A 16-year-old girl presents to clinic with a complaint of vaginal discharge. She has only one sexual partner but is unsure if her partner may have had other sexual contacts. On physical examination, there is ectopy and some mucoid discharge (Figure 79-1). The cervix bled easily while obtaining discharge and cells for a wet mount and genetic probe test. The wet mount showed many white blood cells (WBCs) but no visible pathogens. The patient was treated with 1 g of azithromycin taken in front of a clinic nurse. She was tested for HIV, syphilis, Trichomonas, GC, and Chlamydia and given a follow-up appointment in 1 week. The genetic probe test was positive for Chlamydia and all the other examinations were negative. This information was given to the patient on her return visit and safe sex was discussed.

Chlamydia trachomatis causes genital infections that can result in pelvic inflammatory disease (PID), ectopic pregnancy, and infertility. Asymptomatic infection is common among both men and women so health care providers must rely on screening tests to detect disease. The Centers for Disease Control and Prevention (CDC) recommends annual screening of all sexually active women ages 25 years and younger, and of older women with risk factors, such as having a new sex partner or multiple sex partners.¹

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  A very common STD, Chlamydia is the most frequently reported infectious disease in the US (excluding human papillomavirus [HPV]).¹ An estimated 1.2 million cases are reported to the CDC annually in the US.²

  
  
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  The World Health Organization (WHO) estimates there are 140 million cases of Chlamydia trachomatis infection worldwide every year.³

  
  
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  The CDC estimates screening and treatment programs can be conducted at an annual cost of $175 million. Every dollar spent on screening and treatment saves $12 in complications that result from untreated Chlamydia.⁴

  
  
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  It is common among sexually active adolescents and young adults.⁵ As many as 1 in 10 adolescent girls tested for Chlamydia is infected. Based on reports to the CDC provided by states that collect age-specific data, teenage girls have the highest rates of chlamydial infection. In these states, 15- to 19-year-old girls represent 46 percent of infections and 20- to 24-year-old women represent another 33 percent.⁴

  
  
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  Cross-sectional data from the 2003-2004 US National Health and Nutrition Examination Survey (NHANES) shows 4 percent of female adolescents (aged 14 to 19 years) had laboratory evidence of infection with Chlamydia trachomatis.⁶

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  C. trachomatis is a small Gram-negative bacterium with unique biologic properties among living organisms. Chlamydia is an obligate intracellular parasite that has a distinct life-cycle consisting of two major phases: The small elementary bodies attach and penetrate into cells, and the metabolically active reticulate bodies that form large inclusions within cells.

  
  
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  It has a long growth cycle, which explains why extended courses of treatment are often necessary. Immunity to infection is not long-lived, so reinfection or persistent infection is common.

  
  
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  The infection may be asymptomatic and the onset often indolent. Symptoms of infection when present in women are most commonly abnormal vaginal discharge, vaginal bleeding (including after intercourse), and dysuria. Only 2 to 4 percent of infected men reported any symptoms.⁷

  
  
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  It can cause cervicitis, endometritis, PID, infertility, perihepatitis (Fitz-Hugh-Curtis syndrome) urethritis, and epididymitis. It may produce poor neonatal outcomes including premature rupture of membranes, preterm labor, low birth weight, and infant death, conjunctivitis, and pediatric pneumonia.⁸ Of exposed babies, 50 percent develop conjunctivitis and 10 to 16 percent develop pneumonia.¹ Perinatal Chlamydia is the leading cause of infectious blindness in the world, which is particularly worrisome since adolescents are at increased risk for infection and have more barriers to health care screening.⁹

  
  
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  Chlamydia infections may lead to reactive arthritis, which presents with arthritis, conjunctivitis, and urethritis. Past or ongoing C. trachomatis infection may be a risk factor for ovarian cancer.^10,11

  
  
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  Up to 40 percent of women with untreated Chlamydia will develop PID. Undiagnosed PID caused by Chlamydia is common. Of those with PID, 20 percent will become infertile; 18 percent will experience debilitating, chronic pelvic pain; and 9 percent will have a life-threatening tubal pregnancy. Tubal pregnancy is the leading cause of first-trimester, pregnancy-related deaths in American women.⁴

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  Adolescents and young adults.

  
  
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  Nonwhite populations.

  
  
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  Multiple and new sexual partners.

  
  
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  Poor socioeconomic conditions.

  
  
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  Single marital status.

  
  
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  Nonbarrier contraceptive use.

  
  
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  History of prior STD.

Clinical Features

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  The cervix is inflamed, friable, and may bleed easily with manipulation. The cervix may show ectopy (columnar cells on the ectocervix). The discharge is usually mucoid or mucopurulent (Figure 79-1 to 79-3).⁸

  
  
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  Persons who have receptive anal intercourse can acquire a rectal infection, which presents as anal pain, discharge, or bleeding. Persons who engage in oral sex can acquire a pharyngeal infection, which may present as an irritated throat. ⁸

  
  
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  Swab test—A white cotton-tip applicator is placed in the endocervical canal and removed to view. A visible mucopurulent discharge constitutes a positive swab test for Chlamydia (Figure 79-4). This is not specific for Chlamydia as other genital infections can cause a mucopurulent discharge, and is not recommended for diagnosis.