Effect of porins and plasmid-mediated AmpC beta-lactamases on the efficacy of beta-lactams in rat pneumonia caused by Klebsiella pneumoniae.

The in vivo activities of imipenem, meropenem, and cefepime were studied in a model of rat pneumonia caused by a plasmid-mediated AmpC beta-lactamase ACT-1-producing Klebsiella pneumoniae strain (K. pneumoniae strain 12) and a derivative porin-deficient mutant (K. pneumoniae strain 12dp). No differences between these activities were seen with K. pneumoniae 12. Only meropenem showed an activity slightly better than that of imipenem with K. pneumoniae 12dp.