A novel method for determination of beta-lactamase using the agar dilution method

A novel test procedure is described for the rapid assay of beta-lactamase using the agar dilution method. The susceptibility to beta-lactamase was measured by adding an appropriate amount of enzyme to the diluting culture broth of a test organism in the agar dilution method. By this method, beta-lactamase susceptibility can be expressed in the same way as the MIC assay for antibiotics (microgram/ml). The results obtained with Escherichia coli beta-lactamase were closely related to the MIC patterns of the strains producing beta-lactamases.