Final answer:
The Kirby-Bauer susceptibility test indicates that the microbe does not grow in the presence of the antimicrobial agents when a zone of inhibition is present. The test determines the susceptibility or resistance of a pathogen but does not inform on bactericidal versus bacteriostatic activity or drug potencies.
Step-by-step explanation:
In a Kirby-Bauer susceptibility test, the presence of a zone of inhibition around disks containing antimicrobial agents indicates that the microbe does not grow in the presence of the agents. Specifically, the size of the zone of inhibition is measured, and its diameter is compared to a standardized chart to determine whether a bacterial pathogen is susceptible or resistant to the antimicrobial agent. It's important to note that while this test is helpful in identifying which antibiotics may thwart a particular microbe, it does not differentiate between bacteriostatic (mere inhibition of bacterial growth) and bactericidal (killing of bacteria) effects, nor can it be used to compare the potencies or efficacies of different antimicrobial drugs directly.
Antimicrobial susceptibility testing (AST), such as the Kirby-Bauer disk diffusion test, is critical in the clinical laboratory setting to guide appropriate antibiotic therapy. However, to determine the exact minimum inhibitory concentration (MIC) or minimal bactericidal concentration (MBC) of an antimicrobial agent, additional tests like the dilution method are necessary.