EXPERIMENTAL GENITAL MYCOPLASMOSIS - TIME OF INFECTION INFLUENCES PREGNANCY OUTCOME

Genital infection of rats with Mycoplasma pulmonis causes adverse preg nancy outcome and can result in in utero spread of infection to the fe tus. The current study was designed to determine whether the stage of pregnancy when infection occurs influences pregnancy outcome. Rats wer e inoculated with 3 x 10(7) CFU of M. pulmonis at 10 days prior to bre eding (-10) or at gestational day (gd) 11 or 14 and were necropsied at gd 11, 14, or 18 or within 24 h of parturition (term). Control rats r eceived sterile broth, M. pulmonis was isolated from the placenta, amn iotic fluid, or fetal tissues only from rats infected prior to breedin g (P < 0.001), All infected rats had significantly more loss of pups t han did control rats (P < 0.006), but rats infected prior to breeding or at the beginning of the third trimester (gd 14) were much more like ly to have fetal losses. Rats infected in the early second trimester a fter implantation (gd 11) did not experience severe losses, Litter siz es, total litter weight, and individual pup weight from all infected r ats, regardless of gestational stage when infected, were significantly smaller than those of control rats (P < 0.001). On the basis of the r esults of this study, we conclude that the time of infection plays a m ajor role in determination of pregnancy outcome and spread of infectio n from the genital tract to the respiratory tract.