Bactericidal activity of telavancin, vancomycin and metronidazole against Clostridium difficile.

We compared the time-kill activities of telavancin, vancomycin and metronidazole at concentrations of 2 times, 4 times, and 8 times their respective MICs against five Clostridium difficile strains including REA type BI, using inocula that contained predominantly either vegetative cells or spores. Telavancin MICs (0.125-0.25 microg/ml) were 2-8-fold lower than those of vancomycin. Telavancin was bacteriostatic, reducing the inoculum by 1-2.5 log(10) after 24 h. No major differences occurred with the different inoculum forms or the REA types. Although telavancin MICs were 2-8 times lower than vancomycin, both demonstrated similar bacteriostatic activity against C. difficile while metronidazole was bactericidal.