Question

You are testing whether a new antibiotic will be a good treatment choice for a patient with a staph infection. The Kirby-Bauer test using the organism from the patient shows a zone of inhibition of 15mm around the disk containing the drug. Clearly, the organism is susceptible. But you conclude from other studies that the drug will not be effective in the patient. What would make you draw this conclusion?

Answer 1

The Kirby-Bauer test which is also known as the disk-diffusion method, is the method by which antibiotic is used to test the susceptibility in determining what choice of antibiotics should be used when treating an infection.

The more the zone of inihibition, the more the antibiotic is effective in preventing the growth of the bacteria.

Since the other studies showed that the drug will not be effective in the patient, this shows that the zone of inhibition is low enough for the drug to be able to be effective in treating the patient with the infection due to this bacteria.

An effective antibiotive will give zone of inhibition of more than 25 mm. Since it is only 15mm for this antibiotic, thus it will not be effective.