In vitro antimicrobial activity, penetration into sputum and therapeutic efficacy of grepafloxacin in respiratory tract infections

The in vitro antimicrobial activity, serum and sputum concentrations of grepafloxacin (GPFX), a newquinolone agent for oral use developed in Japan, and its therapeutic efficacy in the treatement of respiratory tract infections were evaluated. The minimum inhibitory concentrations (MICs) of GPFX, ofloxacin (OFLX), ciprofloxacin (CPFX), tosufloxacin (TFLX), sparfloxacin (SPFX) and rifampicin (REP) against 20 strains each of mechicillin-susceptible Staphylococcus aureus (MSSA), methicilinresistant S. aureus (MRSA), Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Pseudomonas aeruginosa and Mycobacterium avium, and 18 strains each of Haemophilus influenzae and Mycobacterium tuberculosis were determined by the micro-broth dilution method using the Dynatech MIC 2000 system. As shown by MICs, GPFX was more active than OFLX against all the species tested except for S. marcescens, against which it was as active as OFLX. The ratio of the concentration of GPFX in sputum to that in serum after oral administration of 200 mg was 161%. Twenty-two patients received a daily dose of 200 mg to 300 mg of GPFX per os for 7~14 days (mean: 11.1 days): 4 with chronic bronchitis, 3 with infection associated with bronchial asthma, 6 with infection associated with bronchiectasis and 9 with pneumonia. The clinical effects were excellent in 6, good in 12, fair in 2 and poor in 2. Twelve strains were identified as causative organisms. Eleven strains were eradicated and one strain (P. aeruginosa) was decreased in number by administration of GPFX. No clinical adverse effects were observed during treatment with GPFX. Eosinophilia and a transient elevation of serum transaminase were observed in one patient each. These adverse effects disappeared after the completion of therapy. We conclude from the above results that GPFX is one of the most useful quinolone agents for oral use as a drug of first choice in the treatment of respiratory infections, especially in outpatient clinics.