The bactericidal activity of levofloxacin against ampicillin-resistant and ampicillin-susceptible Haemophilus influenzae in comparison with ofloxacin, ciprofloxacin and sparfloxacin

The bactericidal activity of levofloxacin against four Haemophilus influenzae clinical isolates (two ampicillin-resistant and two susceptible) was compared with that of ofloxacin, ciprofloxacin and sparfloxacin at concentrations simulating the peak serum concentrations obtained with the recommended oral doses. Bactericidal activity was assessed using time-kill curves and minimum kill-time values. Both concentrations of levofloxacin rapidly killed all the study strains, with mean kill times of 4 h and no viable bacteria remaining after 18-h exposure. The bactericidal activities of levofloxacin, ofloxacin and sparfloxacin were similar. The minimum kill-times for both concentrations of ciprofloxacin were 28-35% longer than those of levofloxacin. These results support the use of levofloxacin for H. influenzae infections, including ampicillin-resistant strains.