- Organism
- Chlamydia trachomatis (serotypes D-K cause genital infection; A-C cause trachoma; L1-L3 cause lymphogranuloma venereum)
- Obligate intracellular bacterium (cannot synthesize ATP)
- Elementary body (infectious form) → Reticulate body (replicative form)
- Epidemiology
- Most common bacterial STI in the US
- Highest incidence in sexually active adolescents and young adults (<25 years)
- Clinical Features
- Males:
- Urethritis: dysuria, urethral discharge (often watery/mucoid)
- Epididymitis: unilateral testicular pain, swelling
- Proctitis (in MSM): rectal pain, discharge, bleeding
- Females:
- Often asymptomatic (70-80%)
- Cervicitis: mucopurulent discharge, friable cervix
- Urethritis: dysuria, frequency
- Pelvic Inflammatory Disease (PID): lower abdominal pain, cervical motion tenderness, fever
- Complications:
- Females: PID → chronic pelvic pain, ectopic pregnancy, infertility (tubal scarring)
- Males: Epididymitis, reactive arthritis
- Fitz-Hugh-Curtis syndrome: perihepatitis with RUQ pain (“violin string” adhesions)
- Reactive arthritis (Reiter syndrome): triad of urethritis, conjunctivitis, arthritis (“can’t see, can’t pee, can’t climb a tree”)
- Neonatal:
- Conjunctivitis (5-14 days after birth)
- Pneumonia (1-3 months): staccato cough, tachypnea, bilateral interstitial infiltrates
- Diagnostics
- Nucleic Acid Amplification Test (NAAT): test of choice (urine or swab)
- High sensitivity and specificity
- Screen sexually active females <25 years annually
- Treatment
- First-line: Doxycycline 100 mg PO BID × 7 days
- Alternative: Azithromycin 1 g PO single dose (preferred in pregnancy, but doxycycline more effective)
- Treat sexual partners from past 60 days
- Abstain from sex for 7 days after treatment completion
- Pregnancy: Azithromycin 1 g PO single dose (doxycycline contraindicated)
- Key Associations
- Co-infection with Neisseria gonorrhoeae common (treat both empirically in PID)
- Lymphogranuloma venereum (LGV): serotypes L1-L3 cause painful inguinal lymphadenopathy with groove sign