Antimicrobial activity of moxifloxacin, gatifloxacin and six fluoroquinolones against Streptococcus pneumoniae.

The in vitro and pharmacodynamic effects of moxifloxacin and gatifloxacin against Streptococcus pneumoniae were compared with six other fluoroquinolones. Organisms included penicillin-susceptible (54) and penicillin-non-susceptible (145) isolates from 1998-1999. Moxifloxacin and clinafloxacin demonstrated the greatest in vitro activity, with MIC90s of 0.13 mg/L, followed by trovafloxacin, grepafloxacin > gatifloxacin, sparfloxacin > levofloxacin > ciprofloxacin. There was no difference in fluoroquinolone activity between penicillin-susceptible and -non-susceptible strains. Pharmacodynamic analysis using published pharmacokinetic information indicates that all the agents tested except ciprofloxacin had an AUC/MIC90 > 30, with moxifloxacin having the greatest free-drug availability.