Ertapenem (MK-0826), a new carbapenem: comparative in vitro activity against clinically significant anaerobes.

Abstract Ertapenem, a new long acting β-lactam with broad-spectrum antimicrobial coverage, was tested in vitro to compare its activity against 556 clinical isolates of anaerobes to other established agents using a broth microdilution method as recommended by the NCCLS. Against all anaerobes ertapenem inhibited 99.1% of isolates at 4 μg/mL, had a mode MIC of 0.12 μg/mL, and showed activity comparable to imipenem, meropenem, trovafloxacin, piperacillin-tazobactam, and metronidazole. Five of the B. fragilis group (4 B. fragilis , 1 B. vulgatus ) isolates tested showed reduced susceptibility (≥8 μg/mL; Prevotella, Porphyromonas, Fusobacterium , and Peptostreptococcus were susceptible. Only piperacillin-tazobactam had susceptible MIC’s for all test isolates followed by metronidazole and the carbapenems exhibiting low resistance rates (