Antibacterial activity of meropenem against gram-negative bacteria with a permeability defect and against staphylococci.

Meropenem, like imipenem, showed a good affinity for high molecular weight PBPs of Escherichia coli and Pseudomonas aeruginosa and had a better affinity for PBP3 than imipenem. Meropenem, like imipenem, also remained almost fully active against permeability mutants of enterobacteria lacking in confirmed or putative porins. This good permeation of the carbapenems may relate to their zwitterionic character. In-vitro, mutants and clinical isolates of P. aeruginosa, for which the MIC of imipenem was greater than or equal to 4 mg/l, were always more sensitive to meropenem. Methicillin resistant staphylococci were sensitive neither to imipenem nor to meropenem.