Background Information

Chlamydia trachomatis

Chlamydia trachomatis is a sexually transmitted parasitic bacterium. The word Chlamys is Greek for cloak (draped around the shoulder) and describes the site of the intracytoplasmatic inclusions around the nucleus of infected cells. The bacterium cannot synthesize its own ATP and contains both RNA and DNA. Colonization of Chlamydia trachomatis begins with attachment to sialic acid receptors on the eye, throat or genitalia; it persists at body sites that are inaccessible to phagocytes, T- and B-cells. It only infects humans and 15 subtypes are known i.e. A and C, D and K and L1, L2 and L3. Its life cycle consists of two stages: elementary body and reticulate body. The elementary body induces its own endocytosis upon exposure to the target cells. Once inside the endosome, the elementary body germinates into the reticulate body and starts dividing at approximately 2-3 hours per generation. The reticulate body transforms back to the elementary form after division and is released from the cell by exocytosis. One phagolysosome produces 100-1000 elementary bodies.

The number of people with sexually transmitted chlamydial infections is estimated at one in seven under the age of 16 and one in ten in young women. In the western world there are roughly four million cases annually, most occurring in men and women under the age of 25. Transmission is through infected secretions only and infects mucosal membranes of the cervix, rectum, urethra, throat and conjunctiva; the disease symptoms are variable. In 75% of women and 25% of men, symptoms of infection are absent, hence not diagnosed. Others may experience a variety of symptoms such as vaginal secretions, lower abdominal pain and urethritis. In infected women, also without symptoms, ascending chlamydial infection can lead to tubo-ovarian or pelvic abscesses, infertility, chronic pelvic pain and ectopic pregnancy. In men, it can lead to epididymitis, narrowing or blocking of the urethra, sterility scrotal abscesses and constipation. The types responsible for genital tract infections (D and K) can also cause conjunctivitis. In newborn, infection takes places during the passage through an infected birth channel and may result in conjunctivitis. Types L1, L2 and L3 are responsible for lymphogranuloma venerum. The most devastating effect of Chlamydia trachomatis infection is trachoma, a chronic follicular conjunctivitis which is estimated to cause 6 million cases of blindness every year. In some African countries, 40% of the children are affected. Fortunately, Chlamydia infections can be cured provided that a diagnosis is made.

Several diagnostic tests are available, culture and non-culture test. Culture tests have the disadvantage that it takes 3-7 days requires special transport media, technical equipment and is subject to contamination. Certain non-culture tests are not specific and false positive results occur. Similarly, antibody tests can cross-react with non chlamydial species. ISH in contrast is highly specific due to the nature of specific hybridization.

PanPath's labeled probe for Chlamydia trachomatis targets 7.2 Kb plasmid and shows no cross-hybridization with other microorganisms provided that the hybridization conditions as laid out in the protocol are strictly followed.