Kirby-Bauer disk diffusion test

Definition

The Kirby-Bauer disk diffusion test is a method used to determine the sensitivity of bacteria to specific antimicrobial agents. It involves placing antibiotic-impregnated disks on an agar plate inoculated with the test organism and measuring zones of inhibition.

5 Must Know Facts For Your Next Test

1. Zones of inhibition around disks indicate the effectiveness of antibiotics.
2. Results are interpreted using standardized charts that correlate zone size with susceptibility categories (susceptible, intermediate, resistant).
3. Mueller-Hinton agar is commonly used for this test due to its reproducibility and ability to support the growth of most pathogens.
4. The test requires incubation at 35°C for 16-18 hours before interpreting results.
5. It’s a qualitative rather than quantitative method, providing categorical rather than exact minimum inhibitory concentration (MIC) values.

Review Questions

• What type of agar is most commonly used for the Kirby-Bauer disk diffusion test?
• How are the results from a Kirby-Bauer disk diffusion test interpreted?
• Why is it important to incubate the plates at a specific temperature and time?

Related terms

Minimum Inhibitory Concentration (MIC): The lowest concentration of an antimicrobial that inhibits visible growth of a microorganism.

Antibiogram: A profile of antimicrobial susceptibility testing results for a specific microorganism.

Zone of Inhibition: The clear area surrounding an antibiotic disk where bacterial growth has been prevented.