Microbiology: A Systems Approach 4th Edition by Marjorie Kelly Cowan

Exercise 51

You have been directed to aseptically obtain a sample from a growth-free portion of the zone of inhibition in a completed Kirby-Bauer test and inoculate it onto a plate of nonselective medium.
a. After incubation at 37°C for 48 hours, you observe growth on the plate. Explain this result and how it impacts the analysis of the Kirby-Bauer test.
b. The drug tested was amoxicillin. Based upon your results, explain whether or not this is an effective drug choice for the treatment of an infection caused by this bacterium.