Question

If you perform a kirby baker assay and there is a zone of inhibition present after incubation, does that necessarily mean the bacteria is susceptible to the antibiotic? why or why not? Discuss the role of standardized interpretive charts.

Answer 1

The formation of zone of inhibition depends on many factor like solubility of the antibiotic, rate of its diffusion on agar, thickness of the agar media on plate, the drug conc. etc.

If in a well spreaded plate if the bacteria is visible in whole plate except the region around the antibiotic disc, that clearly indicates zone of inhibition formation. The larger the area, greater is the effectiveness of antibiotic. Thicker the agra on plate, higher would be the downward movement of antibiotic hence resulting in smaller zones of inhibition.

Standardized charts can help in interpretation of laboratoty results as these are based on previously conducted experiments.