Rapid method for determining the beta-lactamase-inducing potency of drugs.

A rapid semiquantitative method for determining the beta-lactamase inducing potency of drugs was developed. Bacteria carrying a gene for inducible beta-lactamase expression were inoculated at a concentration of 10(8) CFU/ml into microtiter plates for determination of MICs, which were recorded after 4 h of incubation. A suitable chromogenic beta-lactamase substrate was then added, and after incubation for another 3 h colour changes were monitored.