Introduction. Everywhere, about 15% of couples of reproductive age have the problem of infertility, with the male factor being the main cause in 50% of cases. The lack of effective treatment for male infertility is largely due to the multifactorial etiology of this disease. One of these factors is infections of the urogenital tract, the diagnostic search for which requires the development of new methods. Today, next generation sequencing (NGS), using the nucleotide sequence in the 16S rRNA region of the bacterial genome, is the most modern and highly sensitive method for determining the microbiome. Aim: to study and compare the structure of the testicular and urethral microbiota in patients with various types of azoospermia and concomitant varicocele.

Materials and methods. The study included 107 infertile patients with various types of azoospermia, in some cases, with concomitant varicocele, who applied to the Center for Reproductive and Cellular Medicine of the State Budgetary Healthcare Institution of the Children's City Clinical Hospital in Krasnodar, Ministry of Health of the Republic of Krasnodar region. As a result of sample preparation, 31 samples did not meet the quality criteria and were excluded from the study. In all cases, patients underwent micro-TESE (multifocal testicular biopsy), as well as collection of biological material from the urethra. When studying the structure of the microbiome of testicular tissue, amplicons of the bacterial 16S rRNA gene were analyzed using high-throughput next-generation sequencing (NGS). Data were processed using the QIIME program (version 1.9.1).

Results. Comparative characteristics of the structure of the microbiota of the urethra and testicles were carried out using average values in groups, at the level of phyla and families. When comparing the urethral microbiota, a similarity in the species composition of the microbiota was revealed in patients with nonobstructive azoospermia (NOA) and obstructive azoospermia (ОА), while the species composition of the testicular microbiota in patients with ОА is similar to that in patients with varicocele. As a result of data analysis, 6 phyla and 12 families of bacteria were identified that are common to both testicular and urethral tissue. When comparing the frequency of occurrence of these bacteria, differences were identified in the comparison groups.

Conclusions. The microbiota of the urethra in men has a wide taxonomic composition, which has characteristics in infertile patients, caused, in our opinion, by disruption of the GTB, in particular, in patients with varicocele. The structure of the microbiota of testicular tissue has a decrease in species diversity in patients with non-obstructive azoospermia with the dominant Enterobacteriaceae_A family, in contrast to patients with obstructive azoospermia and patients with NOA and concomitant varicocele. The current situation and the discrepancy in scientific publications and expert opinions require further expansion of the range of scientific interdisciplinary research.