Bacterial Communities in the Womb During Healthy Pregnancy

Lihong Zhu,Huajun Zheng,Yang Han,Jinhong Qin,Fei Luo,Yuezhu Wang,Xiaokui Guo,Wenjing Hu

doi:10.3389/fmicb.2018.02163

Abstract

The idea that healthy uterine cavity is sterile is challenged nowadays. It is still debatable whether the bacteria present in the uterine cavity during pregnancy are residents or invaders. To reveal microbiome composition and its characteristics in the womb of pregnant women, 41 decidual tissue samples and 64 amniotic fluid samples were taken from pregnant Chinese women. DNA extraction was followed by pyrosequencing of the hypervariable V4 region of the 16S rDNA gene to characterize womb microbiome. Both types of samples had low diversity microbiome with Enterobacteriaceae being the dominant phylotypes at family level. To characterize the nature of colonization during pregnancy, the presence of endogenous biomass was confirmed by cultivation. Surprisingly, all of the 50 amniotic fluid samples studied were culture-negative, whereas 379 out of 1,832 placenta samples were culture-positive. Our results suggested that womb contained microbiome with low diversity. Culture-based investigation of amniotic fluid and placenta samples confirmed the presence of cultivable microorganisms in the placenta but not in amniotic fluid. Thus it suggests that bacterial colonization does occur during healthy pregnancy.

Highlights

It was widely thought that the womb is a sterile environment during healthy pregnancy (Funkhouser and Bordenstein, 2013)
Microorganisms with relative abundance of >0.1% at the family level in two types of samples showed that Enterobacteriaceae accounted for 88.6% of the relative abundance in decidual tissue and for 40.3% in amniotic fluid
Detailed comparisons at the genus level across the two types of samples showed that Firmicutes were more abundant in decidual tissue than in amniotic fluid (Figure 1B) and 10 taxa, e.g., Propionibacterium, Bacillales spp., Anoxybacillus, Caulobacteraceae spp., Methylobacteriaceae spp., Methylobacterium, Phyllobacterium, Sphingomonas, Comamonadaceae spp., and Deinococcus were unique in amniotic fluid

Summary

Introduction

It was widely thought that the womb is a sterile environment during healthy pregnancy (Funkhouser and Bordenstein, 2013). The presence of bacteria in uterine cavity was considered as a risk factor because they could potentially affect the fetus and cause systemic inflammation and multiple organ damage (Martius and Eschenbach, 1990). The bacteria invading uterine cavity have been postulated to emerge mainly from the lower urogenital tract, ascending upward through the cervix to the uterus and breaching the placental barrier to amniotic fluid and placenta (Goldenberg et al, 2000; Keelan and Payne, 2015). In uterine cavity confirmed by culture-dependent or cultureindependent methods has been frequently associated with negative pregnancy outcomes (Han et al, 2004, 2009, 2010). Despite the undoubtedly strong associations, these species have not been conclusively shown to be pathological agents. This circumstance indicates that available findings may have complex interpretation

Methods

Results

Conclusion