Bactericidal properties of moxifloxacin and post-antibiotic effect

The time-kill kinetics and post-antibiotic effect (PAE) of moxifloxacin wer e studied for strains of Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, Staphylococcus aureus and Escherichia coli. Moxiflo xacin had a bactericidal effect against all strains tested, with the least rapid bactericidal effect being against S. pyogenes and the most rapid effe ct against S. aureus and E. coli. The PAE of moxifloxacin was similar to th at of other fluoroquinolones and increased with increasing concentration. N o association was found between the bactericidal effect of moxifloxacin and the duration of PAE. Gram-positive and Gram-negative organisms were also e xposed to concentrations of moxifloxacin, sparfloxacin and amoxycillin that simulated the drug concentrations obtained in human serum after standard o ral dosing schedules. Simulation of moxifloxacin concentrations in human se rum reduced viable counts more effectively and more rapidly than shown in t ime-kill experiments; in contrast, sparfloxacin and amoxycillin were less e ffective than when constant concentrations of these antibacterials were use d.