Influence of dose frequency on the therapeutic efficacies of ciprofloxacin and ceftazidime in experimental Klebsiella pneumoniae pneumonia and septicemia in relation to their bactericidal activities in vitro.

The antibacterial activities of ciprofloxacin versus ceftazidime against Klebsiella pneumoniae in vitro and in vivo were compared. Although there was only a minor difference in MBC values between both drugs ciprofloxacin demonstrated a high and dose-dependent bacterial killing rate in vitro and in lungs of leukopenic rats in contrast to the more time-dependent bactericidal activity of ceftazidime. After treatment of a K.pneumoniae pneumonia and septicemia the efficacy of ciprofloxacin was only slightly influenced by the mode of administration, either at 6-h intervals or continuously, whereas ceftazidime was far more effective after continuous administration. This resulted in a superior efficacy of ciprofloxacin after intermittent treatment as compared to ceftazidime, whereas ceftazidime was more effective after continuous administration as compared to ciprofloxacin. Also ciprofloxacin proved to be bactericidal against bacteria that were not actively growing, both in vitro and in vivo, whereas ceftazidime was not.