Chorioamniotic membranes constitute a competent barrier to group b streptococcus in vitro

Objective: To study the penetration of group B streptococcus (GBS) through human chorioamniotic membranes in vitro. Study design: Chorioamniotic membr anes from seventeen healthy women were mounted onto glass cylinders and pla ced in tissue culture trays constituting a two-compartment system with a ma ternal compartment internally and a fetal compartment externally. GBS from healthy pregnant women and from newborn babies with sepsis were added to th e maternal compartment at densities from 10(7) to 10(9) colony forming unit s (cfu) per ml. Results. Irrespective of inoculum density, GBS was not reco vered from the fetal compartment within a 20 h incubation period. By histol ogy, micro-colonies of GBS were found on the maternal surface after 8 h, bu t invasion of the morphologically intact membranes was not observed. A five log reduction in cfu occurred in the maternal compartment with amnion when GBS were suspended in saline. Conclusion: In this in vitro model the membr anes appear to constitute an effective barrier against ascending infection. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.