteria and archaea.

How has human technology affected nitrogen cycling? a. Humans genetically modified plants to allow them to fix nitrogen. b. Humans developed a method for artificially fixing nitrogen to generate fertilizers. c. Humans use nitrogen as a source of renewable energy. d. Human technology has had no effect on nitrogen cycling.

ANS: B DIF: Moderate REF: 27.6 OBJ: 27.6d Explain how human technology perturbs the global nitrogen cycle.

MSC: Understanding

41. CASE HISTORY In the fall of 2008, several individuals, many of them children, were sickened from the common food pathogen Salmonella enterica. Most infected individuals developed diarrhea, fever, and abdominal cramps 12–72 hours after infection, and symptoms lasted 4–7 days. Over the next six months, cases were reported from nearly all U.S. states, ultimately totaling 700 people. The curve of the outbreak (cases rising and then falling) followed the profile of a single-source epidemic, in which all infections are ultimately traced to one source. All cases of illness showed a common strain of the pathogen S. enterica serovar typhimurium. CDC researchers investigated the outbreak by comparing the food intake histories of ill persons with those of matched controls. They found a statistical association between illness and intake of peanut butter, eventually narrowed to a specific brand of peanut butter sold to institutions. As the epidemic grew, cases emerged in which the contaminated food product turned out to be crackers filled with peanut butter cream. Ultimately, the peanut butter and cream were traced back to peanuts from a single factory in Georgia.

Which best describes this outbreak of foodborne illness? a. It is an example of food spoilage. b. It is an example of a point-source epidemic. c. The origin of the outbreak is contamination of the peanut butter by a plant pathogen. d. If carefully examined, the peanut butter would have been noticeably “off ” in taste, smell, texture, or other observable characteristics.

ANS: B DIF: Moderate REF: Case History 27.2 OBJ: 27.4a Explain the difference between food spoilage and food contamination.

MSC: Understanding COMPLETION 1. Using organisms such as bacteria to neutralize pollutants from a contaminated site is referred to as ________.

ANS: bioremediation DIF: Easy REF: 27.1 OBJ: 27.1a Describe the various roles of microbes in natural ecosystems and the kinds of ecosystem services that microbes provide.

MSC: Remembering 2. The specialized relationship in which one member benefits while the other member is harmed is known as ________.

ANS: parasitism DIF: Easy REF: 27.2 OBJ: 27.2a Explain the different kinds of microbe-animal symbioses, including mutualism, synergism, commensalism, amensalism, and parasitism.

MSC: Understanding 3. An end result of mixed-acid fermentation products being converted into a gas in cattle is production of the greenhouse gas ________.

ANS: methane DIF: Easy REF: 27.2 OBJ: 27.2b Describe the digestive communities of animals.

MSC: Remembering

4. Moving microbes from the gut of a healthy person into a diseased colon to return normal function in a patient with recurrent Clostridium difficile infections is known as ________.

ANS: fecal transplant; bacteriotherapy; fecal bacteriotherapy DIF: Easy REF: 27.2 OBJ: 27.2c Explain how microbial communities contribute to human health.

MSC: Remembering 5. During the production of beer, fermentation produces ethanol and the gas ________.

ANS: carbon dioxide; CO2; CO2 DIF: Easy REF: 27.3 OBJ: 27.3b Outline the process of ethanolic fermentation in the production of beer and wine.

MSC: Remembering 6. Bacteria, such as Listeria monocytogenes, that are able to grow at refrigeration temperatures are referred to as ________.

ANS: psychrotrophs DIF: Moderate REF: 27.4 OBJ: 27.4c Describe the various physical and chemical approaches to food preservation.

MSC: Remembering 7. Organic molecules in lake water are consumed as food and combined with oxygen by ________.

ANS: bacteria DIF: Easy REF: 27.5 OBJ: 27.5a Describe the processes of the water cycle, and explain how human and industrial wastewater enter it. MSC: Remembering 8. In a wastewater treatment plant, the removal of large, solid debris such as sticks and dead animals occurs during ________ treatment.

