Bacteroides fragilis, Streptococcus intermedius and group B streptococci in ascending infection of pregnancy. An animal experimental study.

By means of bacteriological, histological and immunofluorescence methods, the ascending spread of endocervically inoculated bacteria was studied in 14 pregnant sheep. 8 ewes near term were exposed to group B streptococci, Bacteroides fragilis or Streptococcus intermedius for 2-4 days. 6 other animals in mid pregnancy were exposed to one of the bacteria mentioned for 30 days. Before inoculation, aerobic and anaerobic culture specimens from cervix and amniotic fluid were obtained. At delivery by caesarean section, in addition to culture specimens, membrane and placental tissues were collected. Bacterial detection by means of indirect immunofluorescence showed significant invasion of the membranes and the placentas by the microorganisms inoculated. In one case, inoculated with S. intermedius, the ascending infection could be shown to pass the intact membranes reaching the amniotic fluid. It is concluded that endocervical bacteria in the indigenous microflora might cause pregnancy complications by establishing ascending infection. Furthermore, as the bacteria tested have been implicated in premature rupture of the membranes, an aetiological role of ascending infection in this pregnancy complication is postulated.