IN UTERO TRANSMISSION OF MYCOPLASMA-PULMONIS IN EXPERIMENTALLY INFECTED SPRAGUE-DAWLEY RATS

Genital mycoplasmosis is important as an animal model for the interact ion between infectious agents and the host during pregnancy as well as in its own right as a confounding variable affecting research project s in which the rat is used as a model to study reproductive function a nd physiology. We report the in utero transmission of Mycoplasma pulmo nis and the development of placentitis, amnionitis, and mild fetal bro nchopneumonia in Sprague-Dawley rats. A minimum of 10 days prior to br eeding, specific-pathogen-free female Sprague-Dawley rats were infecte d by intravaginal inoculation with 3 x 10(7) CFU of M. pulmonis X1048 or with an equal volume of sterile broth. Rats and fetuses were subjec ted to necropsy at days 11, 14, and 18 of gestation. M. pulmonis was a ble to invade the placenta, cross the placental barrier, and establish an amniotic fluid infection by gestational day 14. It was isolated fr om the oropharynx and lungs of fetuses at gestational day 18. The plac enta was more frequently colonized than amniotic fluid, followed by th e fetal oropharynx and lungs, supporting an ascending route of infecti on. Histopathological evidence also support an active infection, with lesions compatible with placentitis, amnionitis, and mild fetal bronch opneumonia. M. pulmonis can traverse the placenta, resulting in infect ion of the amniotic fluid and in utero transmission of the microorgani sm to the developing fetus.