The antibacterial efficacy of trovafloxacin against an experimental infection with Listeria monocytogenes in hydrocortisone-treated mice

The efficacy of trovafloxacin in treating Listeria monocytogenes infections in glucocorticosteroid-treated mice was compared with the efficacy of amox ycillin. Swiss mice were treated with daily injections of 2.5 mg hydrocorti sone sc and then infected iv with 1 x 10(7) cfu of L. monocytogenes. Untrea ted, this level of infection resulted in 100% mortality between day 3 and d ay 5 after infection. Both sc trovafloxacin and amoxycillin were effective in reducing the number of viable L. monocytogenes in the liver and spleen. Although the MIC of amoxycillin for this isolate of L. monocytogenes was lo wer than that of trovafloxacin (0.063 mg/L versus 0.5 mg/L, respectively), trovafloxacin was more efficacious in vivo after a single dose in the dose range between 12.5 and 100 mg/kg than was amoxycillin, After treatment with trovafloxacin at 100 mg/kg bodyweight od for 3 days, a mean log(10) cfu of 1.58 and 2.52 L. monocytogenes could be recovered from the spleens and liv ers, respectively, whereas after treatment with amoxycillin at 100 mg/kg bo dyweight every 8 h for 3 days, the mean log(10) cfu values were 2.36 and 2. 02, respectively. These differences were statistically not significant. Res ults of the present study show that the antibacterial efficacy of trovaflox acin against L. monocytogenes in our animal model is equivalent to that of amoxycillin.