190.1 🎓 醫學生版

190.1.0.1 📌 一頁重點

• 菌: Chlamydia trachomatis — obligate intracellular gram - bacterium; 2-form lifecycle (elementary body EB infectious + reticulate body RB replicative)
• Serotypes (15):
  • A, B, Ba, C: trachoma (blinding eye disease)
  • D-K: genital + neonatal infection (most common)
  • L1, L2, L3: LGV (Lymphogranuloma venereum) — invasive STD with lymphadenopathy
• 臨床 Forms:

Form	Serotypes	臨床
Trachoma	A-C	Chronic follicular conjunctivitis → scarring → trichiasis → blindness
Adult inclusion conjunctivitis	D-K	Mucopurulent conjunctivitis (sexual contact transmission)
Urethritis (♂)	D-K	NGU, often asymptomatic
Cervicitis (♀)	D-K	Often asymptomatic; mucopurulent discharge
PID (♀)	D-K	#1 cause of preventable infertility globally
Fitz-Hugh-Curtis	D-K	Perihepatitis (RUQ pain + PID)
Reactive arthritis (Reiter)	D-K	HLA-B27, post-STD
Neonatal	D-K	Inclusion conjunctivitis (5-12d), pneumonia (2-12 wk)
LGV	L1-3	Painless ulcer → tender suppurative inguinal LAP (“groove sign”); proctitis MSM

• Dx:
  • NAAT (PCR) — gold standard; urine (♂), vaginal/endocervical (♀), rectal, pharyngeal
  • 細胞學 (Giemsa) for trachoma in resource-limited
  • LGV: NAAT + genotype identification
• Treatment:
  • Genital (uncomplicated): Doxycycline 100 mg PO bid × 7d (preferred 2021 CDC update, better cure than azithromycin)
  • Azithromycin 1 g PO × 1 alt (pregnancy preferred — doxy avoided)
  • LGV: doxycycline 100 bid × 21d
  • PID: ceftriaxone + doxy + metronidazole × 14d
  • Neonatal: erythromycin 14d
  • Trachoma: azithromycin 20 mg/kg PO × 1 (SAFE strategy mass drug administration)
• Co-screen: HIV + syphilis + gonorrhea + HBV; partner notification

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190.1.0.2 1️⃣ 細菌學 + Lifecycle

• Obligate intracellular gram -
• Cannot make ATP — energy parasite (host ATP)
• 2-form lifecycle:
  • Elementary body (EB) — infectious, extracellular, metabolically inactive
  • Reticulate body (RB) — intracellular, replicative
• Inclusion in cytoplasm visible on stain (Giemsa)

190.1.0.2.1 15 Serotypes (Serovars)

• A, B, Ba, C — Trachoma (ocular, transmitted by fly + contaminated water in tropics)
• D, E, F, G, H, I, J, K — Genital + neonatal (sexual + vertical)
• L1, L2, L2b, L3 — LGV (more invasive, lymphatic tropism)

190.1.0.2.2 LGV Serotypes Special

• L2b — MSM proctitis outbreaks (Europe, USA, since 2003)

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190.1.0.3 2️⃣ Trachoma (Serotypes A-C)

190.1.0.3.1 流行病學

• Leading infectious cause of blindness globally (~ 1.9 million visually impaired)
• Africa, Middle East, S Asia, Latin America (hot dry regions)
• Trachoma fly (Musca sorbens) — vectors via eye discharge
• Children with eye discharge most infectious
• Active follicular conjunctivitis → repeated infections → conjunctival scarring → eyelid inversion (entropion) → eyelashes scratch cornea (trichiasis) → opacity → blindness

190.1.0.3.2 WHO SAFE Strategy

• Surgery (for trichiasis)
• Antibiotics (mass azithromycin 20 mg/kg × 1)
• Facial cleanliness
• Environmental improvement (water, sanitation)

190.1.0.3.3 Treatment

• Azithromycin 20 mg/kg PO × 1 (community mass administration)
• Tetracycline 1% eye ointment 6 wk (alternative)
• Surgery for trichiasis (entropion)

190.1.0.3.4 Goals

• WHO global elimination as public health problem by 2030
• 17 countries certified by 2024 (Ghana, Iran, Mexico, etc.)

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190.1.0.4 3️⃣ Genital Chlamydia (Serotypes D-K)

190.1.0.4.1 流行病學

• #1 reportable STI globally
• USA: 2 million cases/yr (likely under-diagnosed)
• ~ 50% asymptomatic in both sexes
• 青少年 + young adult main
• Co-infection with gonorrhea common (treat both empirically)

190.1.0.4.2 A. Male — Urethritis

• NGU = non-gonococcal urethritis
• Mucoid / mucopurulent discharge, dysuria
• 30-50% asymptomatic (carry + transmit)
• Complication: epididymitis, prostatitis

190.1.0.4.3 B. Female — Cervicitis + PID

• Cervicitis: mucopurulent discharge, friable cervix, post-coital bleeding; often asymptomatic
• PID: ascending infection
  • Fever, lower abdominal pain, dyspareunia, abnormal discharge
  • Cervical motion tenderness, adnexal tenderness
  • Endometritis, salpingitis, tubo-ovarian abscess
  • Long-term: infertility (silent salpingitis), ectopic pregnancy, chronic pelvic pain
• Fitz-Hugh-Curtis (perihepatitis — RUQ pain, “violin string” adhesions on laparoscopy)

