32. Describe the Kirby-Bauer method of antibiotic susceptibility testing.
33. Describe how the results of the Kirby-Bauer procedure are interpreted.
34. Describe the use of broth dilution tests.
These tests are used to determine which chemotherapeutic agent is most likely to combat a specific pathogen.
These tests are used when susceptibility cannot be predicted or when drug resistance arises.
In this test, also known as the Kirby-Bauer test, a bacterial culture is inoculated on an agar medium, and filter paper disks impregnated with chemotherapeutic agents are overlaid on the culture.
After incubation, the absence of microbial growth around a disk is called a zone of inhibition.
The diameter of the zone of inhibition, when compared with a standardized reference table, is used to determine whether the organism is sensitive, intermediate, or resistant to the drug.
MIC is the lowest concentration of drug capable of preventing microbial growth; MIC can be estimated using the E test.
A plastic coated strip contains a gradient of antibiotic concentrations and the minimal inhibitory concentration is read from a scale printed on the strip.
In a broth dilution test, the microorganism is grown in a liquid media containing different concentrations of a chemotherapeutic agent.
The lowest concentration of a chemotherapeutic agent that kills bacteria is called the minimum bactericidal concentration (MBC).