The effect of a single oral dose of azithromycin on chlamydial infertility and oviduct ultrastructure in mice

Azithromycin has been recommended for the treatment of human chlamydial genital tract infections because of the sustained, chlamydicidal levels of the antibiotic which can be achieved after a single dose. The effect of single dose azithromycin on the prevention or reversal of chlamydial-induced damage to the oviduct or to fertility was assessed in a mouse model of chlamydial salpingitis which closely mimics the human disease. C3H mice were treated with progesterone and then inoculated under the ovarian bursa with a human genital tract isolate of Chlamydia trachomatis, serovar F. Azithromycin at doses from 135-250 mg/kg was administered by oral intubation. Morphological damage to the oviduct lumen was assessed by scanning electron microscopy, while fertility was assessed by breeding experiments. Treatment of mice two or seven days after infection with 135 mg/kg azithromycin completely reversed chlamydial-induced ultrastructural changes and infertility. Treatment 12 or more days after infection, at doses as high as 250 mg/kg, failed to prevent infertility. The onset of fertility correlated with the loss of ciliated epithelia from the oviduct. However, the regeneration of ciliated epithelia following azithromycin treatment did not necessarily restore tubal patency. These results, if true for women also, indicate the need for rapid, effective antibiotic therapy for chlamydial salpingitis to prevent infertility and other sequelae of tubal damage.