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Chlamydial Sexually Transmitted Diseases

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  • An intracellular membrane-bound prokaryotic organism, Chlamydia trachomatis is the most common bacterial STI in the US.
  • Transmitted through vaginal, anal, or oral sex; may also occur vertically from mother to infant during vaginal birth
  • Most common bacterial sexually transmitted disease reported to the CDC (1).
  • Majority of cases are asymptomatic, especially in females. Untreated disease can lead to pelvic inflammatory disease (PID), ectopic pregnancy, infertility.
  • System(s) affected: Reproductive

Pregnancy Considerations
Perinatal acquisition may result in neonatal pneumonia and/or conjunctivitis.


  • Mandatory reporting started in 1985, with data showing steady increase in incidence since.
  • 1.4 million reported cases in 2011. Increasing incidence reflects greater screening, improved testing modalities, and better reporting rather than a large increase in disease burden.
  • Swedish new variant chlamydia (nvCT) was first reported in 2006; often produces false-negative tests; largely confined to Nordic countries (2). Sensitive testing of 473 samples from around the US found none of the variants.

  • 457.6/100,000 people in the US in 2011
  • Populations most affected: Young females, particularly those of ethnic minority groups
  • Peak incidence: Age 18–20
  • Predominant sex: Females > Males. Females have >2.5 × higher reported incidence and prevalence than males, but this likely reflects increased testing in females. Increasing use of urine screening may increase screening in males.
  • Minorities bear the highest burden, with infection rates among blacks in >7 × that of whites. Rates higher in larger, more metropolitan areas.
  • Highest prevalence for males is in heterosexual adolescents

Etiology and Pathophysiology

C. trachomatis serotypes D–K

Risk Factors

Risk correlates with:

  • Number of lifetime sexual partners and number of concurrent sexual partners
  • Lack of barrier contraception during sexual intercourse
  • Younger age (highest in females 15–19 years, males 20–24 years)
  • Black/Hispanic/Native American and Alaskan Native ethnicity

General Prevention

  • Populations with prevalence >5% should be screened at least annually (1). Screen if: New or >1 sex partner in past 6 months, attending an adolescent or family-planning clinic or STD or abortion clinic, attending a jail or other detention-center clinic, rectal pain, discharge or tenesmus, testicular pain; test any individual with urethral or cervical discharge.
  • All sexually active women ≤25 years of age should be screened at least yearly, and repeat testing in ∼3months is recommended for those who screen positive, because reinfection rate is high regardless of whether the sexual partner is treated(3)[A].
  • Screening sexually active men ≤25 years is controversial but should be strongly considered in high-risk populations.
  • Annual screening is recommended for men who have sex with men; this may include, as appropriate, rectal nucleic acid amplification test (NAAT) and/or urethral (urine) testing.

Commonly Associated Conditions

  • Females:
    • Pelvic inflammatory disease (PID): ∼10% of women with positive chlamydia screen developed PID within 12 months (4).
    • Infertility and ectopic pregnancies
    • Chronic pelvic pain
    • Mucopurulent cervicitis with cervical edema and propensity to bleed during speculum exam
    • Urethral syndrome (dysuria, frequency, and pyuria in the absence of infection with uropathogen)
    • Arthritis (rare)
    • Spontaneous abortion (5)
  • Males:
    • Epididymitis and nongonococcal urethritis
    • Reiter syndrome (HLA-B27)
    • Proctitis
  • Neonates:
    • Inclusion conjunctivitis (occurs in ∼40% of exposed neonates) (3)
    • Otitis media
    • Pneumonia
    • Pharyngitis
  • Diseases caused by other chlamydial species:
    • Lymphogranuloma venereum: C. trachomatis serotypes L1–L3
    • Trachoma: C. trachomatis serotypes A–C

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