Abstract
The endometrium is a challenging site for metagenomic analysis due to difficulties in obtaining uncontaminated samples and the limited abundance of the bacterial population. Indeed, solid correlations between endometrial physio-pathologic conditions and bacteria compositions have not yet been firmly established. Nevertheless, the study of the endometrial microbiota is of great interest due to the close correlations between microbiota profiles, women’s health, and successful pregnancies. In this study, we decided to tackle the study of the endometrial microbiota through analysis of bacterial population in women subjected to elective caesarean delivery. As a pilot study, a cohort of 19 Caucasian women at full term of normal pregnancy and with a prospection of elective caesarean delivery was enrolled for endometrium sampling at the time of caesarean section. Sampling was carried out by endometrial biopsy soon after the delivery of the newborn and the discharge of the placenta and fetal membranes from the uterus. Bacterial composition was established by a deep metabarcoding next generation sequencing (NGS) procedure addressing the V5–V6 hypervariable region of the 16S rRNA gene. Amplicon sequences were analysed by bioinformatic procedures for denoising and taxonomic classification. The RDP database was used as 16S rRNA reference collection. Metabarcoding analysis showed the presence of a common bacterial composition, including six genera classifiable within the human microbiota (Cutibacterium, Escherichia, Staphylococcus, Acinetobacter, Streptococcus, Corynebacterium), that could be part of the core endometrial microbiota under the specific conditions examined. These results can provide useful information for future studies on the correlations between bacteria and successful pregnancies.
Highlights
The human microbiota consists of various microbial populations distributed in the different sites of the body
Evidence from next generation sequencing (NGS) investigations strongly supports the existence of a uterine microbiota and metagenomic approaches are gaining momentum in the analyses of the human endometrial microbiota under different conditions
We focused on the characterization of the uterine microbiomes of women subjected to elective caesarean deliveries at full term of normal pregnancies, since this condition allows direct sampling of the endometrial tissue while avoiding vaginal contaminations
Summary
The human microbiota consists of various microbial populations distributed in the different sites of the body. A more limited number of studies, in cases of women subjected to surgical uterus removal, adopted direct in-utero sampling [20,21,22,23,24] All these studies did not define a clear scenario of the human uterine microbiota and its dynamics in either physiological or pathological conditions, and some discrepancies can be observed among the various analyses (for critical evaluations see the above cited reviews). It would be interesting to study the uterine microbial composition during pregnancy and evaluate any possible correlation with its evolution In this pilot study, we focused on the characterization of the uterine microbiomes of women subjected to elective caesarean deliveries at full term of normal pregnancies, since this condition allows direct sampling of the endometrial tissue while avoiding vaginal contaminations. The presence of Cutibacterium (formerly Propionibacterium [25]) and Lactobacillus genera is discussed
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