[Vancomycin-resistant enterococci: in vitro activity of quinupristin / dalfoprostin (RP 59500)]

The recent emergence of glycopeptide-resistant enterococci limits the treatment of enterococcal infections. The aim of this study was to evaluate the in vitro activity of a new streptogramin, quinupristin/dalfopristin, against 30 clinical isolates of vancomycin-resistant enterococci and compared with those of other 15 antimicrobials.

Enterococci were identified by using Rapid ID 32 Strep system. Genotyping of the isolates was performed by PCR. The MICs of quinupristin/dalfopristin were determined by the agar dilution technique recommended by the NCCLS. Susceptibilities to the rest of antibiotics tested (teicoplanin, ampicillin, penicillin, imipenem, doxycicline, chloramphenicol, gentamicin, streptomycin, rifampin, levofloxacin, fleroxacin, trovafloxacin, sparfloxacin, pefloxacin and clinafloxacin) were determined by using the E test. beta-lactamase production was examined with nitrocefin disks.

Quinupristin/dalfopristin has demonstrated excellent activity against Enterococcus faecium (MIC90' 2 micrograms/ml). Enterococcus faecalis was considerably less susceptible than E. faecium, at concentration of 4 micrograms/ml inhibited only 31% of tested strains. For doxycicline 77% of strains were susceptible. Only five isolates were susceptible to clinafloxacin; the other quinolones tested displayed poor activity. Resistance to chloramphenicol was detected in 47% of isolates. None of the isolates produced beta-lactamase.

This study indicates that vancomycin-resistant enterococci are often concomitantly resistant to multiple antibiotics. Quinupristin/dalfopristin was the most active agent tested against E. faecium strains. On the basis of these results quinupristin/dalfopristin could be a therapeutic option for the treatment of vancomycin-resistant E. faecium infections.