beta-lactamase stability of HR 756, a novel cephalosporin, compared to that of cefuroxime and cefoxitin.

The stability to beta-lactamase hydrolysis of HR 756, a new cephalosporin antibiotic, was compared to the beta-lactamase stability of cefoxitin and cefuroxime. HR 756, cefoxitin, and cefuroxime were not hydrolyzed by Richmond type I, III, IV, and V beta-lactamases. Antibacterial activity of HR 756 correlated well with resistance to beta-lactamase hydrolysis except against Pseudomonas aeruginosa. HR 756, cefoxitin, and cefuroxime inhibited type I beta-lactamases, but not type III, IV, or V enzymes. HR 756 was the most active inhibitor.