Microbiology a clinical approach 2nd edition strelkauskas test bank

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Microbiology: A Clinical Approach, Second Edition Chapter 8 Emerging and Re-Emerging Infectious Disease Question Bank

Multiple Choice

1.

A. B. C. D. E.

Which of the following is not a potential circumstance that would favor re-emerging infectious diseases?

Loss of health care infrastructure because of political restructuring Deterioration of living standards because of civil war Accidental release from a research lab of a genetically engineered strain of bacteria that is highly contagious Appearance of an epidemic which damages host immune responses Loss of health care infrastructure and deterioration of living standards because of political restructuring and civil war

Answer: C Feedback: Accidental release of a genetically engineered, highly contagious strain of bacteria would create the potential for an emerging disease, not a re-emerging one. An emerging infectious disease is one whose incidence has increased in the last 30 years or threatens to increase in the near future. Emerging diseases may have not previously been seen in humans or only rarely seen. A re-emerging infectious disease is one that was previously controlled but has now returned. Loss of health care infrastructure, deterioration of living standards, and an epidemic of a disease that damages host immune responses would all favor the re-emerging infectious diseases.

Difficulty: 3

2.

A. B. C. D. E.

A new virus has been identified by DNA sequencing methods in a remote location in the South Pacific. The World Health Organization is very concerned because infection with this virus has a death rate of 20% of all infected individuals and no vaccine is available.

This is an example of a(n) _____ disease.

Re-emerging infectious Latent Prion Emerging infectious Vector-borne

Answer: D Feedback: An emerging infectious disease is one whose incidence has increased in the last 30 years while a re-emerging infectious disease is one that has reappeared after a decline in 1

incidence. A latent disease is one in which symptoms reappear long after the initial infection, a prion disease is caused by abnormally folded, infectious prion proteins, and vector-borne diseases are transmitted by vectors.

Difficulty: 1

3.

A. B. C. D.

Developing nations have seen a dramatic decrease in the number of fatal infectious diseases in the twentieth century, attributed primarily to the Emergence of multi-drug resistant bacteria Development of herd immunity Development of antibiotics Rising numbers of hospital staff

Answer: C Feedback: The discovery of penicillin, sulfa drugs, and a host of other antibiotics produced this decrease. The development of herd immunity and rising numbers of hospital staff did not produce an marked benefit, while the emergence of multi-drug resistant bacteria can result in an increase in the number of fatal infections.

Difficulty: 2

4.

A. B. C. D. E.

The potential for a Lyme disease outbreak is closely associated with The number of deer mice residing in a particular region The number of mosquitos breeding in the woods The proximity of piggeries to human populations Crowded housing conditions The number of deer residing in a particular region

Answer: E Feedback: The vector for Lyme disease is the deer tick. The number of deer residing in a particular region affects the number of ticks and the potential for outbreaks of Lyme disease. A greater number of deer results in a greater number of ticks and the potential for increased transmission of Lyme disease.

Difficulty: 1

5.

A. B. C. D. E.

Which of the following is a mismatched pair?

SARS: South America Ebola: Africa HIV: Africa Nipah: Malaysia Avian influenza: China

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Answer: A Feedback: SARS emerged in China where a previously unrecognized animal coronavirus adapted and became transmissible to and among humans. Novel infectious disease can emerge in any part of the world at any time. Other examples include HIV and Ebola from Africa, avian influenza from China, Nipah from Malaysia, and Hantavirus from South America.

Difficulty: 1

6.

A. B. C. D.

Which of the following describes the process of recombination?

Synthesis of a nearly perfect copy of a molecule Portions of chromosomes from different pathogens link Single base in genetic material converts to another Two chromosomes from different pathogens form a pair

Answer: B Feedback: Recombination is the combining of DNA from two different cells, resulting in a recombinant DNA molecule.

Difficulty: 1

7.

A. B. C. D.

Which of the following describes the process of replication?

Synthesis of a nearly perfect copy of a molecule Portions of chromosomes from different pathogens link Single base in genetic material converts to another Two chromosomes from different pathogens form a pair

Answer: A Feedback: Replication is when a nearly perfect copy of a molecule is synthesized.

Difficulty: B=1

8.

A. B. C. D.

Which of the following describes the process of reassortment?

Synthesis of a nearly perfect copy of a molecule Portions of chromosomes from different pathogens link Single base in genetic material converts to another Two chromosomes from different pathogens form a pair

Answer: B Feedback: Re-assortment occurs when whole gene segments are swapped during co-infection with two pathogens.

