Antibacterial activity of T-5575, a novel 2-carboxypenam, and its stability to beta-lactamase

The in-vitro activity of T-5575, 2-carboxypenam, a new parenteral antibiotic and its stability to beta-lactamases were compared with those of ceftazidime and imipenem. The activity of T-5575 was equal or superior to that of ceftazidime or imipenem against Gram-negative bacteria that produced penicillinase with the exception of the enzyme OXA-1. Against strains that produced cephalosporinase and zinc-dependent beta-lactamase, the activity of T-5575 was superior to that of ceftazidime or imipenem. T-5575 was a poor substrate and had low affinity for beta-lactamases produced by Citrobacter freundii, Enterobacter cloacae and Pseudomonas aeruginosa. The activity of T-5575 was less influenced by the derepressed production of chromosomal enzymes than that of ceftazidime. Overall, T-5575 had excellent activity against Gram-negative pathogens that produced various types of beta-lactamases.