In Vitro and in Vivo Activities of the Novel Ketolide RBx 14255 Against Clostridium Difficile.

ABSTRACT The MIC 90 of RBx 14255, a novel ketolide, against Clostridium difficile was 4 μg/ml (MIC range, 0.125 to 8 μg/ml), and this drug was found to be more potent than comparator drugs. An in vitro time-kill kinetics study of RBx 14255 showed time-dependent bacterial killing for C. difficile . Furthermore, in the hamster model of C. difficile infection, RBx 14255 demonstrated greater efficacy than metronidazole and vancomycin, making it a promising candidate for C. difficile treatment.