Difficulty: 1

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9.

A. B. C. D.

Which of the following describes the process of point mutation?

Synthesis of a nearly perfect copy of a molecule Portions of chromosomes from different pathogens link Single base in genetic material converts to another Two chromosomes from different pathogens form a pair

Answer: C Feedback: Point mutations occur when single nucleotide bases of the DNA sequence change.

This can be due to a substitution of one base for another, or by insertion or deletion of a nucleotide base in the sequence.

Difficulty: 1

10.

A. B. C. D. E.

SARS is transmitted by all of the following mechanisms except Droplet Fomite Direct contact Mosquitoes Aerosol

Answer: D Feedback: SARS can be transmitted by direct contact, droplet (including aerosol), and fomite, all forms of contact transmission. It is deposited on the respiratory mucosal epithelium where it initiates infection. It is not transmitted by vector.

Difficulty: 1

11.

The _____ of the SARS coronavirus is used to bind to receptors on the host cell membrane.

A. Small membrane protein (M protein) B. Nucleocapsids protein C. RNA D. Spike protein (S protein) Answer: D Feedback: The SARS virus enters host cells by attaching spike proteins present on the virion to receptors on the host plasma membrane. M protein, nucleocapsids protein, and RNA are not involved.

Difficulty: 1

12.

Which of the following is not true of the SARS coronavirus?

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A. B. C. D.

It is a single-stranded viral RNA There is a vaccine available It causes pneumonia It initiates infection on mucosal epithelia of the respiratory tract

Answer: B Feedback: SARS is a single-stranded RNA virus that first infects mucosal cells in the lungs and can cause pneumonia. There is no vaccine available for SARS. Difficulty: 1

13.

A. B. C. D. E.

Which of the following is a target for the virus that causes viral hemorrhagic disease?

Monocytes Dendritic cells Endothelial cells Hepatocytes All of the choices

Answer: E Feedback: Viral Hemorrhagic Fever (VHF) viruses target monocytes, dendritic cells, endothelial cells, hepatocytes, and adrenal cortical cells. They use endocytosis as the mechanism of penetration and cause varying degrees of cell destruction.

Difficulty: 1

14.

A. B. C. D. E.

There are no vaccines available for any of the following except SARS HIV Transmissible spongiform encephalitis Diphtheria Marburg virus

Answer: D Feedback: There is a vaccine for diphtheria. It is part of a vaccine packet called DPT which contains toxoids of diphtheria and tetanus, and killed whole cells of the pertussis pathogen. There is currently no vaccine for SARS, HIV, Transmissible spongiform encephalitis, or Marburg virus.

Difficulty: 1

15.

A. B.

The primary host of the West Nile virus is Birds Mosquitoes 5

C. D. E.

Humans Horses Monkeys

Answer: A Feedback: Birds are the primary host of the West Nile virus, and it is spread from bird to bird by mosquitoes. Humans, and animals such as horses, are incidental hosts and they can be infected by mosquitoes carrying the virus.

Difficulty: 1

16.

A. B. C. D.

All of the following are possible modes of transmission for the West Nile virus except Tainted blood transfusion Inhalation of rodent excrement Mosquito bites Infected organ transplant

Answer: B Feedback: West Nile fever is a blood-borne disease that could be transmitted by mosquito bite, tainted blood transfusion, and infected organ transplant. It is not transmitted via the fecal-oral route and would not be present in rodent feces.

Difficulty: 1

17.

A. B. C. D. E.

All of the following are characteristics of Ebola hemorrhagic fever except Circulatory shock Possibility of transmission from human to human Effective vaccine if received in advance of exposure Disseminated intravascular coagulation (DIC) Petechial hemorrhaging

Answer: C Feedback: There is currently no approved vaccine for Ebola, although several experimental drugs have been used in the treatment of infected healthcare workers during the 2014 outbreak.

Characteristics of VHF infection include circulatory shock, DIC, and petechial hemorrhaging.

All VHF viruses are transmissible from human to human, usually through direct contact with infected blood or bodily fluids.

Difficulty: 1

18.

A. B.

Which of the following groups is susceptible to tuberculosis (TB)?

Malnourished individuals AIDS patients 6

C. D. E.

Immunocompromised individuals living in long-term care facilities Alcoholics All of the choices

Answer: E Feedback: Individuals with reduced immune defenses are more susceptible to infection with TB. This includes those who are malnourished, alcoholics, and immunocompromised individuals such as AIDS patients.

