What is the significance of the Kirby-Bauer test?

The Kirby-Bauer test is significant because it specifically determines the susceptibility of bacteria to antibiotics through a standardized method. In this test, a bacterial isolate is spread evenly over a Mueller-Hinton agar plate, and then discs containing specific antibiotics are placed on the surface of the agar. As the bacteria grow, the antibiotics diffuse into the agar, creating a gradient. The effectiveness of each antibiotic is indicated by a clear zone around the disc, known as the zone of inhibition, where bacterial growth has been prevented. The diameter of this zone is measured and compared to standardized tables to categorize the bacteria as susceptible, intermediate, or resistant to the antibiotic in question. This information is crucial for guiding effective treatment options for infections and is a cornerstone of clinical microbiology in evaluating antimicrobial therapy.