PROLONGED PRIOR INFECTION WITH CHLAMYDIA PREVENTS ADVERSE PREGNANCY OUTCOME IN A MURINE MODEL

OBJECTIVE: Our purpose was to compare the rate of adverse pregnancy ou tcome in pregnant mice with lower genital tract chlamydial infection w ho had a prior short chlamydial infection versus a prior long-term inf ection. STUDY DESIGN: A total of 127 female mice were divided into sho rt-term and long-term infection groups. We infected the lower genital tracts with Chlamydia trachomatis. After 7 days in the short-term infe ction group and 30 days in the long-term infection group, we treated t he mice with tetracycline-impregnated chow. After documentation of cur e, the mice were mated and transvaginally reinfected with Chlamydia tr achomatis. Forty-one of the 127 (32%) mice became pregnant. We noted t he number of mice with fetal death and the number of pups present. We cultured the lower uterine segment and the pups for Chlamydia. RESULTS : Seven of 21 (33%) mice in the short-term infection group had fetal d eaths compared with 1 of 20 (5%) in the long-term infection group (p < 0.05). In the short-term infection group 21 of 21 (100%) mice had pos itive transvaginal chlamydial cultures after reinoculation compared wi th only 7 of 20 (35%) in the long-term infection group (p < 0.000004). Seventeen of 21 (81%) mice in the short-term infection group had posi tive chlamydial cultures from the lower uterine segment versus 1 of 20 (5%) in the long-term infection group (p < 0.000001). Sixty-five perc ent of pups in the short-term infection group and none (0%) of the pup s in the long-term infection group were positive for Chlamydia (p < 0. 00001). CONCLUSIONS: We conclude that in this murine model a prior 30- day genital tract infection with Chlamydia protects pregnant mice from subsequent reinfection and adverse pregnancy outcomes.