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 membranes from seventeen healthy women were mounted onto glass cylinders and placed in tissue culture trays constituting a two-compartment system with a maternal compartment internally and a fetal compartment externally. GBS from healthy pregnant women and from newborn babies with sepsis were added to the maternal compartment at densities from 10(7) to 10(9) colony forming units (cfu) per ml. Results. Irrespective of inoculum density, GBS was not recovered from the fetal compartment within a 20 h incubation period. By histology, micro-colonies of GBS were found on the maternal surface after 8 h, but 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 membranes appear to constitute an effective barrier against ascending infection. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.