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 MIC(50) and MIC(90) were as follows: ciprofloxacin 4 and 64 microg/mL; clinafoxacin 0.5 and 4 microg/mL; levofloxacin 2 and 32 microg/mL; moxifloxacin 1 and 8 microg/mL; nalidixic acid 8 and 128 microg/mL; norfloxacin 64 and 256 microg/mL; sparfloxacin 1 and 16 microg/mL; and trovafloxacin 1 and 8 microg/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 microg/ml of reserpine, the MIC(90) 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.

Activity of clinafloxacin, compared with six other quinolones, against Acinetobacter baumannii clinical isolates.

The in vitro activity of clinafloxacin was studied in comparison with ciprofloxacin, levofloxacin, moxifloxacin, nalidixic acid, sparfloxacin and trovafloxacin against Acinetobacter baumannii clinical isolates. Clinafloxacin showed a MIC(90) of 4 mg/L, whereas the remaining quinolones showed a MIC(90) equal to or higher than 16 mg/L. MIC(50) determination in the presence of reserpine resulted in a two-fold decrease, except for trovafloxacin, which decreased four-fold, and for moxifloxacin and nalidixic acid, which did not change. The effect of reserpine was most pronounced among strains with a low level of resistance to quinolones. The MIC of clinafloxacin for strains with no mutation in either gyrA or parC genes ranged from 0.008 to 0.25 mg/L. In strains with a single mutation at amino acid codon Ser83 of the gyrA gene, the MIC of clinafloxacin ranged from 0.12 to 1 mg/L, whereas strains with a double mutation, one in the gyrA gene and another in the parC gene, showed a range of MIC of clinafloxacin from 1 to 8 mg/L. Therefore, clinafloxacin shows good activity against strains carrying a single mutation in the gyrA gene, and hence a second mutation is required for the microorganism to express resistance.