Surotomycin Demonstrates Low In Vitro Frequency of Resistance and Rapid Bactericidal Activity in Clostridium difficile, Enterococcus faecalis, and Enterococcus faecium

Surotomycin (CB-183,315) is an orally administered, minimally absorbed, selective bactericidal cyclic lipopeptide in phase 3 development for the treatment of Clostridium difficile-associated diarrhea. The aim of this study was to evaluate the emergence of resistance in C. difficile (ATCC 700057 and three recent clinical isolates from the restriction endonuclease analysis groups BI, BK, and K), vancomycin-susceptible (VS) Enterococcus faecalis (ATCC 49452), vancomycin-resistant (VR) E. faecalis (ATCC 700802), VS Enterococcus faecium (ATCC 6569), and VR E. faecium (ATCC 51559) under anaerobic conditions. The rate of spontaneous resistance was below the limit of detection (