Question

39 >>> Question 36 3.3333 points Save Answer Which statement among A-D is false regarding the Kirby-Bauer method for antibiotic sensitivity testing? A. The size of the zone of inhibition surrounding the antibiotic disk is measured by the diameter across that zone. B. The bacterial strain to be tested must first be streaked on the plate with a wire loop via the quadrant method in order to obtain isolated colonies. C. The formation of a zone of inhibition around an antibiotic disk does not necessarily indicate that the bacterial strain is susceptible to the antibiotic. D. Antibiotic in the disk diffuses into the agar, both laterally and downward into the agar. E. None of A-D is false.

Answer 1

Answer. B

Kirby Bauer method is used to assess minimum inhibitory concentration of an antibiotic. Small disks soaked in antibiotics are placed on a lawn of bacterial cells in an agar plate and kept for incubation. One can observe zone of clearance around the disk.
These are areas of killed bacteria due to the affect of the antibiotic. the diameter of the zone of clearance is measured.

The larger the diameter of the zone of clearance, the more sensitive the bacteria are to a particular concentration of the antibiotic.

The disks soaked in antibiotic allow the antibiotic to diffuse into the agar. We preapare a lawn of bacterial cells on the agar plate. If not then one may falsely interpret the clear agar surface (where bacteria were not spread) for the action of antibiotic.