Kirby-Bauer Test Procedures and Principles

The Kirby-Bauer disk diffusion test is a standardized method to determine the susceptibility of bacteria and fungi to antimicrobial compounds. It guides the selection of antimicrobials for treating infections. The test involves placing antimicrobial disks on an agar medium inoculated with microorganisms. After incubation, the presence of inhibition zones indicates susceptibility. The procedure requires specific materials and adherence to guidelines like CLSI M100. Accurate measurement and interpretation of results are crucial. Hardy Diagnostics provides resources and products for conducting these tests.

What is the primary purpose of the Kirby-Bauer disk diffusion test?

• To test the effectiveness of vaccines

• To measure the growth rate of bacteria

• To determine the susceptibility of bacteria and fungi to antimicrobial agents

• To identify the type of bacteria present

What does a clear zone around an antimicrobial disk indicate?

• The agar medium is contaminated

• The test was performed incorrectly

• The microorganism is susceptible to the antimicrobial agent

• The microorganism is resistant to the antimicrobial agent

Which document provides the current breakpoints for bacterial pathogens?

• CLSI M02

• FDA STIC

• Hardy Diagnostics Manual

• CLSI M100

Which of the following is NOT a material needed for the Kirby-Bauer test?

• Antimicrobial disks

• Sterile cotton swabs

• Mueller Hinton agar plates

• Petri dish covers

What is the purpose of adjusting the suspension to a 0.5 McFarland standard?

• To change the color of the suspension

• To increase the growth rate of bacteria

• To sterilize the suspension

• To ensure the correct concentration of the inoculum

How should the antimicrobial disks be placed on the agar plate?

• Only near the edges of the plate

• Directly on top of each other

• At least 24 millimeters apart

• Randomly across the plate

What is the recommended incubation temperature for the plates?

• 25 degrees Celsius

• 40 degrees Celsius

• 30 degrees Celsius

• 35 degrees Celsius

What should be done if individual colonies are visible instead of a confluent lawn?

• Increase the incubation time

• Repeat the test with a higher inoculum concentration

• Decrease the temperature

• Add more antimicrobial disks

How are the zones of inhibition measured?

• By weighing the agar plate

• With a sliding caliper or ruler

• Using a thermometer

• With a microscope

What should be referenced to interpret the zone measurements?

• Local laboratory standards

• FDA guidelines

• Hardy Diagnostics catalog

• CLSI M100 breakpoint tables