LAUSR

Community-acquired pneumonia (CAP) can involve mixed-infection. However, there are few studies investigating its antimicrobial activity in mixed-infection. The aim of this study was to compare the in vivo antimicrobial activity of GRNX and levofloxacin (LVFX) against Streptococcus pneumoniae and Parvimonas micra in a murine pneumonia mixed-infection model. S. pneumoniae D-6888 and P. micra No. 242 were used in this study. Antimicrobial activity was calculated for each isolate as the change in bacterial count of lungs (Δlog10 CFU/mL) obtained in the treated mice after 24 h compared with the count in the starting control animals (0 h). The MICs of GRNX and LVFX against S. pneumoniae D-6888 were 0.06 and 0.5 mg/L. The MICs of these quinolones against P. micra No. 242 were 0.03 and 0.12 mg/L. In a murine pneumonia mixed-infection model, GRNX showed significantly higher in vivo antimicrobial activity against S. pneumoniae than LVFX (GRNX; -2.02 ± 0.99 log10 CFU/mL vs. LVFX; -0.97 ± 0.61 log10 CFU/mL, p = 0.0188). Numerically better activity against P. micra was noted for GRNX therapy in this model (GRNX; -1.12 ± 0.56 log10 CFU/mL vs. LVFX; -0.61 ± 0.43 log10 CFU/mL, p = 0.1029). These results suggested that GRNX has potential to be a preferable treatment for CAP.