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 (MIC₉₀, 4 and 2 μg/ml, respectively) and only a single strain presented intermediate susceptibility to tigecycline (MIC₉₀, 0.25 μg/ml). Thirty percent of strains were resistant to Q-D (MIC₉₀, 4 μg/ml), and CFT was constantly inactive (MIC₉₀, 64 μg/ml). Finally, TLV showed low-level MICs (MIC₉₀, 0.5 μg/ml) against vanB-positive isolates but not against vanA-positive isolates (MIC₉₀, 8 μg/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).