IN-VITRO ACTIVITY OF SPARFLOXACIN AND CLINAFLOXACIN AGAINST MULTIDRUG-RESISTANT ENTEROCOCCI

We evaluated the in vitro susceptibility of 140 clinical enterococcal isolates to the quinolones sparfloxacin and clinafloxacin. Isolates in cluded Enterococcus faecalis (107), Enterococcus faecium (29), Enteroc occus raffinosus (3), and one Enterococcus gallinarum. There were 111 isolates that showed high-level [minimum inhibitory concentrations (MI Cs) greater-than-or-equal-to 2000 mug/ml) resistance to gentamicin and were resistant to high levels of all other aminoglycosides; five isol ates produced beta-lactamase; 21 isolates were resistant (MIC greater- than-or-equal-to 16 mug/ml) to ampicillin and were not beta-lactamase producers; and 13 strains were resistant (MIC greater-than-or-equal-to 32 mug/ml) to vancomycin. Most strains were susceptible to low concen trations of sparfloxacin and clinafloxacin, with MIC90s of 0.6 mug/ml and 0.5 mug/ml, respectively. There were no inoculum effects. Time-kil l experiments were performed with 22 strains; using 2 x MIC at 24 h, a greater-than-or-equal-to 2 log10 reduction in growth was observed wit h sparfloxacin and clinafloxacin for 14 and 17 strains, respectively. Time-kill synergism experiments were performed with 15 strains lacking high-level aminoglycoside resistance. In vitro bacterial synergism wi th the combination of sparfloxacin or clinafloxacin with streptomycin or gentamicin was observed for five and 12 isolates, respectively. The bactericidal activity of sparfloxacin and clinafloxacin suggest that these antibiotics may prove useful for therapy of multidrug resistant enterococci.