**1. Introduction**

Genital infection caused by Chlamydia trachomatis is considered one of the most common sexually transmitted infections in the world. C. trachomatis is an obligate intracellular parasite with a unique intracellular development cycle. The peculiarities of the pathogen itself, the imperfection of the immune response to it, and the characteristic course of the disease determine the difficulties of its diagnosis and treatment.

Chlamydia infection is asymptomatic in most cases, more than 2/3 of women and men. Symptoms of the acute form of the disease (short-term urethritis, moderate discharge) often go unnoticed. This is the reason for the late visit to the doctor and the widespread spread of infection. Without timely and adequate therapy, the infection becomes a chronic persistent form.

Persistent chlamydia infection is widespread and presents the greatest difficulties for doctors. It is associated with a large number of diseases accompanied by chronic inflammation and fibrosis—chronic cervicitis and salpingitis, chronic recurrent urethritis, including "postcoital" urethritis in women, chronic prostatitis, chronic epididymitis, and orchoepididymitis. Clinical manifestations are poorly expressed, or absent altogether, or appear only with exacerbations. As the infection exists, fibrosis processes occur with the formation of adhesions in the appendages of the uterus and pelvis, intrauterine synechiae, and sclerosing processes of the male genital sphere. Pronounced dysfunctional changes in the anti-infective protection system can lead to the translocation of chlamydia from the genitourinary tract to the extra-genital areas of the body. Fibrous changes can hinder the development of the acute phase of inflammation, but lead to infertility in both women (violation of the patency of the fallopian tubes, miscarriage of pregnancy) and men (violations of the morphology and function of sperm), to the formation of chronic pelvic pain syndrome.

Chronic endometritis is also a frequent cause of infertility. Nowadays, it is a widespread disease. It is thought to occur in ¼ of women [1]. Currently, there is no definitive opinion on the role of bacterial factor and chlamydia inclusive in the development and maintenance of chronic endometritis. However, clinical practice gives us some evidence of their important role. Some evidence-based studies show an increase in the frequency of implantation and an improvement in reproductive outcomes in assisted reproductive technology programs after antibiotic therapy [2, 3].

Patients' subjective underestimation of their condition is one of the reasons for the late detection of chlamydia infection. Often, it is diagnosed only when a woman applies for infertility, miscarriage, or other chronic conditions, and men are examined as a partner. As a result, most men and women with chlamydia infection go to the doctor already with the development of deep lesions of the genital area, pronounced adhesive processes, with decompensation of the body's defense mechanisms. The detection of chlamydia infection by routine methods may be difficult at this stage, and it remains unrecognized.

In clinical practice, the physician is faced with a mismatch between the widespread clinical and anatomical manifestation characteristic of chlamydia and its low detectability [4–6]. It can be assumed that this occurs against the background of an increase in the frequency of persistent species C. trachomatis, which develops primarily due to irrational antibiotic therapy [6].
