Use of Etests with carbapenems for Gram-negative rods producing beta-lactamases.

The in vitro activity of imipenem and meropenem on strains of Gram-negative rods producing extended-spectrum beta-lactamase (ESBL) and inducible beta-lactamase (IBL) was studied using the Etest. In all, 185 strains from the surgical intensive care units of four different hospitals were looked at over 2 years. Of these, 94 were ESBL producers and 91 were IBL positive. The in vitro sensitivities of imipenem and meropenem were 89.7 and 95.1%, respectively, against all strains. The imipenem and meropenem sensitivities of Klebsiella spp. were 98.4 and 100%, respectively, but imipenem resistance (21.6%) in Pseudomonas aeruginosa strains was higher than that of meropenem (10.8%).