Difficulty: 1

19.

A. B. C. D. E.

Which of the following is not an explanation for the re-emergence of TB? Failure of patients with TB to take all of there prescribed antibiotics An increase in the number of elderly living in nursing homes An increase in the rodent population in urban areas An increase in the number of immigrants born in areas where TB occurs The HIV/AIDs epidemic

Answer: C Feedback: Tuberculosis is mainly spread through droplet transmission and is not transmitted by rodents. Factors contributing to the re-emergence of TB include inappropriate treatment resulting in the evolution of antibiotic resistant TB stains, and an increase in susceptible individuals due to poor socioeconomic conditions in areas where TB occurs, and rising numbers of immunocompromised individuals such as HIV/AIDS patients and the elderly in nursing homes.

Difficulty: 2

20.

A. B. C. D. E.

Which of the following epidemics was caused by an H1N1 virus?

Asian influenza Hong Kong influenza Spanish influenza Swine influenza of 2009 Spanish influenza and Swine influenza of 2009

Answer: E Feedback: H1N1 viruses caused both the Spanish Flu epidemic of 1918 and the Swine Flu epidemic of 2009. The Asian influenza epidemic of 1957 was caused by H2N2 virus and the Hong Kong influenza epidemic of 1968 was caused by H3N2 virus.

Difficulty: 1

21.

Which of the following is not a characteristic of transmissible spongiform encephalitis diseases?

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A. B. C. D. E.

They cause neurodegeneration They are treated with proteases inhibitors They require long incubation periods The earliest documented cases were in the Fore people of New Guinea They are caused by abnormal PrPSCprions

Answer: B Feedback: There is no treatment for transmissible spongiform encephalitis disease. These diseases are caused by infectious, abnormal prion proteins, have long incubation periods, and cause neurodegeneration. The first observed prion disease in humans was kuru, which occurred in the Fore people of New Guinea.

Difficulty: 1

22.

A. B. C. D. E.

Which is not a characteristic of prions?

Resistant to degradation by proteinases Found mainly on outer membranes of nerve cells.

Resistant to autoclave treatment.

Unable to pass through the intestinal wall Resistant to autoclave treatment and unable to pass through the intestinal wall

Answer: D Feedback: Prions are able to pass through the intestinal wall. They are also resistant to degradation by proteinases and autoclave treatment, and are mainly found on the outer membranes of nerve cells.

Difficulty: 1

23.

A. B. C. D. E.

Which of the following choices regarding Creutzfeldt–Jacob disease (CJD) is a mismatched pair?

Iatrogenic form: blood transfusion Mad cow disease: epidemic in humans Familial form: genetically inherited Prognosis: death within 12 months of first signs Brain morphology: plaques

Answer: B Feedback: Mad cow disease (BSE) was not a human epidemic as only a few humans ever came down with the disease. The iatrogenic form of CJD is transmitted through medical treatments such as blood transfusions and corneal transplants. Familial CJD is genetically linked to mutations in the genes coding for normal prions. All forms of CJD exhibit plaque deposits in the brain and death usually occurs within 12 months after the first signs of disease appear.

Difficulty: 1

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Reference: Figure 1. VHF pathogenesis.

Use the figure below to answer the following questions.

24.

In the figure which letter (A to E) indicates virus particles?

Answer: D Feedback: Virus particles infect macrophages and dendritic cells. Chemokines recruit more macrophages to the site and these also become infected. Soluble factors are released, acting both locally and systemically, resulting in lymphocyte apoptosis and increased endothelial porosity and edema.

Difficulty: 1 Refer to: Figure 1. VHF pathogenesis.

25.

In the figure which letter (A to E) indicates a macrophage?

Answer: E Feedback: Virus particles infect macrophages and dendritic cells. Chemokines recruit more macrophages to the site and these also become infected. Soluble factors are released, acting both locally and systemically, resulting in lymphocyte apoptosis and increased endothelial porosity and edema.

Difficulty: 1 9

Refer to: Figure 1. VHF pathogenesis.

26.

In the figure which letter (A to E) indicates recruitment by chemokines?

Answer: C Feedback: Virus particles infect macrophages and dendritic cells. Chemokines recruit more macrophages to the site and these also become infected. Soluble factors are released, acting both locally and systemically, resulting in lymphocyte apoptosis and increased endothelial porosity and edema.

