Endometrial microbiota profile in in-vitro fertilization (IVF) patients by culturomics-based analysis

Abstract

IntroductionIt is well recognized that the human uterus and adjoining tissues of the female reproductive tract exist in a non-sterile state where dysbiosis can impact reproductive outcomes. The endometrial microbiota is a part of this greater milieu. To date, it has largely been studied using 16S rRNA or metagenomics-based methodologies. Despite the known advantages of sequencing analysis, several difficulties have been noted including sample contamination and standardization of DNA extraction or sequencing. The aim of this study was to use a culturomics-based method to analyze the endometrial microbiota and correlate the results with ongoing pregnancy rates.MethodsA prospective cohort study was performed at the University of Naples from June 2022 to December 2022. Ninety-three patients undergoing an IVF cycle with single embryo transfer (ET) (fresh or frozen) were enrolled in the study. Following ET, the catheter tip was inserted into brain heart infusion (BHI) medium under sterile conditions for culture. After 24h and 48h of incubation the microorganisms in the colonies were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).ResultsOverall, 68 (73,92%) patients resulted positive for one or more microbes and 25 patients (26,08%) had no microbial growth. Across all participants, the four most important phyla were Firmicutes (87,76%), Proteobacteria (27,94%), Actinobacteria (10,29%) and Ascomycota (8,82%). Lactobacillus species, in particular, was significantly correlated with ongoing pregnancy rate (p=0,05). On the other hand, Staphylococcus subspecies (spp.) (p<0,05) and Enterobacteriaceae (p<0,001) were found to have a negative impact on the implantation rate.DiscussionDetection of bacteria by culturomics from catheter tips used for embryo transfer has been shown to be a reliable method to detect pathogen growth. Endometrial microbiota testing in clinical practice could certainly offer a means to further improve diagnosis and treatment strategies in IVF patients.

Effect of environmental factors on seminal microbiome and impact on sperm quality

“…Conversely, a study applying sequencing of variable regions 3 and 4 of the 16S rRNA found no differences in seminal microbiome composition and diversity between male partners of couples that had or did not have a successful pregnancy after intrauterine insemination ( 91 ). On the female side, a recent analysis of the endometrial microbiome of women undergoing IVF demonstrated that 73.9% of the endometrial samples assessed with NGS were colonialized by one or more microbes, further highlighting the fact that human reproduction often happens in the presence of a bacterial microbiota ( 92 ). Figure 5 summarizes the main bacterial phyla or genera associated with fertility status and outcomes.…”

Special series on the role of the microbiome in reproduction and fertility

“…Studies have shown that the bacterial composition of the vaginal microbiome can influence the success rate of IVF procedures, with specific microbial profiles associated with improved implantation and pregnancy rates ( Franasiak et al 2021 ). Furthermore, emerging evidence suggests that the microbiome of the embryo culture medium used during IVF may impact embryo development and viability ( Cariati et al 2023 ).…”