SUSCEPTIBILITY OF CIPROFLOXACIN-RESISTANT STAPHYLOCOCCI AND ENTEROCOCCI TO CLINAFLOXACIN

Clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA ) and Enterococcus faecalis obtained from the Ann Arbor Veterans Affai rs Medical Center within the last decade were tested for susceptibilit y to ciprofloxacin and clinafloxacin. For MRSA isolates, the minimum i nhibitory concentrations (MICs) of ciprofloxacin were several fold hig her than those noted with clinafloxacin. Prior to the introduction of the fluoroquinolones (1984-1985), all MRSA isolates were susceptible t o ciprofloxacin and clinafloxacin. By 1993, virtually all MRSA isolate s were resistant to ciprofloxacin and a 50-fold increase in the MIC(50 ) and MIC(90) for clinafloxacin was seen. In 1985-1986, most enterococ cal isolates were susceptible to ciprofloxacin and clinafloxacin. By 1 993, one-third of all enterococci were resistant to both ciprofloxacin and clinafloxacin. Fluoroquinolone resistance developed more quickly in enterococci that demonstrated high-level gentamicin resistance. Thu s, cross-resistance between clinafloxacin and ciprofloxacin was seen; however, the lower MICs of clinafloxacin for MRSA may allow the use of this drug for some MRSA infections.