In vitro antimicrobial activity of grepafloxacin and its therapeutic efficacy on respiratory infections

We carried out laboratory and clinical studies on grepafloxacin (GPFX), a new oral pyridone carboxylic acid, antimicrobial drug. 1) Laboratory activity The minimum inhibitory concentrations (MICs) of GPFX for a total of 334 clinically isolated strains and 40 standard strains were determined and compared with those of tosufloxacin (TFLX), ofloxacin (0FLX), ciprofloxacin (CPFX), enoxacin (ENX), norfloxacin (NFLX), sparfloxacin (SPFX) and erythromycin (EM). GPFX proved to have a broad antibacterial spectrum, and its in vitro activity against gram-positive cocci was the same as that of TFLX, and more potent than that of the other five reference quinolones. Against gram-negative bacilli except Legionella pneumophila, the in vitro activity of GPFX was the same or lower than that of TFLX, and more potent than that of the other drugs. The MIC₉₀ of GPFX for clinical isolates of L. pneumophila was almost equal to that of SPFX, and superior to those of the other drugs. The MIC₉₀ of GPFX for standard strains of Legionella spp. was slightly inferior to those of TFLX and SPFX, and the same as that of CPFX. 2) Clinical efficacy We administered GPFX to five patients with respiratory tract infection at a dose of 200~300 mg daily for 7 to 14 days. The clinical results were good in 5 cases, yielding an efficacy rate of 100%. In all cases, neither side effects nor abnormal laboratory findings were observed.