New sensitive bioassay for sulbactam in bovine tissues.

A quantitative cylinder plate bioassay for sulbactam has been developed which can detect concentrations as low as 0.01 microgram/g in bovine muscle, fat, kidney, and liver tissues. This procedure may also be applicable to human tissues and fluids. In addition to the improved sensitivity, this method differs from all previously described systems because it is based on inhibition by sulbactam of a cell-free beta-lactamase incorporated in the assay agar. The assay is unaffected by the presence of ampicillin even at concentrations 10 times that of the sulbactam concentration. This report describes the analytical technique as well as the accuracy and precision of the method. The assay can be applied to tissue depletion studies.