Pathogenesis
The pathogenesis of C. trachomatis infections has not been clearly defined. Chlamydiae are obligate intracellular parasites, and disease appears to result from both the destruction of cells during the growth cycle and the body’s immune response to the infection producing inflammation.

Clinical Syndromes
Uncomplicated infections include asymptomatic and symptomatic urethritis in men and women. In men, 20 to 50% of those with gonococcal urethritis are also infected with Chlamydia. Chlamydia is responsible for 23 to 55% of nongonococcal urethritis in men, with higher rates among young boys. Endocervicitis is the most common clinical manifestation of infection in sexually active female adolescents. Pelvic inflammatory disease presents as the most serious complication of endocervical infection, including a subclinical form that lacks the typical symptoms, which may also lead to infertility. An overview of syndromes, diagnosis, and treatment is found in

Tables 3-16 and

3-17.

C. trachomatis is the most common cause of nongonococcal urethritis (NGU) in men. Men with NGU may present with discharge and dysuria. The infection is identified through contact tracing from a chlamydial-positive partner or often by screening of symptomatic men. Among women, 50% or more of chlamydial lower genital infections are asymptomatic. An uncomplicated endocervicitis can be associated with the clinical signs consistent with mucopurulent cervicitis (MCP), which presents with a yellow endocervical discharge on a swab sample or by identification of increased polymorphonuclear cells on a Gram stain from the discharge (more than 10-30 per high-power field).

Although it is asymptomatic in many young women, chlamydial cervicitis is sometimes accompanied by abnormal vaginal discharge and abnormal vaginal bleeding, especially after intercourse. Chlamydia has been identified in from 9 to 51% of MPC cases, and the gonococcus is also responsible for some cases as well. However, MPC is not a sensitive indicator of infection because most women with either chlamydial or gonorrheal endocervical infection do not have MPC. Diagnosis by direct testing for Chlamydia, when possible, is encouraged (

Table 3-16). Candida albicans, Trichomonas vaginalis, human papillomavirus, and herpes simplex virus can also produce urethritis in men and women as well as endocervicitis in women.

Diagnosis and Treatment
There are a number of situations such as NGU, PID, epididymitis, and confirmed gonococcal infection (5 to 30% of men and 25 to 50% of women with gonorrhea have concurrent chlamydia) that are associated frequently with chlamydia infections and necessitate immediate “presumptive” treatment to alleviate symptoms and to prevent complications and further transmission to partners. However, chlamydia testing and partner tracing and treatment should still be undertaken when possible. Testing for chlamydia is performed by using either the traditional “gold standard” - the cell culture - or the newer nonculture techniques. Although cell culture is being surpassed by nonculture techniques, the following conditions warrant the continued use of cell culture as the test of choice because nonculture methods have not been developed, have been inadequately tested, or yield poor performance profiles in these situations: urethral and rectal specimens in men and women and vaginal specimens in prepubertal girls.

Currently available tests for Chlamydia include the direct fluorescent antibody (DFA) test, the enzyme immunoassay (EIA) test, the DNA probe test, the rapid chlamydia test, and the leukocyte esterase dipstick test (LET). Except for the MicroTrak DFA (Syva) test and the Chlamydiazyme EIA (Abbott) test, evaluation by available tests is limited. Quality assurance is essential to the performance of any tests, especially the nonculture techniques, where false-  positive results can lead to adverse psychosocial outcomes for the patient and partner. It is therefore essential for the clinician to know the performance capabilities of both the test and the laboratory being employed.

There had been increased interest in evaluation of the nonculture test on urine specimens. The Chlamydia-specific tests, such as the currently available EIA and DNA probe tests, show promise in their ability to detect Chlamydia in a urine specimen. More recently the new technologies—including the polymerase chain reaction (PCR) and the ligase chain reaction (LCR) with their capacity to amplify Chlamydia DNA in specimens—have also been applied to urine specimens with early success. Of interest to the primary-care clinician is the ability to screen asymptomatic adolescent boys with the nonspecific LET applied to the first-void urine specimen (first 10 to 15 mL voided into premarked container) for urethritis, which is most frequently caused by chlamydia or gonorrhea. Because the sensitivity of the LET in screening for chlamydia and gonorrhea is 46 to 100% (it is a nonspecific indicator of the presence of polymorphonuclear cells), it is necessary to follow up all positive LETs with more specific gonorrhea and chlamydial tests (eg, EIAs, DFA). Data are insufficient to support the use of the LET to screen young women for chlamydia. The treatment protocols are outlined in

Table 3-17.