Human infections caused by Chlamydia trachoma

Chlamydia trachomatis is a bacteria and an intracellular obligatory disease causing organism and belongs to the Genus Chlamydia (is one of the three from this genus).  The bacteria cannot be stained using Gram staining process, but is Gram-negative structurally (Hunt 2009).  There are four biovars (biological variants) of C.trachomatis that causes infection in man (Erbelding, 2009).  These include ones which trachoma, urogential infection, lymphogranuloma venereum, and pneumonia.  The bacteria can survive on a limited range of hosts and infect only certain epithelial cells.  Besides, each of the biovars is divided again into various serotypes (serovars).  The trachoma type has the serovars A, B, Ba and C, the urethritis type has the serovars D  K, the lymphogranuloma venereum type has the serovars LGV1, LGV2  LGV3 (Hunt 2009).

C. trachomatis is an intracellular obligatory parasite that has to depend on the eukaryotic host cell for energy in the form of ATP.  The cell can be cultured only in a cell-based culture system.  C.trachomatis usually causes infection in non-ciliated columnar cells and affects PMN neutrophils and lymphocytes to infiltrate the areas causing fibrotic tissue changes and lymphoid follicle formation.  Once the cell gets destroyed locally and an inflammatory response follows and clinical symptoms occur.  However, once an individual gets infected with Chlamydia trachomatis, there are chances of reinfection, as infection does not confer immunity.  Reinfection may be followed by an inflammatory response and tissue damage.  In individuals suffering from HIV, C trachomatis is known to commonly affect the columnar and the cuboidal epithelium cells of the body (Hunt 2009).

The word Chlamydia comes from the Greek word Chlamys which means Cloak draped around the shoulder referring to the manner in which intracytoplasmic inclusions get draped around the infected nucleus.  It was only until recently has the infection been recognized as a unique identity.  It was only in the year 1957 was the bacteria isolated from embryonic cells and in 1963 from cell cultures.  As the bacteria have a unique developmental cycle it is given a separate taxonomical classification.  The genome of Chlamydia has both DNA and RNA and is about 500 to 1000 kilobase in length.  The bacteria can be differentiated from other by using DNA-based tests.  Usually the bacteria are recognised by the presence of certain monoclonal antibodies (TJ Clark 2009).

C. trachomatis usually colonizes when the sialic acid receptors in the eye, genitals and the pharynx are attached to the bacteria.  Usually the bacteria attach itself to sites that are not accessible by the T-cells and the B-cells.  The C.trachomatis species has a cell wall that can prevent phagolysosome fusion in the phagocytes.  The cell wall of the bacteria contains lipopolysacchride in its outer cell wall making it appear gram negative, but lacks peptiglycan.  However, some bacteria may contain carboxylated sugars in their cell wall.  The outer cell membrane protein is cross-linked with disulphide bonds and contains cysteine-rich proteins, which function as peptigylcans.  The cells can divide easily and can also survive in various treacherous environments (TJ Clark 2009).

There are 2 stages in the life-cycle of the C.trachomatis bacteria, namely the elementary body stage and the reticulate stage.  The elementary body is similar to a spore and is about 0.3 micron in length.  During this stage, phagolysosomal fusion is prevented and hence, the cell can survive.  Once the bacteria find an appropriate host cell, the glycogen that has been synthesized helps to convert the elementary body into the reticulate body (which is the vegetative form that can divide by the process of binary fission).  The incubation period in the host is about 7 to 21 days.  The reticulate body can form elementary bodies that are released by a process known as exocytosis.  Usually about 100 to 1000 elementary bodies are produced by one phagolysosome (TJ Clark 2009).

C. Trachomatis can cause several human infections such as ocular infections, genital infection, pneumonia, arthritis, etc.  About 500 million people each year are affected with ocular infection and about 1 to 2  of these actually become blind.  The infection is seen in many parts of the world including Middle East, Africa, South East Asia, and the Native American populations.  The condition is more common in children and arises from overcrowding and poor sanitation.  The infection is transmitted through infected droplets, contaminated personal items, etc.  The Genital infections caused by C.trachomatis can occur by the biovar trachoma or LGV.  There are common in the US, but are rampant in Africa, South America and Asia.  In the US, about 300 to 500 cases of Chlamydia LGV are recorded each year, mainly due to homosexuality.  Trachoma STD includes about 4 million cases of new infections in the US, and about 50 million new cases throughout the world.  These conditions usually occur in teens and young adults (TJ Clark 2009).

In the UK, the number of cases of Chlamydia infection has been on the rise since the 1990s.  The condition usually get the infection usually have not symptoms (in about 50 of men and 80) of the women.  In 2007, the established cases of Chlamydia were about 121,000, with about two-thirds of the cases affected teenagers and young adults (NHS, 2009).  If the symptoms of Chlamydia infections are not obvious, there are greater chances that the infection detected during the later stages would cause serious complications, resulting in huge costs for the individuals and also the NHS System (SIGN Network 2009).  Chlamydia can present itself as a range of symptoms depending on the site it affects.  Some of the common manifestations of Chlamydia infection include conjunctivitis, scarring of the conjunctiva, ulceration of the corneal blood vessels, blindness, ear infection, peri-hepatitis, Bartholinitis, rhinitis, pneumonia, wheezing, cough, lymphadenopathy, urethritis, proctitis, infertility, epididymitis, prostatis, cervicitis, Pelvic inflammatory disease, pelvic pain, ectopic pregnancy, etc (Hunt 2009).

Most of the Chlamydia infections can be treated with antibiotics.  These drugs can also be given prophylactically in case the individual is at a risk of getting infected.  The two most common antibiotics given for Chlamydia infections are single-dose Azithromycin and multi-dose Doxycycline (for 1-2 weeks) (NHS 2009).  Usually, uncomplicated infections are treated with shorter drug regimens.  For genitourinary tract infections, longer drug durations andor multiple antibiotics may be required (Erbelding 2009).  Less often other antibiotics such as amoxicillin, erythromycin and ofloxacin can be given.  In case of pregnancy alternative forms of antibiotics are given such as erythromycin, Azithromycin and amoxicillin.  Several other strategies can be adopted to help in the prevention of the disease.  Routine screening in risky cases is essential.  Greater information about the signs, symptoms, risks, etc, should be provided to the community.  Screening should be available at lower costs (NHS 2009).  


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