The effect of a single oral dose of azithromycin on chlamydial salpingitis in mice.

Progesterone-treated C3H mice were inoculated under the ovarian bursa with a human Chlamydia trachomatis strain, serovar E, and treated variously from one week before inoculation to two weeks afterwards with a single oral dose of azithromycin. At autopsy, all 27 control mice, not given azithromycin, had histological evidence of salpingitis. Any tubal inflammation in the 139 mice which had received greater than or equal to 60 mg azithromycin/kg was always less severe than that in control mice killed on the same day. This was true also for three of the six mice given azithromycin 25 mg/kg. Salpingitis was prevented in all 38 mice given greater than or equal to 60 mg of azithromycin on the day chlamydiae were inoculated. Inflammation was found in only 35% of mice given 60-80 mg/kg of drug from two to ten days after inoculation and was less severe than in untreated control mice. This dose given later was not as effective in preventing disease. Doses of 200-240 and 100-180 mg/kg given up to a week before inoculation reduced the proportion of mice with salpingitis to 33% and 77%, respectively, while no reduction occurred with 60-80 mg/kg, although lesions were less severe than in control mice. Chlamydiae were not detected in any part of the genital tract when greater than or equal to 60 mg/kg of azithromycin were given on the day of inoculation and were rarely detected when the drug was given a week before or up to 12 days after inoculation. Re-isolation of organisms was not always associated with histological evidence of disease.(ABSTRACT TRUNCATED AT 250 WORDS)