Susceptibility of moxalactam to beta-lactamase.

Moxalactam is not significantly susceptible to the majority of beta-lactamases produced by bacteria of clinical relevance. However, two types of enzyme--PSE2 and PSE3--from Pseudomonas aeruginosa can hydrolyze this antibiotic at a significant rate. In this respect moxalactam is similar to 7-alpha-methoxy cephem compounds, such as cefoxitin, which are also susceptible to these enzymes. Moxalactam, like other beta-lactam antibiotics having an acid function in the side chain, is a potent inhibitor of the cephalosporinase from Enterobacter cloacae (type Ia beta-lactamase).