In Vitro Activities of CB-183,315, Vancomycin, and Metronidazole against 556 Strains of Clostridium difficile, 445 Other Intestinal Anaerobes, and 56 Enterobacteriaceae Species

MICs of CB-183,315, a novel lipopeptide antibiotic, vancomycin, and metronidazole were determined for intestinal anaerobes and Enterobacteriaceae. The MIC(90)s for Gram-negative anaerobes were > 8,192, 8,192, and 4 mu g/ml for CB-183,315, vancomycin, and metronidazole, respectively. Against Enterobacteriaceae, the MIC(90)s were > 8,192 mu g/ml, 1,024 mu g/ml, and 1,024 mu g/ml, respectively. The CB-183,315 MIC90 for Clostridium difficile was 0.5 mu g/ml. Its lack of activity against normal fecal organisms makes it a promising new agent for treating C. difficile.