[Comparative study of the bacteriostatic and bactericidal activity of levofloxacin against Pasteurella strains...

The MICs of seven quinolones, nalidixic acid, pefloxacin, ofloxacin, d-ofloxacin, ciprofloxacin, sparfloxacin and levofloxacin, were determined by agar dilution method comparatively to those of amoxycillin, cefpodoxime, doxycyclin and clarithromycin against 75 clinical isolates of Pasteurella multocida, P. dagmatis and P. canis. Time-kill method was performed for three selected P. multocida isolates. Fluoroquinolones were the most active agents. At concentration of 0.016 mg/L of sparfloxacin or levofloxacin the 75 isolates were inhibited. The MICs of levofloxacin and sparfloxacin showed that the activity of these molecules was two to four times higher than that of the other quinolones studied. Time-kill studies showed a complete killing in six hours with the CMI x 2 of pefloxacin, ofloxacin, ciprofloxacin, sparfloxacin and levofloxacin. This result was obtained more rapidly with the quinolones than with amoxicillin or cefpodoxime. Doxycycline and clarithromycin were devoid of bactericidal activity.