Chlamydia trachomatis, an obligate intracellular human pathogen, is one of three bacterial species in the genus Chlamydia. C. trachomatis is a Gram-Negative bacteria, therefore its cell wall components retain the counter-stain safranin and appear pink under a light microscope. It can appear as either coccoid or rod shape. 
The inclusion bodies of Chlamydia trachomatis were first described in 1942, the Chlamydia trachomatis agent was first cultured in the yolk sacs of eggs by Professor Feifan Tang et al in 1957.
Chlamydial infection. Advances in the diagnostic isolation of Chlamydia, including TRIC agent, from the eye, genital tract, and rectum.
C. trachomatis includes three human biovars:
Many, but not all, C. trachomatis strains have an extrachromosomal plasmid.
In a study released on March 12, 2012 in Nature Genetics, researchers have found that Chlamydia has evolved more actively than was previously thought. Using whole genome sequencing the researchers show that the exchange of DNA between different strains of Chlamydia to form new strains is much more common than expected.
Chlamydia species are readily identified and distinguished from other chlamydial species using DNA-based tests.
Most strains of C. trachomatis are recognized by monoclonal antibodies (mAbs) to epitopes in the VS4 region of MOMP. However, these mAbs may also cross-react with two other Chlamydia species, C. suis and C. muridarum.
C. trachomatis is an obligate intracellular pathogen (i.e. the bacterium lives within human cells) and can cause numerous disease states in both men and women. Both sexes can display urethritis, proctitis (rectal disease and bleeding), trachoma, and infertility. The bacterium can cause prostatitis and epididymitis in men. In women, cervicitis, pelvic inflammatory disease (PID), ectopic pregnancy, and acute or chronic pelvic pain are frequent complications.
C. trachomatis is also an important neonatal pathogen, where it can lead to infections of the eye (trachoma) and pulmonary complications. Chlamydia trachomatis is the single most important infectious agent associated with blindness; approximately 600 million worldwide suffer C. trachomatis eye infections and 20 million are blinded as a result of the infection.
C. trachomatis may be treated with any of several bacteriostatic antibiotics: macrolides (azithromycin, clarithromycin, erythromycin, etc) or tetracyclines (doxycycline, tetracycline, etc).
- Nucleic acid amplification tests (NAAT). These tests find the genetic material (DNA) of chlamydia bacteria. These tests are the most sensitive tests available. That means they are very accurate and that they are very unlikely to have false-negative test results. A polymerase chain reaction (PCR) test is an example of a nucleic acid amplification test. This test can also be done on a urine sample.
- Nucleic acid hybridization tests (DNA probe test). A probe test also finds chlamydia DNA. A probe test is very accurate but is not as sensitive as nucleic acid amplification tests.
- Enzyme-linked immunosorbent assay (ELISA, EIA). This quick test finds substances (chlamydia antigens) that trigger the immune system to fight chlamydia infection.
- Direct fluorescent antibody test (DFA). This quick test also finds chlamydia antigens.
- Chlamydia cell culture. A cell culture is a test that is done that allows the chlamydia bacteria to grow in a vial of cells. The virus attacks the cells and after a set incubation time (48 hours) the vials are stained and viewed on a fluorescent light microscope. This test is more expensive, and the results take longer (two days) than the other tests. The culture must be done in a lab.
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