A Novel Method for Determination of β-Lactamase Using the Agar Dilution Method

A novel test procedure is described for the rapid assay of β-Lactamase using the agar dilution method. The susceptibility to β-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, β-Lactamase susceptibility can be expressed in the same way as the MIC assay for antibiotics (µg/ml). The results obtained with Escherichia coli β-Lactamase were closely related to the MIC patterns of the strains producing β-Lactamases.