Use of high performance liquid chromatography for increased assay sensitivity of beta-lactamase activity in bile

A study to develop a sensitive method for measuring beta-lactamase activity in bile was conducted. Since separation of substrate from biological components is required to increase the assay sensitivity and to achieve an accurate assay of beta-lactamase activity, high performance liquid chromatography (HPLC) was used for separation and analysis of the substrates (cephaloridine for cephalosporinase, benzylpenicillin for penicillinase and cefuloxime for cefuloximase). In addition, conditions for increased assay sensitivity were also studied and optimal substrate concentrations and reaction times were determined. beta-Lactamase activity of 0.05 munit/ml in bile was detected using the HPLC assay method which is a significant improvement when compared to the direct spectrophotometric method which has a detection limit of approximately 10 munit/ml.