SUSCEPTIBILITY OF CIPROFLOXACIN-RESISTANT STAPHYLOCOCCI AND ENTEROCOCCI TO TROVAFLOXACIN

The susceptibilities of clinical isolates of methicillin-resistant Sta phylococcus aureus (MRSA) and enterococci obtained over a 13-year peri od were tested for trovafloxacin, a new fluoroquinolone, and ciproflox acin. For MRSA, MIG(50) values for trovafloxacin increased from 0.03 m u g/ml to 1 mu g/ml from 1984-1985 to 1995-1996, but were lower than t hose noted for ciprofloxacin, which increased from 0.25 mu g/ml to >8 mu g/ml during the same period. Trovafloxacin also showed lower MIC(50 ) values (0.12-0.25 mu g/ml) than ciprofloxacin (MIC(50) of 0.5-1 mu g /ml) for E. faecalis isolates from 1985 through 1991, but against E. f aecium and E. faecalis isolated in 1995-1996, the MIC(50) values for b oth trovafloxacin and ciprofloxacin were 2 mu g/ml and the MIC(90) val ues were greater than or equal to 8 mu g/ml. Thus, cross-resistance be tween fluoroquinolones was shown for both enterococci and MRSA. Whethe r the greater intrinsic activity of trovafloxacin might allow its use in treating MRSA and enterococcal infections remains to be seen. (C) 1 996 Elsevier Science Inc.