Activity of oritavancin against gram-positive clinical isolates responsible for documented skin and soft-tissue infections in european and us hospitals (2010-13)

Abstract

Objectives: To assess oritavancin activity in vitro against clinically relevant Gram-positive pathogens causing skin and soft-tissue infections (SSTIs) in European and US hospitals. Methods: 13262 consecutive and unique isolates deemed to be responsible for SSTIs were included. Isolates originated from 36 and 27 institutions in Europe (Israel included) and the USA, respectively, between 2010 and 2013. Results: Oritavancin (98.8% susceptible) showed modal MIC, MIC50 and MIC90 results of 0.03, 0.03 and 0.06 mg/L, respectively, for Staphylococcus aureus. CoNS from the USA (MIC50, 0.015 mg/L) demonstrated an MIC50 value of oritavancin slightly lower than those from Europe (MIC50, 0.03 mg/L). Overall, vancomycin-resistant (VanA-phenotype) Enterococcus faecalis had oritavancin MICs (MIC50/90, 0.25/0.5 mg/L) that were 16-fold higher than those obtained for vancomycin-susceptible isolates (MIC50/90, 0.015/0.03 mg/L; 99.2%-99.8% susceptible); nevertheless, oritavancin inhibited all VanA E. faecalis at ≤0.5 mg/L. Equivalent oritavancin MICs (MIC50/90, 0.004/0.008 mg/L) were noted for all VanB and vancomycin-susceptible Enterococcus faecium, while higher MICs (MIC50/90, 0.03/0.12 mg/L) were obtained for VanA strains. Oritavancin had low MICs against the overall populations of Streptococcus pyogenes (MIC50/90, 0.03/0.12 mg/L; 98.4%-98.6% susceptible), Streptococcus agalactiae (MIC50/90, 0.03/0.06 mg/L; 97.9%-98.0% susceptible) and the Streptococcus anginosus group (MIC50/90, 0.008/0.015 mg/L; 100.0% susceptible), with slightly higher MICs for Streptococcus dysgalactiae (MIC50/90, 0.06/0.25 mg/L; ≤98.3% susceptible). Conclusions: Oritavancin had potent activity in vitro against this contemporary collection of European and US isolates causing SSTIs. These results describe oritavancin activity against Gram-positive pathogens collected shortly prior to its regulatory approval in the USA.