In vitro activity profile of oritavancin against resistant staphylococcal populations from a recent surveillance initiative in Europe

Abstract number: P539

Sahm D., Moeck G., Pillar C., Arhin F., Draghi D.

Objectives: Oritavancin (ORI), currently in clinical development for use in the treatment of infections caused by Gram-positive bacteria, is a potent bactericidal lipoglycopeptide. ORI has previously shown potent activity against staphylococci (STA), including resistant (R) strains. This surveillance (SUR) initiative was undertaken to profile the in vitro activity of ORI against drug-R and multi-drug resistant (MDR) STA in Europe (EU).

Methods: Recent (2005–2006) clinical isolates of S. aureus (SA; n = 557) and coagulase-negative staphylococci (CoNS; n = 78) from hospital sites in EU (48 sites; 15 countries), were centrally tested by broth microdilution (CLSI; M7-A7) against ORI and relevant comparators. ORI assays included 0.002% polysorbate-80 throughout. ORI activity was analysed for STA according to oxacillin (OX) susceptible (S) status and MDR phenotypes. MDR was defined as concurrent R to 3 of the following agents: ciprofloxacin (CIP), clindamycin (CLI), erythromycin (ERY), gentamicin (GEN), Ox, quinupristin-dalfopristin, trimethoprim-sulfamethoxazole (SXT), vancomycin, daptomycin (non-susceptible [NS]), and linezolid (NS).

Results: 58.9% of SA and 61.5% of CoNS had an MDR phenotype. The most prevalent MDR phenotypes among SA included 16.7% CIP-R, ERY-R, and OX-R; and 16% CIP-R, ERY-R, OX-R, and CLI-R. Among CNS, 24.4% were 6-drug R which included CIP, CLI, ERY, GEN, OX, and SXT.

Conclusions: SUR studies are essential for reviewing current trends in in vitro susceptibility patterns among antimicrobial agents used to treat serious infections. ORI had potent and consistent activity against a diverse EU collection of staphylococci which included OX-R and MDR phenotypes.