Peritoneal fluid microbiota profile of patients with deep endometriosis

Endometriosis is a chronic gynecological disease that affects 10 % of reproductive-aged women and characterized by the presence of endometrial tissue outside the uterus. The disease is linked to a pro-inflammatory environment in the peritoneal fluid of patients, with high levels of cytokines, growth factors, and reactive oxygen species. Changes in the peritoneal fluid, such as altered immune cells and cytokines, can be linked to the immune balance in endometriosis. Immunological changes may be related to the presence of microorganisms in the peritoneal fluid that can activate Toll-like receptor (TLR) signaling and trigger an inflammatory response. A high diversity of TLRs has been found in women with endometriosis, and the presence of specific microorganisms in the fluid is suggested to be responsible for the activation of inflammasomes and inflammatory cytokines involved in the development of endometriosis. The present study was conducted at a hospital in southeastern Brazil to test this hypothesis, using a case-control design. Peritoneal fluid from 50 patients was used in this study. The case group consisted of 27 patients with endometriosis and the control group consisted of 23 patients without endometriosis. The samples were stored in a microbiome transport solution, and DNA was extracted and sent for genetic sequencing to identify the microorganisms present. The obtained sequencing reads were processed using a bioinformatics pipeline involving demultiplexing with the Illumina proprietary software, primer detection and removal, error evaluation, quality filtering, error removal using the Deblur software, amplicon sequence variants grouping, and chimera detection using the VSEARCH software. The sheer abundance of the microbiome made it challenging to discern any notable differences between the two groups. Nevertheless, we highlighted the prevalence of three primary bacteria in the peritoneal fluid from patients with endometriosis: Flavobacterium, Pseudomonas, and Bacillus. The results were established after a rigorous experimental design to eliminate potential contamination from extraction kits and handling. Our findings provide valuable insight into the pathogenesis of this disease and can be useful to understand how microbiota and immune system works in endometriosis.