Bacterial communities found in placental tissues are associated with severe chorioamnionitis and adverse birth outcomes

Abstract

Preterm birth is a major cause of neonatal mortality and morbidity worldwide. Bacterial infection and the subsequent inflammatory response are recognised as an important cause of preterm birth. It is hypothesised that these organisms ascend the cervical canal, colonise placental tissues, cause chorioamnionitis and in severe cases infect amniotic fluid and the foetus. However, the presence of bacteria within the intrauterine cavity does not always precede chorioamnionitis or preterm birth. Whereas previous studies observing the types of bacteria present have been limited in size and the specificity of a few predetermined organisms, in this study we characterised bacteria found in placental tissues from a cohort of 1391 women in rural Malawi using 16S ribosomal RNA gene sequencing. We found that specific bacteria found concurrently on placental tissues associate with chorioamnionitis and delivery of a smaller newborn. Severe chorioamnionitis was associated with a distinct difference in community members, a higher bacterial load and lower species richness. Furthermore, Sneathia sanguinengens and Peptostreptococcus anaerobius found in both matched participant vaginal and placental samples were associated with a lower newborn length-for-age Z-score. This is the largest study to date to examine the placental microbiome and its impact of birth outcomes. Our results provide data on the role of the vaginal microbiome as a source of placental infection as well as the possibility of therapeutic interventions against targeted organisms during pregnancy.

Lack of evidence for microbiota in the placental and fetal tissues of rhesus macaques

“…Staphylococcus is a genus of bacteria commonly associated with mammalian skin and mucosal surfaces (91). It was detected in a preliminary molecular survey of the fetus and placenta of the Japanese macaque (85) and it has also been reported in numerous DNA sequence-based investigations of the human placenta (31–38, 41–43). However, Staphylococcus has also been identified as a background DNA contaminant in sequence-based studies (48), including in several prior studies of the human placenta (39, 57, 62).…”

The development and ecology of the Japanese macaque gut microbiome from weaning to early adolescence in association with diet

“…Given our observations of maternal dietary influence, it is intriguing to postulate when this early life influence is occurring. We and others have previously demonstrated that we can employ metagenomics and 16S sequencing to detect and characterize a unique and low abundance, low biomass placental and neonatal microbiome (Aagaard et al, ; Amarasekara, Jayasekara, Senanayake, & Dissanayake, ; Antony et al, ; Ardissone et al, ; Bassols et al, ; Borghi et al, ; Chu et al, ; Chu et al, ; Collado, Rautava, Aakko, Isolauri, & Salminen, ; Doyle et al, ; Doyle et al, ; Gomez‐Arango et al, ; Jiménez et al, ; Leon et al, ; Martinez et al, ; Parnell et al, ; Prince et al, ; Rautava, Collado, Salminen, & Isolauri, ; Satokari, Grönroos, Laitinen, Salminen, & Isolauri, ; Zheng et al, ). Furthermore, in an elegant set of experiments, Li et al (2019) recently demonstrated that memory CD4 + T cells are generated during intrauterine development in the human fetal intestine, which are phenotypically similar to innate‐like lymphocytes previously described in mice that are dependent on microbes for their maintenance (Prince et al, ).…”

Microbial translocation into amniotic fluid of vervet monkeys is common and unrelated to adverse infant outcomes

“…11 Other studies have detected bacteria utilizing PCR assays and culture, but differ on their findings of correlation with pre-term labor and delivery. [2][3][4][5][6][7] Therefore, this study has great implications beyond correlating to infant mortality within a closed colony due to the differing and opposing previously reported results.…”

“…There have been many published reports regarding the topic of intra-amniotic sterility; however, these reports tend to contradict one another in terms of bacteria and correlation with pre-term labor and delivery. [2][3][4][5][6][7] Our study aimed to analyze the sterility of amniotic fluid from vervet monkeys in a colony with a poor reproductive history. We hypothesized that microbial contamination would be higher in pregnancies that terminate as pre-term or stillbirth.…”