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 (MIC90) = 0.125 μg/mL] and was superior to levofloxacin (MIC90 = 1 μg/mL) and moxifloxacin (MIC90 = 0.25 μg/mL). In experimental pneumonia caused by group G S. dysgalactiae subsp. equisimilis in mice, the effective dose for 50% survival (ED50) of garenoxacin following single oral administration was 1.87 mg/kg, >10.7-fold and 4.6-fold less than the ED50 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 (fAUC0–24)/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.