important feature of antibiotics



Course: C453


EMP1 Task 3 Template


*Note: The video demonstrations and links to the instructional pdfs for the experiment are found in Unit 7, Module 21 of the course material.


Section I: Introduction

Explain why selective toxicity is an important feature of antibiotics and discuss the relative benefits of broad-spectrum and narrow-spectrum antibiotics.


· Note: Please see these sections of the course material: Unit 4, Module 10, Lesson 1: Spectrum of Activity and Unit 4, Module 10, Lesson 2: Mechanisms of Antibacterial Drugs. You will need to discuss the importance of selective toxicity, in addition to the benefits of broad-spectrum and narrow-spectrum antibiotics.


Section II: Materials and Methods

Describe in sufficient detail the steps you followed to complete the Kirby-Bauer diffusion test. Note: Include any changes from the normal protocol that might have been incorporated into your experiment.

Section III: Results

Provide the recorded observed results of the Kirby-Bauer diffusion test, including the zone of inhibition measurements and your interpretation of the zone of inhibition measurements (e.g., resistant, intermediate, susceptible) for each antibiotic using Data Table for the task.


Note: You may use the “Data Table” to record your results. You can find this document in the Task 3 instructions after clicking on the Task 3 assessment link.


Note: You will need to include zone of inhibition measurements for your report. “No growth on the plate” will not be an acceptable response. If you have no growth in an area of the plate around a given antibiotic, you can measure diameter of the entire area around that antibiotic and can note that measurement as your result.

Section IV: Discussion

Based on your recorded results from the Kirby-Bauer diffusion test, explain whether each of the following antibiotics would be a reasonable choice for treating S. epidermidis: 

•  penicillin

•  novobiocin

•  gentamicin


Note: To complete this part of Task 3, you will need to state whether each antibiotic would be an effective treatment for the bacterium that you tested. This determination should be solely based on your measured zone of inhibition results and your determination of where those zone of inhibition measurements fall within the susceptibility zones included as part of Data Table 3. Based on the results that you obtained, would you recommend the antibiotic for treatment of an infection with that bacterium?


Section V: Sources

Acknowledge sources, using in-text citations and references, for content that is quoted, paraphrased, or summarized.


Your submission must be your original work. No more than a combined total of 30% of the submission and no more than a 10% match to any one individual source can be directly quoted or closely paraphrased from sources, even if cited correctly. An originality report is provided when you submit your task that can be used as a guide.

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