ANS: preliminary DIF: Easy REF: 27.5 OBJ: 27.5b Explain the stages of standard wastewater treatment, including the key participation of microbial ecosystems.

MSC: Remembering 9. Carbon dioxide in the atmosphere traps solar heat in a process known as the ________.

ANS: greenhouse effect DIF: Easy REF: 27.6 OBJ: 27.6b Explain the implications of global carbon cycling for human health.

MSC: Remembering 10. Bacteria and archaea are the only organisms capable of converting the element ________ between its oxidation states.

ANS: nitrogen DIF: Moderate REF: 27.6 OBJ: 27.6c Outline the unique roles of microbes in cycling different forms of nitrogen.

MSC: Remembering SHORT ANSWER 1. Explain how the availability of oxygen in soil determines how microbes utilize organic compounds supplied by other organisms.

ANS: When oxygen is available, it is used as an electron acceptor during aerobic cellular respiration. When oxygen is not available, anaerobic electron acceptors are utilized. Organic compounds are broken down to carbon dioxide more rapidly when oxygen is available.

DIF: Moderate REF: 27.1 OBJ: 27.1b Explain how physical factors determine which microbes grow in a given habitat.

MSC: Understanding 2. Describe any differences between the primary producers in the ocean versus the primary producers on land.

ANS: Primary producers fix carbon dioxide and produce biomass for consumers. Within the ocean the main primary producers are photosynthetic bacteria and algae. On land, macroscopic plants are the primary producers.

DIF: Moderate REF: 27.1 OBJ: 27.1c Outline how microbes participate in the food chains of ocean, soil, and wetland.

MSC: Applying 3. Explain the location of the “dead zone” shown in the figure below. What causes this dead zone to appear annually during spring?

ANS: This dead zone is caused by drainage from the Mississippi River into the Gulf of Mexico. High levels of organic waste and nitrates from agricultural fertilizer allow algae to grow. When the large algae populations crash, bacteria consume the dead algae cells and use up all of the available oxygen in the process. Fish and invertebrates are unable to survive without oxygen and subsequently die off.

DIF: Difficult REF: 27.1 OBJ: 27.1d Explain the phenomenon of biochemical oxygen demand and the cause of dead zones.

MSC: Understanding 4. Describe how bacteria such as Lactobacillus species are used to produce yogurt.

ANS: Lactobacillus produces lactic acid, which leads to a decrease in the pH of milk. When the pH drops below 5, casein proteins within the milk become denatured and form a network of protein threads that capture other substances. The denatured casein and other trapped particles form the semisolid texture of yogurt, and the decreased pH prevents the growth of other microbes.

DIF: Easy REF: 27.3 OBJ: 27.3a Describe the roles of bacteria and fungi in the production of cheese and fermented soy foods.

MSC: Understanding 5. List two ways in which food fermentation benefits humans and provide one example for each.

ANS: Food fermentation can be used to preserve food. For example, acid buildup inhibits growth of bacteria in milk products. Food fermentation can improve the digestibility of meat and vegetable products. For example, microbes can break down fibrous macromolecules in vegetables to make them easier to digest. A third benefit is the addition of nutrients or flavors. For example, vitamin B12 is added by some microbes, such as yeast.

DIF: Easy REF: 27.3 OBJ: 27.3c Explain why fermented foods and beverages retain high food value.

MSC: Applying 6. Hannah leaves the milk out on the counter after breakfast one day. Eight hours later she realizes her mistake and puts the milk back in the refrigerator. The next morning she pours herself a glass of milk, takes a sip of the milk, and immediately spits it out. Was Hannah responding to food spoilage or food contamination? Explain your reasoning.

ANS: Food spoilage is responsible for changes in the taste of a food. In this case the milk was spoiled and had become sour. Food contamination typically goes unnoticed during consumption because the presence of microbial pathogens or toxins does not usually change the appearance of the food.

DIF: Moderate REF: 27.4 OBJ: 27.4a Explain the difference between food spoilage and food contamination.

MSC: Evaluating 7. What are the three factors that control the ways in which food spoils?

ANS:

The three factors that control how foods spoil are the nutrient content of the food, the species of microbes involved, and abiotic environmental factors.

