Roxithromycin treatment of mouse chlamydial salpingitis and protective effect on fertility.

We used a mouse model of acute chlamydial salpingitis to evaluate the efficacy of roxithromycin in preventing irreversible inflammatory damage leading to tubal infertility. Female C3H/He mice were genitally inoculated with a human strain of Chlamydia trachomatis and then treated with roxithromycin glutamate subcutaneously. Treatment was initiated either 7 or 10 days postinfection (p.i.) and continued for 7 days at a dosage of 50 or 100 mg/kg of body weight per 24 h. The course of the disease was monitored serologically, bacteriologically, and histologically. At the end of the treatment, the mice were encaged with males and their reproductive capacity was recorded over a 19-week period. The protective effect of roxithromycin was assessed in terms of fertility parameters in comparison with values for noninfected control mice. When treatment was initiated on day 7 p.i. and given in twice-daily 25-mg/kg doses, all the mice remained fertile and the total number of offspring was similar to that of sham-infected mice (17.3 +/- 3.3 versus 17.2 +/- 2.3). When treatment was initiated on day 10 p.i. and given in a single daily dose of 50 or 100 mg/kg, 90 and 70% of the mice, respectively, remained fertile; however, in terms of total offspring, fertility was lower in the group treated with the lower dose (5.6 +/- 1.4 versus 13.0 +/- 3.8). Roxithromycin was found to be effective against C. trachomatis in the mouse genital tract, but fertility was only partially preserved when the time between infection and treatment was prolonged.