Kirby Bauer Disk Diffusion Test: Quiz and Flashcards

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

What is placed on the agar plate during the Kirby-Bauer assay?

How is antibacterial activity observed in the Kirby-Bauer disk diffusion test?

Why does the interpretation of the Kirby-Bauer assay provide only limited information on susceptibility and resistance?

Why can differences in zone sizes not be used to compare drug potencies or efficacies in the Kirby-Bauer test?

Kirby-Bauer Disk Diffusion Test

A method for determining the susceptibility of specific microbes to various antimicrobial drugs.
The test starts with a confluent lawn inoculated with a patient's isolated bacterial pathogen.

Assay Procedure

Filter paper disks impregnated with known amounts of antibacterial drugs are placed on the agar plate.
Antibiotic diffuses from the circular disk into the agar and interacts with the growing bacteria.

Zone of Inhibition

Antibacterial activity is observed as a clear circular zone of inhibition.
The diameter of the zone of inhibition helps determine the susceptibility or resistance of the bacterial pathogen to a particular drug.

Factors Affecting Zone of Inhibition

Drug solubility
Rate of drug diffusion through agar
Thickness of the agar medium
Drug concentration impregnated into the disk

Limitations of the Assay

Lack of standardization of the factors mentioned above.
Provides only limited information on susceptibility and resistance to the drugs tested.
Cannot distinguish between bacteriostatic and bactericidal activities.
Differences in zone sizes cannot be used to compare drug potencies or efficacies.

Learn about the Kirby-Bauer disk diffusion test, a method used to determine the susceptibility of microbes to antimicrobial drugs. This quiz covers the procedure of the test, including the inoculation of bacterial pathogens and the placement of antibiotic-impregnated disks on agar plates.