5 Questions
What is the purpose of the Kirby-Bauer disk diffusion test?
To test the susceptibility of microbes to antimicrobial drugs
What is placed on the agar plate during the Kirby-Bauer assay?
Filter paper disks impregnated with antibiotics
How is antibacterial activity observed in the Kirby-Bauer disk diffusion test?
By noting the presence of a clear circular zone of inhibition
Why does the interpretation of the Kirby-Bauer assay provide only limited information on susceptibility and resistance?
Lack of standardization in factors affecting zone sizes
Why can differences in zone sizes not be used to compare drug potencies or efficacies in the Kirby-Bauer test?
The assay cannot distinguish between bacteriostatic and bactericidal activities
Study Notes
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.
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