Activity of clinafloxacin against multidrug-resistant Enterococcus faecium

Enterococci resistant to ampicillin, vancomycin, and/or aminoglycosides are a growing clinical problem. We studied the in vitro activity of the new fluoroquinolone clinafloxacin (PD 127,391) against 15 clinical isolates of multidrug-resistant Enterococcus faecium. In kill-kinetic studies, clinafloxacin (1 μg/ml) was bactericidal against 7 of 12 susceptible isolates, although substantial regrowth occurred in 4 isolates at 48 h. The addition of ampicillin (20 μg/ml) resulted in bactericidal activity in all 12 isolates, and no regrowth was seen. For three isolates resistant to clinafloxacin, effective killing was not observed at these concentrations of antibiotics. Clinafloxacin with ampicillin shows promising activity against many of these multiply resistant enterococci.