The placental membrane microbiome is altered among subjects with spontaneous preterm birth with and without chorioamnionitis

Abstract

BACKGROUND Preterm birth (PTB) is a leading cause of neonatal morbidity and mortality and is not uncommonly associated with chorioamnionitis. We recently have demonstrated that the placenta harbors a unique microbiome with similar flora to the oral community. We also have shown an association of these placental microbiota with PTB, history of antenatal infection, and excess maternal weight gain. On the basis of these previous observations, we hypothesized that the placental membranes would retain a microbiome community that would vary in association with preterm birth and chorioamnionitis. OBJECTIVE In the current study, we aimed to examine the differences in the placental membrane microbiome in association with PTB in both the presence and absence of chorioamnionitis and/ or funisitis using state-of-the-science whole-genome shotgun metagenomics. STUDY DESIGN This was a cross-sectional analysis with 6 nested spontaneous birth cohorts (n = 9–15 subjects/cohort): Term gestations without chorioamnionitis, term with chorioamnionitis, preterm without chorioamnionitis, preterm with mild chorioamnionitis, preterm with severe chorioamnionitis, and preterm with chorioamnionitis and funisitis. Histologic analysis was performed with Redline's criteria, and inflammatory cytokines were analyzed in the cord blood. DNA from placental membranes was extracted from sterile swabs collected at delivery, and whole-genome shotgun sequencing was performed on the Illumina HiSeq platform. Filtered microbial DNA sequences were annotated and analyzed with MG-RAST (ie, Metagenomic Rapid Annotations using Subsystems Technology) and R. RESULTS Subjects were assigned to cohorts on the basis of gestational age at delivery and independent scoring of histologic chorioamnionitis. We found that preterm subjects with severe chorioamnionitis and funisitis had increases in cord blood inflammatory cytokines. Of interest, although the placental membrane microbiome was altered in association with severity of histologic chorioamnionitis (permutational multivariate analysis of variance P = .005), there was no observable impact with either beta-methasone or antibiotic treatment. In preterm subjects with chorioamnionitis, we found a high abundance of both urogenital and oral commensal bacteria. These alterations in the microbiome were accompanied by significant variation (P < .05) in microbial metabolic pathways important in the glucose-fed pentose phosphate pathway (term subjects), or glycerophopholipid metabolism, and the biosynthesis of the siderophore group nonribosomal peptides (preterm subjects). CONCLUSION Consistent with ours and others previous findings, women who experienced spontaneous PTB harbor placental microbiota that further differed by severity of chorioamnionitis. Integrative meta-genomic analysis revealed significant variation in distinct bacterial metabolic pathways, which we speculate may contribute to risk of preterm birth with and without severe chorioamnionitis.

The Human Ureaplasma Species as Causative Agents of Chorioamnionitis

“…Furthermore, whole-genome shotgun sequencing of placental membranes (fetal chorion and/or villous placental membranes) from term deliveries without chorioamnionitis demonstrated the presence of a diverse range of bacteria, including Enterobacter spp., E. coli, Acinetobacter lwoffii, Acinetobacter johnsonii, and Lactobacillus crispatus (120). These findings redefine our understanding of the placental microenvironment and challenge the view that the fetus exists normally within a sterile compartment.…”

“…The bacterial pathogens that are most frequently isolated in cases of chorioamnionitis include the human Ureaplasma species (Ureaplasma parvum and Ureaplasma urealyticum), Fusobacterium spp., Streptococcus spp., and, less frequently, Gardnerella spp., Mycoplasma spp., and Bacteroides spp. (1,62,120,(122)(123)(124). Other studies have identified that the sexually transmitted pathogens Chlamydia trachomatis and Neisseria gonorrhoeae, along with the uropathogen E. coli and yeast Candida spp., are also infrequently associated with chorioamnionitis (122,(125)(126)(127)(128).…”

“…Further investigations confirmed the finding that placental infections with Ureaplasma spp. are strongly associated with chorioamnionitis, using wholegenome shotgun sequencing of late preterm and term placentae (120). Similarly, another study has reported that preterm placentae infected with Ureaplasma spp.…”

“…Of the microorganisms associated with chorioamnionitis, the human Ureaplasma spp. are consistently identified as the most common microorganisms within the amniotic fluid and placentae of women with chorioamnionitis (1,62,123,133,134), funisitis (120,135,136), and preterm birth (1,137).…”

Impact of maternal nutrition in pregnancy and lactation on offspring gut microbial composition and function

“…65,66 However, as aforementioned, the vagina tends to predominately be populated by Lactobacillus species before pregnancy, and tends to be further enriched for Lactobacilli as the pregnancy progresses. [46][47][48] Although Lactobacillus species have been detected in the placental membranes in healthy, term pregnancies by Next-Gen sequencing, 67 the overall diversity of commensal species found within the placental parenchyma, amniotic fluid and neonatal meconium suggest that the vaginal microbiome is unlikely to be the only origin for the full gamut of microbial species found within the intrauterine space. Nevertheless, well-designed animal studies are required to further refine these observations and better define a model of microbial transmission during this period.…”