Comprehensive Study of Intestinal Microbiota Using Molecular Genetic and Cultural Methods with an Assessment of the Role of Fecal Biomarkers in Endometriosis

Aim. Analysis of the composition of intestinal microbiota in patients with endometriosis and determination of the potential value of fecal biomarkers in the diagnosis of the disease. Design. Сross-sectional, single-center clinical study. Materials and methods. The clinical and anamnestic data of 260 women with endometriosis (mean age 28 (25; 33) years) were analyzed. A comparison group of 130 age-matched women without signs of genital endometriosis was selected to study symptoms and comorbid conditions of endometriosis. In order to measure the concentrations of fecal markers, 56 women of the main group and 21 of the comparison group were randomized, fecal samples of 37 patients with endometriosis and 22 women of the comparison group were selected for microbiological examination. Microbiological examination of fecal samples was performed by culture and quantitative real-time polymerase chain reaction (PCR) methods, and the concentrations of fecal markers (calprotectin, hemoglobin, transferrin) were estimated by the HTSA Plus immunochemical method in the same biological material. Results. Every 4th patient with endometriosis had complaints of dyschezia (68/260, 26.2%), and more than 60% reported changes in stool character during menstruation in the form of loosening or constipation (161/260, 61.9%). Analysis of gastrointestinal tract (GIT) pathology showed that 77 (29.6%) patients had concomitant organic GIT diseases, i. e. 1.4 times more often than in the comparison group, 60 (23,1%) had irritable bowel syndrome (IBS). The presence of complaints of stool changes during menstruation increased the chances of diagnosing endometriosis 2-fold, concomitant IBS — 5-fold, and dyschezia more than 16-fold. Every 2nd patient with endometriosis (27/56, 48.2%) had a fecal calprotectin concentration greater than reference values, which was also positively correlated with symptoms of intestinal dysbiosis (r = 0.397, p = 0.0025). Analysis of the composition of the intestinal microbiota showed a decrease in species richness, an increase in the frequency and titer of opportunistic microorganisms and a decrease in the colonization of symbiont bacteria in endometriosis. The realtime PCR method had advantages for additional detection of complexly cultured microorganisms; a decrease in the titer of symbiont bacteria of the Clostridium leptum gr. cluster (p = 0.02808), Faecalibacterium prausnitzii (p = 0.03635) and Akkermansia muciniphila (p = 0.05297), microorganisms of the family of the genus Desulfovibrio (p = 0.04852) was detected. Conclusion. An important stage of clinical and anamnestic examination of patients with endometriosis, in addition to the detection of IBS, is the assessment of the presence of organic pathology of the gastrointestinal tract and a number of gastrointestinal symptoms, which can increase the chances of diagnosing endometriosis up to 16 times. Studying the composition of the intestinal microbiota in endometriosis is a promising direction, it is advisable to comprehensively determine the microbial composition by culture and quantitative real-time PCR methods using an extended multiplex panel. Measurement of faecal marker levels seems to be a promising but insufficiently studied method for non-invasive diagnosis of endometriosis, which requires additional studies with a larger sample of patients with colorectal endometriosis. Keywords: endometriosis, intestinal microbiota, culturomics, real-time polymerase chain reaction, faecal calprotectin.