This study aimed to evaluate the antimicrobial activity of a new quinolone, lascufloxacin, for the treatment of complicated pneumonia caused by Streptococcus pneumoniae and Prevotella intermedia using a neutropenic mice pneumonia mixed-infection model. In this study, one S. pneumoniae and four P. intermedia isolates were utilized. Antimicrobial efficacy was calculated for each isolate as the reduction of the bacterial count comparatively to the non-treated mice (log_{10} colony forming units (cfu)/mL) obtained in the lungs of the treated mice after 24 h. Consequently, the bacterial densities of S. pneumoniae (KY-9) and P. intermedia (335) in the lungs of control animals were 8.20 ± 0.19 log_{10} cfu/mL and 5.26 ± 1.50 log_{10} cfu/mL, respectively. At human-simulated doses, lascufloxacin and levofloxacin showed high antimicrobial activities against not only S. pneumoniae (lascufloxacin: 1.88 ± 0.43 log_{10} cfu/mL, p < 0.001; levofloxacin 4.30 ± 0.75 log_{10} cfu/mL, p < 0.001), but also P. intermedia (lascufloxacin: 1.54 ± 0.57 log_{10} cfu/mL, p < 0.001; levofloxacin: 2.79 ± 0.55 log_{10} cfu/mL, p = 0.0102). Additionally, levofloxacin demonstrated attenuated antimicrobial efficacies against S. pneumoniae in the mixed-infection model compared with that in the single infection model. In contrast, lascufloxacin showed enhanced antimicrobial activities against S. pneumoniae and P. intermedia in the mixed-infection model. In conclusion, lascufloxacin resulted in enhanced efficacies against S. pneumoniae and P. intermedia, in both the single and mixed-infection models used. These data support the clinical utility of lascufloxacin for use against S. pneumoniae and P. intermedia in the treatment of pneumonia.
【저자키워드】 Streptococcus pneumoniae, Lascufloxacin, Pneumonia mixed-infection mouse model, Prevotella intermedia,