In vitro and in vivo antibacterial activities of garenoxacin against group G Streptococcus dysgalactiae subsp. equisimilis.

In this study, garenoxacin showed potent in vitro activity against clinical isolates of group G Streptococcus dysgalactiae subsp. equisimilis [minimum inhibitory concentration for 90% of the organisms (MIC(90)) = 0.125 μg/mL] and was superior to levofloxacin (MIC(90) = 1 μg/mL) and moxifloxacin (MIC(90)=0.25 μg/mL). In experimental pneumonia caused by group G S. dysgalactiae subsp. equisimilis in mice, the effective dose for 50% survival (ED(50)) of garenoxacin following single oral administration was 1.87 mg/kg, >10.7-fold and 4.6-fold less than the ED(50) values of levofloxacin (>20 mg/kg) and moxifloxacin (8.54 mg/kg), respectively. The area under the free serum concentration-time curve from 0-24 h (fAUC(0-24))/MIC ratio of garenoxacin in serum following oral administration of 20 mg/kg was 73.2, which was 8.7-11.4-fold and 1.4-fold greater than that of levofloxacin (6.44-8.46) and moxifloxacin (51.4), respectively. These results suggest that garenoxacin has potential for the treatment of infectious diseases caused by S. dysgalactiae subsp. equisimilis.