Comparative antistreptococcal activity of two newer fluoroquinolones, levofloxacin and sparfloxacin.

The objective of this study was to evaluate the in vitro activity of sparfloxacin, levofloxacin, ofloxacin, and ciprofloxacin against contemporary strains of streptococci. Susceptibility testing of a panel of 300 recent clinical isolates of streptococci (100 each of beta-hemolytic, viridans group, and Streptococcus pneumoniae) using reference broth microdilution methods was performed, and the results were compared. Sparfloxacin was the most active of the four tested fluoroquinolones, inhibiting 99-100% of all isolates at concentrations of < or = 1 microgram/ml, and was two- to eightfold more potent than the three comparative agents. Levofloxacin was also quite active, inhibiting 98-100% of the isolates at concentrations < or = 2 micrograms/ml. Both sparfloxacin and levofloxacin possess an improved spectrum and potency against contemporary strains of streptococci compared to currently available fluoroquinolones.