Chlamydiae comprises three species: Chlamydia trachomatis and Chlamydia pneumoniae, primarily human pathogens, and Chlamydia psittaci, primarily an animal pathogen. As they are unable to synthesize ATP, they are obligate intracellular parasites.The replicative cycle of the chlamydiae lasts approximately 48-72 hours and begins with the attachment of an infectious particle, an “elementary body”, to the surface of the susceptible cell. The elementary body enters the cell in a phagocytic vesicle, becomes the reticulate (or initial) body, i.e. the metabolically active replicating form. Within the membrane-bound vacuole, the reticulate body reproduces by binary fission and then “condense” to form elementary bodies. When ready, the vesicle ruptures and releases elementary bodies to infect new cells.Chlamydial infections are the most common sexually transmitted disease. Chlamydia trachomatis is known to cause urethritis, epididymitis, proctitis, cervicitis, pelvic inflammatory disease, infant pneumonia, and conjunctivitis. As these symptoms are common to many diseases, diagnosis is needed for prompt and accurate treatment. However, chlamydial infections are often asymptomatic.Traditionally, chlamydial infection has been diagnosed by detection of chlamydial inclusions in tissue culture cells. However, cell culture methods for isolating Chlamydia are therefore not routinely performed by many laboratories. Direct antigen detection techniques such as Antigen EIA methods offer a cost-effective alternative to culture (see MicroTrak 8H709UL). Chlamydial antigen extracted from urethral, endocervical, and ocular swabs, or from cellular material pelletted from urine specimens can be detected in less than three hours; furthermore, the test is not dependent on having viable organisms, which minimizes the need for the special transport and storage conditions. The application of Antigen EIA for male urine specimens allows testing of males by a non-invasive procedure.The MicroTrak® Direct Specimen Test can detect and resolve elementary bodies in direct patient specimens, this test provides a simple, rapid procedure for the diagnosis of chlamydial infection.