STREPTOCOCCUS-PNEUMONIAE KILLING RATE AND POSTANTIBIOTIC EFFECT OF LEVOFLOXACIN AND CIPROFLOXACIN

In vitro killing rates for levofloxacin and ciprofloxacin for six stra ins of Streptococcus pneumoniae were determined by the time-kill metho d outlined by the NCCLS. Both drugs were bactericidal at concentration s of two and four times their respective minimum inhibitory concentrat ions (MICs). Levofloxacin achieved a 99.9% kill on average in 1 hour m ore rapidly than ciprofloxacin. Post-antibiotic effect was also determ ined for both drugs against the same six strains. A post-antibiotic ef fect for a mean of 1.2 and 1.0 hours was observed for levofloxacin and ciprofloxacin, respectively. The latter means were not considered sig nificantly different.