Inactivation of Staphylococcal Penicillinase by Reaction with Resistant Penicillins

Abstract

WHILE studying the kinetics of penicillinase inactivation of various penicillins, it became evident that a penicillinase-susceptible penicillin, such as benzyl-penicillin, behaved differently from resistant penicillins, such as methicillin (2,6-dimethoxyphenyl penicillin) or oxaoillin (5-methyl-3-phenyl-4-isoxazolyl penicillin). (The trade name of Bristol Laboratories, Division of Bristol Myers Co., for methicillin is ‘Staphcillin’ and for oxacillin is ‘Prostaphlin’,) The former was decomposed at a constant rate for the greater part of the reaction while the rate of decomposition of the resistant penicillins progressively decreased and only a small fraction of the penicillin was finally destroyed under the conditions of this experiment.