Difficulty: 1 Refer to: Figure 1. VHF pathogenesis.

27.

In the figure which letter (A to E) indicates apoptosis?

Answer: B Feedback: Virus particles infect macrophages and dendritic cells. Chemokines recruit more macrophages to the site and these also become infected. Soluble factors are released, acting both locally and systemically, resulting in lymphocyte apoptosis and increased endothelial porosity and edema.

Difficulty: 1 Refer to: Figure 1. VHF pathogenesis.

28.

In the figure which letter (A to E) indicates production of edema?

Answer: A Feedback: Virus particles infect macrophages and dendritic cells. Chemokines recruit more macrophages to the site and these also become infected. Soluble factors are released, acting both locally and systemically, resulting in lymphocyte apoptosis and increased endothelial porosity and edema.

Difficulty: 1 Refer to: Figure 1. VHF pathogenesis.

Essay

29.

Bovine spongiform encephalitis seems to be related to scrapie, a disease in sheep, and to Creutzfeldt-Jacob disease in humans. Compare and contrast BSE and CJD. 10

Answer: Prion diseases, known as transmissible spongiform encephalopathy (TSE), are a group of animal and human neurodegenerative diseases which are caused by infectious, abnormally folded prion proteins that then cause normal prions to fold improperly. These diseases are fatal and are characterized by long incubation periods and a complex neuropathology including spongiform effects and plaque deposits in brain tissue.

TSE in sheep is known as scrapie and in cattle as Bovine spongiform encephalitis (BSE).

BSE was first recorded in 1986 and was attributed to cattle feed that had been supplemented with sheep brains from sheep infected with scrapie. BSE was transmitted to humans by consumption of contaminated food, causing a new form of human TSE known as variant CJD (vCJD) which was first recorded in 1996.

Creutzfeldt-Jacob disease (CJD) is a human form of TSE which can occur spontaneously, can be genetically linked to mutations in the genes coding for normal priors, or can be transmitted through medical treatments such as blood transfusions and cornea transplants. It is usually seen in individuals of 55 to 75 years old, has an incubation period of 3 to more than 20 years, and usually causes death within 12 months of the first signs of the disease appearing.

Variant CJD differs from CJD in a number of ways. It occurs in younger individuals, those between 16 and 39 years old, the disease takes longer to progress and results in larger plaque deposits in the brain.

Difficulty: 2

30.

Name and describe four different transition patterns that emerging diseases have followed through history. Provide an example for each.

Answer: The four different transition patterns of emerging disease are crowd, war or trade, exploration and global urbanization. Crowd transition occurs when crowded living conditions facilitate transmission of both human-derived and zoonotic diseases. An example of this is measles which was confined to cattle 7000 years ago and then diverged to infect only humans.

War or trade transmission occurs when remote civilizations merge as a result of war or trade, promoting the exchange of infections and vectors. An example of this is typhus which was first reported during the Peloponnesian War. Exploration transition occurred when worldwide exploration and colonization introduced new diseases to areas never before affected by certain diseases. An example is the introduction of syphilis to Pacific island populations by Captain Cook and his crew. Global urbanization transition is currently occurring and where expanding, heavily populated settlements combined with poverty, social upheaval, air travel, technological development, deforestation, and climate changes are contributing to the emergence and reemergence of transmissible diseases. An example of this is SARS which became transmissible to and among humans in the 1990s, emerging in China and spreading to cause outbreaks in Hong Kong, Singapore, Vietnam, and Canada.

Difficulty: 2

11

31.

Where did the Hantavirus originate and how is it transmitted to humans? Explain the factors that contributed to the outbreak of Hantavirus in the southwestern region of the USA in 1993.

Answer: The Hantavirus originated in rodent populations in South America and spread to rodents in the southwestern region of the United States. The virus is transmitted through rodent excrement which, when inhaled by humans, causes acute respiratory disease. The 1993 outbreak of Hantavirus in southwestern USA occurred due to a surge in the deer mouse population that harbored the virus. The population increase was linked to a surplus of pine nuts, a staple food for deer mice, in that season and a subsequent increase in human exposure to rodent feces.

Difficulty: 2

32.

What are the three molecular processes that contribute to viral diversity? Describe each process and explain why these mechanisms are of concern.

