In vitro activity of new antimicrobial agents against glycopeptide-resistant Enterococcus faecium clinical isolates from France between 2006 and 2008.

Objective: The aim of this study was to determine the in vitro activity of six new antimicrobial agents against glycopeptide-resistant enterococci (GRE) strains from France.

Methods: Sixty epidemiologically unrelated clinical isolates of Enterococcus faecium (vanA or vanB), received at the National Reference Centre for Enterococci (CNR-Enc) between 2006 and 2008, were studied. The MICs of the following antibiotics were determined by broth microdilution according to Antibiogram Committee of the French Society for Microbiology (CA-SFM) guidelines: quinupristin-dalfopristin (Q-D), linezolid (LZD), daptomycin (DPT), tigecycline (TGC), ceftobiprole (CFT), and telavancin (TLV). Strains were classified using clinical breakpoints recommended by the CA-SFM (Q-D, LZD, TGC), or the Clinical and Laboratory Standards Institute (DPT).

Results: All strains were susceptible to LZD and DPT (MIC(90), 4 and 2μg/ml, respectively) and only a single strain presented intermediate susceptibility to tigecycline (MIC(90), 0.25μg/ml). Thirty percent of strains were resistant to Q-D (MIC(90), 4μg/ml), and CFT was constantly inactive (MIC(90), 64μg/ml). Finally, TLV showed low-level MICs (MIC(90), 0.5μg/ml) against vanB-positive isolates but not against vanA-positive isolates (MIC(90), 8μg/ml).

Conclusion: Although several antibiotics are still active against GRE, it is essential to maintain an active antimicrobial resistance surveillance for these microorganisms considered as a model of multidrug resistance with a potential to transfer resistance to other bacterial species (e.g. Staphylococcus aureus).