Measurement of levels of aminoglycosides and vancomycin in serum in the presence of new beta-lactam antibiotics.

We evaluated the effect of new beta-lactam antibiotics (azlocillin, mezlocillin, piperacillin, cefotaxime, moxalactam, and cefoperazone) on assays for aminoglycosides and vancomycin. These antibiotics produced no interference in an immunoassay for gentamicin and tobramycin. The new penicillins produced no interference in a bioassay of amikacin and vancomycin with penicillinase incorporated into the assay agar. Bioassay in the presence of the cephalosporins required predigestion with cephalosporinase. We describe a method for accurate bioassay in the presence of the available cephalosporins, with the exception of moxalactam.