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

The in vitro antimicrobial activity of pazufloxacin (PZFX), a new- quinolone agent for oral use developed in Japan, and its therapeutic efficacy in the treatment of respiratory tract infections were evaluated. The minimum inhibitory concentrations (MICs) of PZFX, ofloxacin (OFLX), ciprofloxacin (CPFX), tosufloxacin (TFLX), sparfloxacin (SPFX), cefaclor (CCL) and rifampicin (RFP) against 20 strains each of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin resistant S. aureus (MRSA), Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Pseudomonas aeruginosa, 18 strains each of Haemophilus influenzae and Mycobacterium intracellulare, 22 strains each of Mycobacterium tuberculosis and Mycobacterium avium were determined by the micro-broth dilution method using the Dynatech MIC 2000 system. As shown by MICs, PZFX was as active as OFLX against MSSA, MRSA, H. influenzae, E. coli, K. pneumoniae, E. cloacae and S. marcescens. PZFX was more active than OFLX against P. aeruginosa, but less active than OFLX against Mycobacteriaceae. Twenty-eight patients received a daily dose of 300 mg to 600 mg of PZFX per os for 3~14 days (mean: 11.6 days): one patient with acute bronchitis. 10 patients with pneumonia, 11 patients with infection associated with bronchiectasis, 4 patients with infection associated with pulmonary emphysema, and one patient each with infection associated with bronchial asthma et old pulmonary tuberculosis. The clinical effects were excellent in 3, good in 16 and poor in 6 patients (efficacy rate: 76%). Three cases were excluded from clinical evaluation. Twelve strains were identified as causative organisms: Three strains each of S. aureus and H. influenzae, two strains each of Streptococcus pneumoniae and P. aeruginosa, one strain each of Streptococcus pyogenes and Klebsiella oxytoca. Six of 12 strains were eradicated and one strain was decreased in number by administration of PZFX. Rash and dizziness were observed in one patient each during treatment with PZFX. Elevation of s-GPT, leucocytopenia, and eosinophilia were observed in one patient each. These adverse reactions disappeared after completion of therapy. We conclude from the above results that PZFX is one of the most useful quinolone agents for oral use as a drug of first choice in the treatment of respiratory infections.