In vitro and in vivo activities of the novel Ketolide RBx 14255 against Clostridium difficile.

The MIC90 of RBx 14255, a novel ketolide, against Clostridium difficile was 4 mu g/ml (MIC range, 0.125 to 8 mu g/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.