P-340 Microbial composition of the female reproductive tract in endometriosis: a pilot study
I Leonés Baños, B A Folch, E Salas-Espejo, M Gámiz-Aguilera, I Pérez-Prieto, A Sola-Leyva, J Fontes, R Sánchez, L Martínez-Navarro, S AltmäeAbstract
Study question
Does the microbial composition along the female reproductive tract (vagina, cervix and uterus) differ between women with and without endometriosis?
Summary answer
Slight differences in the microbial composition along the female reproductive tract suggest that at genus level the microbes do not seem to associate with endometriosis.
What is known already
Endometriosis is a chronic inflammatory disease affecting 200 million women worldwide, characterized by the painful growth of endometrial tissue outside the uterus, significantly impacting quality of life in women affected. Patients often present comorbidity with other inflammatory diseases and experience high infertility rates. Although its etiology remains unknown, imbalances in the vaginal and endometrial microbiota have been linked to its development.
Study design, size, duration
This study included 34 women (mean age ± SD = 34.21 ± 3.55 years; BMI ± SD = 24.29 ± 3.84), 16 women with active endometriosis and 18 controls. Participants were recruited at the Reproduction Unit of the Virgen de las Nieves University Hospital between 2019 and 2021. Each participant provided vaginal and cervical swab samples, and endometrial sample with TaoBrush device.
Participants/materials, setting, methods
Each participant underwent an LH test to determine the menstrual cycle day, and samples were collected 7–9 days after the LH peak, during the implantation window. Vaginal, cervical, and uterine microbiomes were analyzed using 16S rRNA (V4) sequencing. Contamination control in uterine samples included negative controls and in silico decontamination (MicroDecon). Microbial diversity and composition analyses were adjusted for age, BMI and antimicrobial use (antibiotics, antivirals or antifungals) as confounders.
Main results and the role of chance
A total of 102 samples from different body sites were analyzed for microbial composition. Within-sample diversity (i.e., alpha-diversity) was estimated by Shannon diversity index and observed genera (Richness). Between-sample dissimilarity (beta-diversity) was visualized using Principal Coordinates Analysis (PCoA). 22 bacterial genera were differentially abundant along the female reproductive tract between women with endometriosis and control women. Specifically, 7 bacteria in the endometrium, 3 in the cervix and 5 in the vagina were more prevalent, while 6 in the endometrium and 1 in the vagina were less prevalent in the endometriosis group. However, these differences were not statistically significant after false discovery rate (FDR) correction. In the endometriosis group, the most prevalent genera were Streptococcus, Prevotella, Pseudomonas, Enterococcus, Acinetobacter and Escherichia, among others.
Limitations, reasons for caution
These first pilot study results require confirmation in larger sample sizes. Assessing microbial composition using 16S rRNA gene V4 region sequencing enabled microbial identification on genus level. Future studies should analyse microbial species and microbiome functionality to unravel the microbial involvement in endometriosis.
Wider implications of the findings
Endometriosis affects 10% of reproductive-age women. Identifying factors that could trigger or influence its development are essential for earlier detection of the disease and for developing possible treatment solutions.
Trial registration number
No