Chlamydia Trachomatis Infection



Chlamydiae are obligate intracellular bacteria responsible for pulmonary infections, ocular trachoma, sexually transmitted diseases, and infections of the genital tract in the pediatric and adult population.

  • The genus Chlamydophila has three species known to affect humans:
    • Chlamydia trachomatis
    • Chlamydophila psittaci
    • Chlamydophila pneumoniae
  • All three species can produce the clinical picture of the so-called atypical or interstitial pneumonia.
  • C. trachomatis can cause afebrile pneumonia in 10–20% of infants born to infected mothers. Infected infants usually present prior to 2 months of age. Up to 50% of patients have a history of inclusion conjunctivitis.
  • C. psittaci is mainly pathogenic for birds and occasionally affects humans, typically causing interstitial pneumonitis with associated fever, headache, malaise, and nausea.
  • C. pneumoniae causes pneumonia, pharyngitis, sinusitis, and bronchitis in humans.

General Prevention

  • Adequate surveillance and treatment of C. trachomatis colonizing the genital tract of pregnant women is the best way of preventing disease in the infant.
  • Annual chlamydia screening for all sexually active women <25 years and for all pregnant women in the first trimester of pregnancy is recommended.
Ocular prophylaxis at birth does not reliably prevent C. trachomatis conjunctivitis or extraocular infection, even if erythromycin ointment is used. Topical treatment alone is not recommended because it does not eradicate the nasopharyngeal colonization.


C. trachomatis

  • There are at least 18 serologically distinct variants with different associations:
    • A–C: trachoma
    • D–K: genital, oculogenital, and perinatal infection
    • L1–L3: lymphogranuloma venereum (LGV)
  • C. trachomatis is the most frequent cause of epididymitis in sexually active young men.
  • Incubation period: 5 to 14 days after delivery for conjunctivitis and 3 to 19 weeks for neonatal pneumonia
  • The possibility of sexual abuse should be considered in older infants and children with vaginal, urethral, or rectal C. trachomatis.


  • This is the most common reportable sexually transmitted infection in the United States. The number of new infections exceeds 1.3 million annually.
  • Most infections occur in 15- to 19-year and 20- to 24-year age groups.
  • C. trachomatis is responsible for neonatal conjunctivitis, trachoma, pneumonia in young infants, genital tract infection, and LGV.
  • Rates of infection in adolescent girls are 15–20%.
  • 23–55% of all cases of nongonococcal urethritis in men are caused by C. trachomatis. Up to 50% of men with gonorrhea may be coinfected with C. trachomatis.
  • C. trachomatis pneumonia usually develops in infected infants <2 months of age (2 weeks to 5 months). The contagiousness of pulmonary disease is unknown but is considered low.
  • 50–75% of the neonates born to infected mothers via vaginal delivery will acquire C. trachomatis. Conjunctivitis may develop in 30–50%.
C. trachomatis infection can occur in infants delivered by cesarean section, even without rupture of amniotic membranes.
  • Pneumonia may develop in up to 30% of infants with nasopharyngeal infection.
  • Ocular trachoma caused by serovars A, B, Ba, and C is the most common cause of preventable blindness in the world but is rare in the United States.
  • Rates among African Americans are 8 times that of Caucasians, followed by American Indians/Alaska natives (4.3 times) and Hispanics (2.7 times).

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