Antibacterial properties of human amnion and chorion in vitro

Abstract

Objective: The purpose of the present study was to explore the direct effects of amnion and chorion on bacterial growth in vitro including the antibacterial spectrum. Chorioamniotic membranes were obtained under sterile conditions from 13 healthy women undergoing elective cesarean section at term. Likewise, chorioamniotic membranes were obtained from 10 healthy women with spontaneous vaginal delivery at term. Five strains of Hemolytic streptococci group B (GBS) were tested and one clinical isolate of the following species or bacterial groups: Hemolytic streptococcus group A, Staphylococcus aureus, Staphylococcus saprophyticus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter calcoaceticus and Lactobacillus species. Bacteriological media included (1) blood-agar medium; (2) a transparent agar medium for submerged cultures; and (3) a nutrient broth medium. Results: An inhibitory effect of fetal membranes against a range of bacteria was found. Consistent results were obtained in experiments with cultures on agar and cultures suspended in agar (membranes from eight women in both studies). In experiments with liquid cultures (seven women) only chorion showed a marginal inhibitory effect. All strains were inhibited, but the most pronounced inhibition was obtained for streptococcus group A, S. aureus and S. saprophyticus by both chorion and amnion. Conclusion: This study demonstrated an inhibitory effect of the fetal membranes on a diverse panel of bacteria

Introduction

The etiology of preterm labour is multifactorial, but there is increasing evidence of infection as a cause, and especially vaginal colonization by a number of different microorganisms is associated with preterm delivery [1], [2]. The majority of pregnancies continue until 37–42 weeks’ gestation even when potentially virulent bacteria are present in the vagina. This probably indicates that competent local defence mechanisms protect the feto-maternal unit and a number of studies have implicated factors such as immunoglobulins and cytokines [3], [4].

Antibacterial properties are well described for amniotic fluid [5], and a limited number of studies have pointed to inhibitory effects of fetal membranes [6], [7], [8].

A rapid decline in group B streptococcal viability was observed when group B streptococci (GBS) were added to fetal membranes in an experimental model developed for studying bacterial penetration in vitro [9]. It is intriguing that, for decades, chorioamniotic membranes have been applied therapeutically to ulcerated skin surfaces, peritoneum and the lacerated eye [10], [11]. In recent years, studies have focused on the repairing ability of amnion cells in reconstructions after microsurgery and keratectomy [12], [13].

The purpose of the present study was to further explore the direct effects of amnion and chorion on bacterial growth in vitro, including the antibacterial spectrum. Five strains of GBS were tested and one clinical isolate of the following species or bacterial groups: group A streptococcus, S. aureus, S. saprophyticus, E. faecalis, E. coli, P. aeruginosa, A. calcoaceticus and Lactobacillus species.