Chlamydia trachomatis is an obligate intracellular pathogen, which is now recognized as the most prevalent sexually transmitted bacteria in the world. Genital infection in women is primarily localized to the endocervix, causing a clinical syndrome of mucopurulent cervicitis. C. trachomatis is a member of the family chlamydiaceae. The major disease symptoms associated with C. trachomatis infection are caused not by direct pathogen activity, but rather by the host immune response to infection. The conventional view holds that manifestations of chlamydial diseases result from classical delayed-type hypersensitivity (DTH) reactions. C. trachomatis infection can also directly destroy infected genital epithelial cells during replication. An alternate growth mode of chlamydia, commonly referred to as persistent growth, has also been observed in vitro. Transmission of C. trachomatis infection from mother to infant may also occur via exposure to intrauterine infection during late pregnancy.