Moxalactam: an oxa-beta-lactam antibiotic that inactivates beta-lactamases.

Moxalactam, like cefoxitin, cefuroxime, and cefotaxime, shows little or no interaction with penicillinases. Resistance of moxalactam to cephalosporinases, however, appears to be considerably greater than that of these other recently discovered beta-lactam antibiotics. Moxalactam is a beta-lactamase inactivator and inactivates most of the cephalosporinases produced by gram-negative bacteria. The process of inactivation is specific and follows time-dependent or progressive kinetics, as is the case for a class of enzyme inhibitors called "suicide substrates." Moxalactam is the first beta-lactam antibiotic shown to possess this property of inactivation of beta-lactamases, a property that explains its excellent resistance to beta-lactamases.