Synergy testing of vancomycin-resistant Enterococcus faecium against quinupristin-dalfopristin in combination with other antimicrobial agents

Abstract

Using checkerboard and time-kill assays, we evaluated the in vitro activity of quinupristin-dalfopristin (RP 59500) alone and in combination with five other antimicrobial agents against 12 clinical strains of vancomycin-resistant Enterococcus faecium (VREF). In time-kill studies, six VREF strains exhibited synergism with the combination of quinupristin- dalfopristin and doxycycline and three exhibited synergism with quinupristin- dalfopristin plus ampicillin-sulbactam. Combinations of quinupristin- dalfopristin with these and other agents warrant further clinical evaluation for the treatment of serious VREF infections.