Chlamydia trachomatis

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Chapter 218 Chlamydia trachomatis

Margaret R. Hammerschlag

Chlamydia trachomatis is subdivided into 2 biovars: lymphogranuloma venereum (LGV) and trachoma, which is the agent of human oculogenital diseases other than LGV. Although the strains of both biovars have almost complete DNA homology, they differ in growth characteristics and virulence in tissue culture and animals. In developed countries, C. trachomatis is the most prevalent sexually transmitted disease, causing urethritis in men, cervicitis and salpingitis in women, and conjunctivitis and pneumonia in infants.

218.1 Trachoma

Margaret R. Hammerschlag

Trachoma is the most important preventable cause of blindness in the world. It is caused primarily by the A, B, Ba, and C serotypes of C. trachomatis. It is endemic in the Middle East and Southeast Asia and among Navajo Indians in the southwestern USA. In areas that are endemic for trachoma, such as Egypt, genital chlamydial infection is caused by the serotypes responsible for oculogenital disease: D, E, F, G, H, I, J, and K. The disease is spread from eye to eye. Flies are a common vector.

Trachoma begins as a follicular conjunctivitis, usually in early childhood. The follicles heal, leading to conjunctival scarring that can result in an entropion, with the eyelid turning inward so that the lashes abrade the cornea. It is the corneal ulceration secondary to the constant trauma that leads to scarring and blindness. Bacterial superinfection can also contribute to scarring. Blindness occurs years after the active disease.

Trachoma can be diagnosed clinically. The World Health Organization (WHO) suggests that at least 2 of 4 criteria must be present for a diagnosis of trachoma: lymphoid follicles on the upper tarsal conjunctivae, typical conjunctival scarring, vascular pannus, and limbal follicles. The diagnosis is confirmed by culture or staining tests for C. trachomatis performed during the active stage of disease. Serologic tests are not helpful clinically because of the long duration of the disease and the high seroprevalence in endemic populations.

Poverty and lack of sanitation are important factors in the spread of trachoma. As socioeconomic conditions improve, the incidence of the disease decreases substantially. Endemic trachoma has been controlled in most instances by administering topical tetracyclines (or, rarely, erythromycin ointment) daily for periods of 6-10 wk or intermittently over a 6-mo period. Oral doxycycline is effective but is contraindicated in children <8 yr of age. Oral erythromycin requires frequent dosing, which is impractical in the control of endemic trachoma. Several studies have reported that 1-6 doses of oral azithromycin are equivalent to 30 days of treatment with topical oxytetracycline/polymyxin ointment. The WHO recommends single-dose azithromycin (20 mg/kg, maximum 1g) for the treatment of trachoma in children. A study from Tanzania demonstrated that mass treatment with a single dose of azithromycin to all the residents of a village dramatically reduced the prevalence and intensity of infection. This effect continued for 2 years after treatment, probably by interrupting the transmission of ocular C. trachomatis infection.

Bibliography

Chidambaram JD, Alemayehu W, Melese M, et al. Effect of a single mass antibiotic distribution on the prevalence of infectious trachoma. JAMA. 2006;295:1142-1146.

Grassley NC, Ward ME, Ferris S, et al. The natural history of trachoma infection and disease in a Gambian cohort with frequent follow-up. PloS Negl Trop Dis. 2008;2:e341.

House JI, Ayele B, Porco TC, et al. Assessment of herd protection against trachoma due to repeated mass antibiotic distributions: a cluster randomized trial. Lancet. 2009;373:1111-1118.

Nieuwenhuis RF, Ossewaarde JM, Götz HM, et al. Resurgence of lymphogranuloma venereum in Western Europe: an outbreak of Chlamydia trachomatis serovar L2 proctitis in the Netherlands among men who have had sex with men. Clin Infect Dis. 2004;39:996-1003.

Solomon AW, Peeling RW, Foster A, et al. Diagnosis and assessment of trachoma. Clin Microbiol Rev. 2004;17:982-1011.

Taylor HR. Elimination of blinding trachoma revolves around children. Lancet. 2009;373:1061-1063.

218.2 Genital Tract Infections

Margaret R. Hammerschlag

Epidemiology

There are an estimated 3 million new cases of chlamydial sexually transmitted infections each year in the USA. C. trachomatis is a major cause of epididymitis and is the cause of 23-55% of all cases of nongonococcal urethritis, although the proportion of chlamydial nongonococcal urethritis has been gradually declining. As many as 50% of men with gonorrhea may be co-infected with C. trachomatis. The prevalence of chlamydial cervicitis among sexually active women is 2-35%. Rates of infection among girls 15-19 yr of age exceed 20% in many urban populations but can be as high as 15% in suburban populations as well.

Children who have been sexually abused can acquire anogenital C. trachomatis infection, which is usually asymptomatic. Culture is the only method that should be used for diagnosis of C. trachomatis from these sites when a prepubertal child is being tested for suspected sexual abuse. However, because perinatally acquired rectal and vaginal C. trachomatis infections can persist for ≥3 years, the detection of C. trachomatis in the vagina or rectum of a young child is not absolute evidence of sexual abuse.

Clinical Manifestations

The trachoma biovar of C. trachomatis causes a spectrum of disease in sexually active adolescents and adults. Up to 75% of women with C. trachomatis have no symptoms of infection. C. trachomatis can cause urethritis (acute urethral syndrome), epididymitis, cervicitis, salpingitis, proctitis, and pelvic inflammatory disease. The symptoms of chlamydial genital tract infections are less acute than those of gonorrhea, consisting of a discharge that is usually mucoid rather than purulent. Asymptomatic urethral infection is common in sexually active men. Autoinoculation from the genital tract to the eyes can lead to concomitant inclusion conjunctivitis.

Diagnosis

Definitive diagnosis of genital chlamydial infection is accomplished by isolation of the organism in tissue culture and confirmed by microscopic identification of the characteristic inclusions using fluorescent antibody staining in culture specimens obtained from the urethra in men and the endocervix in women. Care should be taken to obtain epithelial cells, not only discharge. C. trachomatis can be cultured in cycloheximide-treated HeLa, McCoy, and HEp-2 cells. Chlamydia culture has been further defined by the Centers for Disease Control and Prevention (CDC) as isolation of the organism in tissue culture and as confirmation of the characteristic intracytoplasmic inclusions by fluorescent antibody staining.

Alternatively, a nonculture method, specifically a nucleic acid amplification test (NAAT) can be used. These tests have high sensitivity, perhaps even detecting 10-20% greater than culture, while retaining high specificity. Three Food and Drug Administration (FDA)-approved NAATs are comercially available for detecting C. trachomatis: polymerase chain reaction (PCR; Amplicor Chlamydia test, Roche Molecular Diagnostics, Nutley, NJ), strand displacement amplification (SDA; ProbeTec, BD Diagnostic Systems, Sparks, MD), and transcription-mediated amplification (TMA; Amp CT, Gen-Probe, San Diego, CA). PCR and SDA are DNA amplification tests that use primers that target gene sequences on the cryptogenic C. trachomatis

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