Answer: The three molecular processes that contribute to viral diversity are mutation, recombination, and re-assortment. Mutation is a change in the nucleotide sequence which occurs when errors during nucleic acid replication result in substitution, addition, or deletion of nucleotides. Recombination is a rare event in which foreign genetic material gets incorporated into the viral genome. Re-assortment is where gene segments from two co-infecting viruses are redistributed to form new strains. These mechanisms are of concern because they can give rise to new biological properties of the virus such as new virulence characteristics or new host range specificities.

Difficulty: 3

33.

Describe two hurdles to the interspecies transfer of viruses and how these may be overcome. Which viruses are most effective at accomplishing this? Provide examples.

Answer: The two hurdles to interspecies transfer are first, that the virus must adapt to replicate successfully in the new host species, and second, that the virus must acquire the capacity to be transmitted among individuals of the new host species. The hurdles are overcome by alterations to the genetic makeup of the virus and this occurs through the molecular mechanisms of point mutation, recombination, and re-assortment. RNA viruses are the most effective at overcoming these hurdles as they are the best adapted to enable these molecular mechanisms generate viral diversity. Examples of such viruses include the influenza virus, SARS coronavirus, and viral hemorrhagic fever viruses.

Difficulty: 3

34.

Identify and explain four different factors that have contributed to the re-emergence of tuberculosis.

12

Answer: Factors contributing to the re-emergence of TB include an increase in the number of immunocompromised individuals, an aging population, poor socioeconomic conditions, and the development of drug resistance. An increasing number of immunocompromised individuals, such as the increased number of AIDS patients, has resulted in a greater number of individuals susceptible to TB. An aging population with an increased number of residents in nursing homes has also increased the number of cases. This is due to reactivation of latent TB infections in the elderly that become active cases, exposing other immunocompromised individuals to infection in an environment with a high concentration of susceptible individuals. Poor socioeconomic conditions also contribute. The risk of infection is increased in areas with high levels of poverty and crowded housing, where immune competence is often compromised by poor nutrition, drug abuse, and alcoholism. Migration of individuals from geographic areas with a high prevalence of TB can also contribute to increasing numbers of active cases. The development of drug resistance is a major factor in the re-emergence of TB. This is facilitated by inappropriate treatment as if patients do not follow the prescription regimen it not only increases the period of infectivity but also increases the chance that drug resistance will evolve. Both multi-drug resistant TB (MDR-TB) and extensively drug resistant TB (XDR-TB) are now seen in many countries across the world.

Difficulty: 3

35.

Could there be a connection between global warming and the dissemination of deadly strains of avian influenza? Explain your answer.

Answer: Global warming will have an impact on the migratory patterns of birds and as such could affect the migration of birds harboring the avian influenza virus (H5N1), spreading this virus to new geographical regions, individuals and species. H5N1 is one of the most potentially devastating emerging infections as it has an extremely high rate of mutation, can acquire genes from other viruses, and has a very high mortality rate. It is already capable of infecting humans although it has yet to become transmissible among humans. Of particular concern is the potential for co-infection of pigs with both avian and human influenza, which could result in gene reassortment, and produce a virus that would be extremely virulent and transmissible in humans.

Difficulty: 3

36.

Explain which measures led to the development of resistance to amantadine and rimantadine in the H5N1 influenza virus and why this resistance is a problem. Are there any alternative drugs to combat H5N1 and, if so, could sufficient protection be provided if there was an influenza pandemic?

Answer: The antiviral drugs amantadine and rimantadine are no longer effective against H5N1 as these drugs were administered in high doses to infected birds in an attempt to control influenza in birds in Asia. This did little to control the virus in birds, but instead fostered the development of resistance to these drugs. This is a problem as the amantadine and rimantadine 13

are among the few antiviral drugs available to combat influenza infections. An alternative drug is Tamiflu, which has some effect on H5N1. However, there is a worldwide shortage of this drug and there would be an insufficient supply in the event of a pandemic, resulting in a high mortality rate.

Difficulty: 3

37.

Explain the term “incubator” as it applies to an influenza pandemic involving pigs.

Answer: Pandemics usually arise when gene re-assortment between two different influenza strains occurs, giving rise to a new influenza variant to which the population is not immune.

Gene re-assortment requires a cell to be infected with both viral types simultaneously, such as with both the avian and human influenza strains. As pigs can be infected with both these viruses, they therefore provide a potential host in which incubation of both viruses could occur, providing an opportunity for gene re-assortment inside pig cells and the evolution of a new influenza variant capable of causing a pandemic.

Difficulty: 2

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