In vitro activity of clinafloxacin in comparison with other quinolones against Stenotrophomonas maltophilia clinical isolates in the presence and absence of reserpine

A total of 33 Stenotrophomonas maltophilia clinical isolates were tested for their susceptibility to clinafloxacin in comparison with ciprofloxacin, levofloxacin, moxifloxacin, nalidixic acid, norfloxacin, sparfloxacin and trovafloxacin. The MIC₅₀ and MIC₉₀ were as follows: ciprofloxacin 4 and 64 μg/mL; clinafoxacin 0.5 and 4 μg/mL; levofloxacin 2 and 32 μg/mL; moxifloxacin 1 and 8 μg/mL; nalidixic acid 8 and 128 μg/mL; norfloxacin 64 and 256 μg/mL; sparfloxacin 1 and 16 μg/mL; and trovafloxacin 1 and 8 μg/mL. Clinafloxacin was the most active quinolone, with only a 15.1% of strains showing resistance. When the MICs were determined in the presence of 25 μg/ml of reserpine, the MIC₉₀ of trovafloxacin and moxifloxacin did not change, whereas decreased 2-fold for clinafloxacin, levofloxacin, sparfloxacin and nalidixic acid, and 4- and 8-fold for ciprofloxacin and norfloxacin respectively. No clinafloxacin-resistant strains were observed when the MIC was performed in the presence of reserpine. Therefore, clinafloxacin shows the better "in vitro"activity against these 33 strains of S.maltophilia.