Oritavancin activity against vancomycin-susceptible and vancomycin-resistant Enterococci with molecularly characterized glycopeptide resistance genes recovered from bacteremic patients, 2009-2010.

Oritavancin exhibited potent activity against vancomycin-susceptible (MIC(50) and MIC(90), 0.015/0.03 μg/ml) and vanB-carrying E. faecalis isolates (MIC(50) and MIC(90), 0.015 and 0.015 μg/ml). Higher (16- to 32-fold) MIC(50)s and MIC(90)s for vanA-harboring E. faecalis were noted (MIC(50) and MIC(90), 0.25 and 0.5 μg/ml), although oritavancin inhibited all strains at ≤ 0.5 μg/ml. Vancomycin-susceptible and vanB-carrying E. faecium strains (MIC(50) and MIC(90), ≤ 0.008 and ≤ 0.008 μg/ml for both) were very susceptible to oritavancin, as were VanA-producing isolates (MIC(50) and MIC(90), 0.03 and 0.06 μg/ml). Oritavancin exhibited good in vitro potency against this collection of organisms, including vancomycin-resistant enterococci.