190.1.0.4.4 C. Pharyngeal / Rectal

• MSM, oral / anal sex
• Often asymptomatic
• Proctitis with discharge, tenesmus

190.1.0.4.5 D. Reactive Arthritis (Reiter Syndrome)

• HLA-B27 associated
• 1-4 wk post-infection
• Triad: arthritis (asymmetric oligoarticular lower extremity) + conjunctivitis/uveitis + urethritis
• Self-limited weeks-months but can be chronic

190.1.0.4.6 E. Neonatal (Vertical Transmission)

• Inclusion conjunctivitis (5-12d post-delivery) — mucopurulent, milder than gonococcal
• Pneumonia (2-12 wk) — staccato cough, afebrile, eosinophilia
• Vertical transmission rate 30-50% if mother infected at birth
• Routine maternal screening + treatment prevents

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190.1.0.5 4️⃣ LGV (Lymphogranuloma Venereum) — Serotypes L1-L3

190.1.0.5.1 Epidemiology

• Historically endemic tropics (S America, Africa, SE Asia)
• 2003+ Europe + USA + Canada outbreaks in MSM — proctitis presentation (L2b serotype)

190.1.0.5.2 Clinical 3 Stages

190.1.0.5.2.1 Primary (3-30 d)

• Small painless ulcer / papule at site of inoculation (genital, anal, oral)
• Often missed

190.1.0.5.2.2 Secondary (Inguinal Syndrome) (Weeks-Months)

• Tender suppurative inguinal lymphadenopathy (bubo)
• “Groove sign” — bubo above and below inguinal ligament
• Constitutional sx
• Can rupture and drain

190.1.0.5.2.3 Tertiary (Anogenital Syndrome) (Months-Years)

• Genital lymphedema (elephantiasis genitalia, “esthiomene”)
• Rectal strictures, fistulas
• Chronic ulceration

190.1.0.5.3 MSM Proctitis (Modern Presentation)

• L2b serotype
• Severe rectal pain, bleeding, tenesmus, discharge
• Mimics inflammatory bowel disease
• Rectal NAAT + genotype

190.1.0.5.4 Treatment

• Doxycycline 100 mg PO bid × 21d
• Alt: azithromycin 1 g/wk × 3 wk, erythromycin
• Drain fluctuant bubo

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190.1.0.6 5️⃣ 診斷

190.1.0.6.1 A. NAAT (Nucleic Acid Amplification Test)

• Gold standard — high sensitivity + specificity
• Specimens: urine (♂), vaginal self-swab / endocervical (♀), rectal, pharyngeal, conjunctival
• Often combined with gonorrhea NAAT
• Same-sample testing for both

190.1.0.6.2 B. Genotyping (LGV Suspicion)

• NAAT-positive + clinical features of LGV (proctitis MSM, bubo)
• Confirm L1/L2/L3 (PCR or culture-based)
• Public health labs

190.1.0.6.3 C. Cell Culture

• Specialty labs
• Allows AST (rare clinical need)
• Tissue culture inclusion + Giemsa staining

190.1.0.6.4 D. Tissue / Lesion

• Biopsy for LGV bubo
• Conjunctival smear (Giemsa) for trachoma — historical

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190.1.0.7 6️⃣ Treatment (2021 CDC Update)

190.1.0.7.1 Genital Uncomplicated

• Doxycycline 100 mg PO bid × 7d (preferred — 2021 CDC update, better cure rates 97% vs azithro 84%)
• Azithromycin 1 g PO × 1 (alt; preferred in pregnancy + adherence issues)
• Levofloxacin 500 mg PO qd × 7d (alt)

190.1.0.7.2 Why Doxycycline Preferred Now

• 2021 CDC update — doxy superior in rectal infection particularly
• Rectal infection up to 30% MSM
• Azithro failure higher (LGV serotypes, increased resistance suggestions)

190.1.0.7.3 Pregnancy

• Azithromycin 1 g PO × 1 (preferred — doxy contraindicated)
• Amoxicillin 500 mg PO tid × 7d (alt)
• Erythromycin 14d (alt)

190.1.0.7.4 LGV

• Doxycycline 100 mg PO bid × 21d

190.1.0.7.5 PID (Outpatient)

• Ceftriaxone 500 mg IM × 1 + doxycycline 100 bid × 14d + metronidazole 500 bid × 14d

190.1.0.7.6 PID (Inpatient — severe)

• Cefoxitin / cefotetan IV + doxy + metro
• Surgery if TOA + drainage

190.1.0.7.7 Neonatal

• Erythromycin 50 mg/kg/d PO × 14d (treatment)
• Topical erythromycin ointment at birth (prevention of conjunctivitis)
• Watch for pyloric stenosis (rare with erythromycin in infants)

190.1.0.7.8 Co-screening

• HIV + syphilis + gonorrhea + HBV
• Re-screen 3 mo (re-infection common)
• Partner notification + treatment

190.1.0.7.9 Doxy-PEP

• 2024 CDC: doxy 200 mg PO within 72 hr of unprotected sex — MSM, transgender women
• Reduces chlamydia ~ 70%
• Not for cisgender women (failed trial)

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