Control of Microbial Growth Lab

SCI/250 v5

Control of Microbial Growth Lab Reporting Worksheet TITLE: The Control of Microbial Growth: Decontamination and Selective Toxicity Lab

PROBLEM: Individuals might present with persistent bacterial infections if the causative agent is not sensitive to antibiotics.

This experiment explores the sensitivity of a bacterial infection to first-line antibiotics. The experiment investigates the decontamination strategies applied to control bacterial growth.

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Control of Microbial Growth Lab Reporting Worksheet SCI/250 v5 Page 2 of 5

HYPOTHESIS: Information that is relevant to the problem and the concepts related to the lab problem The effectiveness of antibacterial compounds differs significantly depending on the sensitivity of bacteria to these agents. Determining the effectiveness of bacterial resistance to chemical compounds is central to managing infections.

Concepts related to the lab problem Selective toxicity – chemical compounds exert a toxic effect on pathogenic agents without harming the host cells.

These agents target specific components or parts of the pathogenic agent that are unique and different from the host’s cells.

Resistance – prolonged use of antibacterial compounds increase the risk of resistance. The pathogenic agent changes the target components of chemical compounds, thus rendering these agents ineffective. The mutated cells may proliferate leading to antibacterial resistance (Kumavath, 2017).

Variables and their relationships The variables in this experiment were the antimicrobial discs and the zone of inhibition. The antimicrobial discs were the independent variables. They were placed on different regions on the surface of the agar plates. The zone of inhibition was the dependent variable being observed. The zone of inhibition was influenced by the type of antimicrobial agent and the microbes on the agar plates.

Developing a hypothesis that predicts the relationship between the variables being studied The zone of inhibition is greatest in diffusion discs with highly concentrated antimicrobial agents.

METHOD: Define and describe each variable and how it was changed throughout the lab.

The experiment involved comparing the sensitivity of two different organisms to the same chemical agent. The antimicrobial agent was the independent variable in this experiment. The zone of inhibition is the dependent variable in this experiment. This zone is defined as the circular region around the spot where diffusion discs containing antimicrobial compounds are placed. The chemical compounds affect bacterial growth, thus inhibiting colony formation. This zone reflects the sensitivity of bacteria to chemical agents.

Summary of experiment This experiment involved preparing the Mueller-Hinton agar plates, preparation of inoculum, and inoculation of the afar plates with the test organisms. The diffusion discs were impregnated with an antimicrobial drug and placed on the surface of the agar. The agar plates were incubated at 35oC for 24 hours. The zones of inhibition were then measured with a ruler. The inhibition zones were recorded on a table for comparison.

Describe some of the observations you made?

The organisms used in the experiment were E.coli and S. aureus. These organisms demonstrated sensitivity to antimicrobial agents. However, gram-positive organisms were more sensitive to antimicrobial agents than gram-

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Control of Microbial Growth Lab Reporting Worksheet SCI/250 v5 Page 3 of 5 negative organisms. The zone of inhibition was greatest in discs with a high concentration of the antimicrobial agent.

Which parts of the lab required you to think more than others and required more time? Which parts were simple and completed easily?

The complex part of the experiment is impregnating the discs with an antimicrobial agent. The right concentration of antimicrobial compound was prepared. This process was challenging since variations in concentration might lead to bias.

DATA & RESULTS: What relationships did you notice between the variables you examined? When you changed the variable(s), how did the other(s) change?

A high concentration of antimicrobial chemicals produced the largest zone of inhibition. S. aureus was more sensitive to the antimicrobial agent than E. coli.

Any patterns between the variables The organisms demonstrated greater sensitivity to high antimicrobial concentrations than low antimicrobial concentrations.

DISCUSSION: During your lab, what happened that might have impacted the accuracy of your data? Did the simulation alert you that an error was occurring? If so, how did you resolve it?

The experiment revealed significant variations in the inhibition zones for different antimicrobial agents. However, the antimicrobial agents did not produce perfect inhibition zones due to overlapping (Kumavath, 2017). This problem occurred due to antimicrobial discs placed close to each other on the agar surface. The radius of the partial zones was doubled to get the diameter.

CONCLUSION: Describe how the lab results compare to the background information you discussed before.

The results confirmed the hypothesis that a highly concentrated antimicrobial agent contributes a greater zone of inhibition than a low concentration of antimicrobial chemicals. The results also show that some bacteria demonstrate greater sensitivity to certain chemical compounds than others.

How is the information from this lab related to the course student learning outcome? What knowledge has the lab supported you with learning related to this course student learning outcome?

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Control of Microbial Growth Lab Reporting Worksheet SCI/250 v5 Page 4 of 5 Information from this lab is significant to the course learning outcomes. It revealed how researchers control microbial growth to determine the effectiveness of certain chemical compounds. Importantly, the experiment reveals how chemical agents suppress microbial growth, thus reducing the risk of bacterial infection.

What additional scientific things do you wonder about after completing and writing about your lab experience?

The question that lingers in this experiment is whether some antimicrobial agents inhibit bacterial growth nonselectively. Further experimentation is needed to determine the impact of such agents in pathogenic bacteria and normal flora.

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Control of Microbial Growth Lab Reporting Worksheet SCI/250 v5 Page 5 of 5 References

Parker, N., Schneegurt, M., Tu, A.-H. T., Forster, B. M., Lister, P., OpenStax College, & American Society for Microbiology. (2017). Microbiology. OpenStax.

Kumavath, R. (2017). Antibacterial agents. InTech.

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