A standardized disk diffusion test used to determine antibiotic susceptibility is called

A standardized disk diffusion test used to determine antibiotic susceptibility is called

• A. Bacteriostatic
• B. Minimum Inhibitory Concentration (MIC)
• C. Kirby-Bauer Test
• D. Bactericidal

Answer: (C)

The Kirby-Bauer disk diffusion method is the standardized way microbiology labs assess how susceptible a bacterium is to antibiotics. In this test, a bacterial lawn is spread on Mueller-Hinton agar and paper disks containing different antibiotics are placed on the surface. After incubation, clear zones—areas where bacteria didn’t grow around a disk—indicate inhibition by that drug. The size of each zone is measured and compared to established guidelines to determine if the organism is susceptible, intermediate, or resistant to each antibiotic. The method is standardized to ensure consistent results across labs: fixed agar depth, a uniform inoculum, standard disk sizes, and specific incubation conditions. This standardization is what makes the disk diffusion approach a reliable way to determine antibiotic susceptibility. It’s different from the minimum inhibitory concentration, which identifies the lowest drug concentration that prevents growth in liquid media, and from descriptions of whether an antibiotic is bacteriostatic or bactericidal, which refer to how the drug affects bacteria rather than how susceptible the bacteria are to treatment.

The Kirby-Bauer disk diffusion method is the standardized way microbiology labs assess how susceptible a bacterium is to antibiotics. In this test, a bacterial lawn is spread on Mueller-Hinton agar and paper disks containing different antibiotics are placed on the surface. After incubation, clear zones—areas where bacteria didn’t grow around a disk—indicate inhibition by that drug. The size of each zone is measured and compared to established guidelines to determine if the organism is susceptible, intermediate, or resistant to each antibiotic. The method is standardized to ensure consistent results across labs: fixed agar depth, a uniform inoculum, standard disk sizes, and specific incubation conditions. This standardization is what makes the disk diffusion approach a reliable way to determine antibiotic susceptibility. It’s different from the minimum inhibitory concentration, which identifies the lowest drug concentration that prevents growth in liquid media, and from descriptions of whether an antibiotic is bacteriostatic or bactericidal, which refer to how the drug affects bacteria rather than how susceptible the bacteria are to treatment.