Relative inactivation by Staphylococcus aureus of eight cephalosporin antibiotics

These studies extend the recent observation that cefazolin is inactivated to a greater extent than cephaloridine by some strains of penicillinase-producing Staphylococcus aureus, whereas cephalothin undergoes little if any inactivation. In Mueller-Hinton broth (inoculum, 3 x 10(6)) 100 recently isolated strains had minimal inhibitory concentrations (MICs) 2 mug/ml and 10% (designated "resistant" strains) were >8 mug/ml for cephaloridine but remained