In vitro activities of parenteral beta-lactam antimicrobials against TEM-10-, TEM-26- and SHV-5-derived extended-spectrum beta-lactamases expressed in an isogenic Escherichia coli host

The in vitro activities were determined and time-kill studies of cefepime, imipenem-cilastatin, meropenem and piperacillin-tazobactam were performed a gainst SHV- and TEM-derived extended-spectrum beta-lactamases (ESBLs). Sequ ence-confirmed SHV-5, TEM-10 and TEM-26 beta-lactamases were transferred in to Escherichia coli C600N by conjugation. Imipenem and meropenem were more active (MIC range 0.0625-0.25 mg/L) than cefepime (MIC range 2-8 mg/L) and piperacillin-tazobactam (MIC range 8-32 mg/L). Regrowth of strains expressi ng TEM-10 and TEM-26 was noted at all cefepime and piperacillin-tazobactam concentrations studied. Imipenem-cilastatin and meropenem demonstrated rapi d, sustained bactericidal activity uninfluenced by the type of ESBL express ed.