DESCRIPTION

• Chlamydia trachomatis is the most common bacterial sexually transmitted infection (STI) in the United States.
• Transmitted through vaginal, anal, or oral sex and vertically during vaginal delivery
• Most cases are asymptomatic. Untreated disease can lead to pelvic inflammatory disease (PID), ectopic pregnancy, and infertility.

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

EPIDEMIOLOGY

ETIOLOGY AND PATHOPHYSIOLOGY

C. trachomatis serotypes D to K are associated with genital tract infections. Chlamydia is an obligate intracellular organism and has a biphasic life cycle. Chlamydia derives from the Greek word for “cloak.” Its extracellular elementary body (EB) is metabolically inactive and infectious. Once taken up by host cell (columnar epithelium of the genital tract), the EB prevents lysosomal phagocytosis and transforms to reticulate body (RB) which uses energy from host cell to synthesize RNA, DNA, and proteins. EBs are released to infect neighboring cells or to infect other individuals through sexual contact.

RISK FACTORS

Risk correlates with:

• Number of lifetime and concurrent sexual partners
• Lack of barrier contraception during intercourse
• Black/Hispanic/Native American and Alaskan Native ethnicity
• Men who have sex with men (MSM) may be at higher risk for rectal and pharyngeal chlamydia; Consider testing with NAAT when appropriate (1).

GENERAL PREVENTION

• Screening recommended if with new or >1 sex partner in past 6 months. Screen if with rectal pain, discharge, tenesmus, or testicular pain and test all individuals with urethral or cervical discharge.
• All sexually active women ≤25 years of age should be screened at least yearly. Repeat testing in ~3 months is recommended for those who screen positive because reinfection rate is high regardless of whether the sexual partner is treated or not (2)[A].
• Consider screening sexually active men ≤25 years of age particularly in high-risk populations.
• Screen high-risk MSM annually with genital and extragenital screening (3)[A].
• NAAT is the preferred screening test in all circumstances except child sexual abuse involving boys or rectal/oropharyngeal testing in prepubescent girls. For these situations, culture and susceptibility testing is preferred (3)[A].
• Acceptable to screen women for chlamydia on same day as intrauterine device (IUD) insertion—treat if positive (no need to remove IUD in this circumstance).
• Doxycycline postexposure prophylaxis (“Doxy-PEP”) is an emerging prevention strategy for chlamydia, syphilis, and possibly gonorrhea, currently best studied in MSM and transgender women with a history of bacterial STI within the past year.

COMMONLY ASSOCIATED CONDITIONS

• Individuals with female anatomy
  • PID: ~10% develop PID within 12 months if untreated.
  • Infertility, ectopic pregnancy
  • Chronic pelvic pain
  • Urethral syndrome (dysuria, frequency, and pyuria in the absence of infection)
• Individuals with male anatomy
  • Epididymitis and nongonococcal urethritis
  • Reiter syndrome (HLA-B27)
  • Proctitis
• Neonates
  • Inclusion conjunctivitis (occurs in ~40% of exposed neonates)
• Diseases caused by other chlamydial species
  • Lymphogranuloma venereum (LGV): C. trachomatis serotypes L1 to L3
  • Trachoma: C. trachomatis serotypes A to C