In vitro antimicrobial activity of balofloxacin and its therapeutic efficacy in respiratory infections

We performed measured laboratory and clinical studies on balofloxacin (BLFX), a new oral pyridone-carboxylic acid derivative. 1) Laboratory activity. The minimum inhibitory concentrations (MICs) of BLFX for a total of 397 strains clinically isolated and 41 standard strains of Legionella spp. were determined and compared with those of tosufloxacin (TFLX), ofloxacin (OFLX), ciprofloxacin (CPFX), and sparfloxacin (SPFX). BLFX proved to have a broad antibacterial spectrum, and its in vitro activity against gram-positive cocci, especially MRSA, was more potent than that of the other four reference quinolones. Against gram-negative bacilli, the in vitro activity of BLFX was the same or slightly lower than that of the other drugs. 2) Clinical efficacy. We administered BLFX to ten patients with respiratory tract infections (bronchopneumonia: 3 cases, acute exacerbation of COPD: 4 cases, acute exacerbation of bronchiectasis: 1 case, mycoplasmal pneumonia: 2 cases) at a dose of 200~400 mg daily for 7 to 14 days. The clinical efficacy was excellent in 3 cases and good in 7. Causative bacteria were Streptococcus pneumoniae (2 cases), Haemophilus influenzae (1 case), Klebsiella pneumoniae (1 case), Enterobacter cloacae (1 case). All 5 strains were eradicated. No side effects were observed in any patient, for an efficacy rate of 100%. As for abnormal laboratory findings, elevation of eosinophillia, transaminase and transaminase and ALP were observed in 1 case, 2 and 1 respectively but they were all mild and transient.