DIF: Easy REF: 27.4 OBJ: 27.4b Outline the different processes of spoilage of dairy products, meat, seafood, and plant foods. Explain why different types of food spoil differently.

MSC: Understanding 8. Describe the carbon reservoir that cycles the most carbon through living bodies on Earth.

ANS: The atmosphere cycles most of the carbon used by living organisms. The atmosphere is a source of carbon dioxide that is converted into biomass through photosynthesis. The atmosphere also acts as a sink for carbon dioxide produced by heterotrophs.

DIF: Moderate REF: 27.6 OBJ: 27.6a Describe how microbes participate in the global cycling of carbon by converting carbon between its reduced and oxidized forms.

MSC: Understanding 9. Explain the pattern of groundwater nitrate contamination risk shown in the map below.

ANS: The highest risk of nitrate contamination occurs in highly cultivated areas in the United States. These high levels of nitrate are caused by nitrogenous fertilizers applied to agriculture. Bacterial ammonification of the nitrogenous fertilizer, followed by nitrification, generates nitrates.

DIF: Difficult REF: 27.6 OBJ: 27.6d Explain how human technology perturbs the global nitrogen cycle.

MSC: Analyzing 10. CASE HISTORY

In 1994, the city of Phoenix, Arizona, faced challenges to its water supply. In a desert, water is scarce, and quality is hard to maintain. The city’s water department needed to decrease its wastewater’s organic nitrogen content, which threatened the river downstream. A study proposed the construction of a wetland environment to receive the treated effluent from the Phoenix sewage plant. Over the next ten years, the city constructed a series of experimental wetlands, leading to the large-scale tres rios– Wetlands Project. By 2010, the constructed wetland encompassed 800 acres and filtered 170 million gallons per day. Besides controlling nitrogen and organic content, the wetland restores groundwater, offers a carbon offset (net CO2 removed from the atmosphere), and generates a wildlife-rich recreational area. The tres rios wetland now attracts beavers, bald eagles, and bobcats, as well as many human visitors.

Why might many different configurations of wetland have been constructed in order to achieve the desired microbial community and effect?

ANS: Physical factors such as oxygen, nutrient, and light availability influence microbial composition, as does the existing microbial community.

DIF: Moderate REF: Case History 27.1 OBJ: 27.1d Explain the phenomenon of biochemical oxygen demand and the cause of dead zones.

MSC: Analyzing 11. CASE HISTORY In the fall of 2008, several individuals, many of them children, were sickened from the common food pathogen Salmonella enterica. Most infected individuals developed diarrhea, fever, and abdominal cramps 12–72 hours after infection, and symptoms lasted 4–7 days. Over the next six months, cases were reported from nearly all U.S. states, ultimately totaling 700 people. The curve of the outbreak (cases rising and then falling) followed the profile of a single-source epidemic, in which all infections are ultimately traced to one source. All cases of illness showed a common strain of the pathogen S. enterica serovar typhimurium. CDC researchers investigated the outbreak by comparing the food intake histories of ill persons with those of matched controls. They found a statistical association between illness and intake of peanut butter, eventually narrowed to a specific brand of peanut butter sold to institutions. As the epidemic grew, cases emerged in which the contaminated food product turned out to be crackers filled with peanut butter cream. Ultimately, the peanut butter and cream were traced back to peanuts from a single factory in Georgia.

Describe some of the chemical and physical approaches normally used in the production and storage of a food like peanut butter, which are designed to reduce the possibility of outbreaks such as this one.

Give an example of a common scenario in which these precautions might fail.

ANS: Students should choose methods that are reasonable in context (i.e., modified atmosphere may be appropriate for peanut butter, but selecting freezing would not be reasonable for anyone with experience in buying or eating peanut butter). Answers may vary but should be logical. Similarly, failures may vary, but should be consistent with the method described—for example, a packaging breach that disturbs modified atmosphere.

DIF: Moderate REF: Case History 27.2 OBJ: 27.4c Describe the various physical and chemical approaches to food preservation.

MSC: Understanding