Urogenital chlamidiosis is one of the most common illness among sexually transmitted diseases (STD). According to WHO data, around 130 million cases of chlamidiosis are registered yearly, and around 8% of world population are carriers of chlamidias. A sexually transmitted pathogen is Chlamydia trachomatis, which is a non-motile, coccoid, gram-negative intracellular parasite with a diameter of 250-300 nm. Chlamydia takes two forms in the cycle: elementary body and reticulate body. C. trachomatis is able to exit host cells without their lysis.
The course of chlamidiosis is very often (46% in men and 67% in women) asymptomatic or with only minimal symptoms. The latter are almost exclusively non-specific and typical for other STD (vaginal discharge and pain during urination). Acute stage of chlamydia infection lasts only 2 weeks and can be almost unnoticeable. The first symptoms of chlamydiosis disappear quickly even without therapy but the disease could become chronic with periodic reactivations due to the influence of provoking agents. Chronic chlamidiosis could cause infertility both in women and men due to the blockage of the fallopian tubes or chronic prostatitis accordingly.
The diagnostics of C. trachomatis infection is quite complicated due to the life cycle of C. trachomatis. Non-invasive methods of diagnostics are becoming more popular. Detection of bacterial DNA by PCR is the most specific and sensitive (up to 100%) method for diagnostics of active chlamidiosis, but the testing result depends on the specimen collection and preservation. Serologic methods including enzyme linked immunosorbent assay (ELISA) allow determination of the disease stage and its course, which is important at the chronic chlamidiosis that lasts up to many years. ELISA could measure the titres of specific IgM, IgA and IgG.
Specific IgA antibodies could be detected in serum and body secretions, both at the acute and chronic diseases. IgA antibodies appear in serum 10-14 days after the disease onset, which are detectable before IgG appears but at the lower concentrations. Soon after disease onset, secretory IgA could be detected in vaginal and urinary secretions. High titres of IgA could be a marker of chronic infection. Specific IgA have a period of half-life of 5-7 days which could be used for monitoring of therapy success. The 2-3-fold decrease of IgA titres is a marker of successful therapy.
IgG antibodies are detectable from the 3rd week after the disease onset. Their presence reflects a general character of immune response under the acute, chronic or past infection. In the latter case IgG could be detectable at low levels for many years.
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