Affinity of Tomopenem (CS-023) for Penicillin-Binding Proteins in Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa

Tomopenem (formerly CS-023), a novel 1β-methylcarbapenem, exhibited high affinity for penicillin-binding protein (PBP) 2 in Staphylococcus aureus, PBP 2 in Escherichia coli, and PBPs 2 and 3 in Pseudomonas aeruginosa, which are considered major lethal targets. Morphologically, tomopenem induced spherical forms in E. coli and short filamentation with bulges in P. aeruginosa, which correlated with the drug's PBP profiles. The potential of resistance of these bacteria to tomopenem was comparable to that to imipenem.