CHLAMYDIA TRACHOMATIS (LGV) – COMPLETE MICROBIOLOGY

🌟 LGV = Lymphogranuloma venereum

🌟 Caused by C. trachomatis serovars L1, L2, L3

🌟 Leads to painless small ulcer + massive painful lymph nodes (“buboes”)

⭐ 20% HIGH-YIELD THAT GIVES 80% MARKS

1. Organism: Obligate intracellular Gram-negative bacterium
2. Serovars causing LGV: L1, L2, L3
3. Special feature: Has two forms → elementary body (infectious) & reticulate body (replicating)
4. Cannot make ATP → “energy parasite” → must live inside cells
5. Disease pattern:
• Stage 1: Small painless ulcer (often unnoticed)
• Stage 2: Painful massive inguinal buboes
• Stage 3: Chronic fibrosis, strictures, elephantiasis
6. Diagnosis: NAAT/ PCR (gold standard)
7. Treatment: Doxycycline 100 mg BD × 21 days
8. Complication: Rectal strictures, proctocolitis (esp. in MSM)
9. Differentiation: Ulcer painless, nodes painful (opposite of chancroid)
10. No Gram stain seen → because it is intracellular + no peptidoglycan

If you learn only these → you score.

🔬 FULL MICROBIOLOGY – EASY EXPLANATION

1. Classification

• Family: Chlamydiaceae
• Species: Chlamydia trachomatis
• Serovars:
• A–C → trachoma
• D–K → urogenital infections + neonatal conjunctivitis
• L1–L3 → LGV (exam favourite)

📌 Memory Hint:

“L = LGV (L1, L2, L3).”

2. Structure and Special Features

Chlamydia trachomatis is unique:

A. Gram-negative but not seen on Gram stain

Reasons:

• Very thin peptidoglycan
• Intracellular location
• Poor uptake of dye

B. Cannot make ATP

→ It is an obligate intracellular parasite

→ Must invade host cells (epithelial cells, macrophages)

C. Has 2 distinct life forms

1. Elementary body (EB)

• Infectious form
• Small, extracellular
• Enters host cells → endocytosis
• Like a "spore", survives outside briefly

2. Reticulate body (RB)

• Non-infectious
• Intracellular
• Actively replicates via binary fission
• Converts back to EB before release

💡 Memory Trick:

• EB = Enters
• RB = Reproduces

3. Life Cycle (VERY EXAM FAVOURITE)

1. EB attaches to host epithelial cell
2. EB enters via endocytosis
3. EB → RB inside vacuole
4. RB multiplies
5. RB → EB conversion
6. EB released → infects more cells

Time: ~48–72 hours

4. Transmission

• Sexual contact (vaginal, anal, oral)
• LGV is especially common in MSM (men who have sex with men)
• Can occur in heterosexuals as well

5. Pathogenesis – How LGV Causes Disease

• L1–L3 strains are more invasive
• Spread to lymphatic system
• Infection leads to:
• Lymphangitis
• Lymphadenitis
• Granulomatous inflammation
• Necrosis of nodes

This explains the classic buboes.

🩺 6. Clinical Stages of LGV

Stage 1 – Primary lesion (Day 3–12)

• Small painless papule/ulcer
• Often unnoticed → heals quickly
• Few or no symptoms

Stage 2 – Secondary stage (2–6 weeks)

Most recognisable stage

• Marked painful inguinal/femoral lymphadenopathy
• “Groove sign” (between inguinal ligament and nodes)
• Fever, malaise may occur
• Nodes may suppurate → rupture → draining sinuses

Stage 3 – Late stage (months–years)

Chronic inflammation → fibrosis

• Rectal strictures
• Elephantiasis of genital organs
• Infertility
• Proctocolitis

(Especially with anal sex exposure)

🆚 HOW TO DIFFERENTIATE LGV FROM OTHER GENITAL ULCERS (Exam table)

🔬 7. Diagnosis

1. NAAT (PCR)

• The gold standard
• Detects chlamydial DNA from:
• Ulcer swab
• Lymph node aspirate
• Rectal swab

2. Serology

Helpful but not diagnostic.

3. Lymph node aspirate

• "Buboes" aspirated → PCR

4. Rule out other ulcers

• Syphilis tests (VDRL)
• HSV PCR
• H. ducreyi PCR/culture

💊 8. Treatment (VERY HIGH-YIELD)

First-line:

• Doxycycline 100 mg BD for 21 days ✔ (key exam answer)

Alternatives:

• Erythromycin 500 mg QID × 21 days
• Azithromycin weekly × 3 weeks (less used)

Management of Buboes:

• Needle aspiration (preferred)
• Avoid incision (risk of chronic fistula)

💥 9. Complications

• Chronic genital elephantiasis
• Anal strictures
• Proctocolitis
• Infertility
• Reactive arthritis (Reiter’s syndrome)

🎯 ABSOLUTE MUST-MEMORISE (20% → 80% SCORE)

1. Serovars → L1, L2, L3 cause LGV
2. Obligate intracellular bacteria; cannot make ATP
3. Two forms: EB (infectious), RB (replicating)
4. Stage 1: Painless ulcer
5. Stage 2: Painful enlarged lymph nodes (“buboes”)
6. Diagnosis → PCR
7. Treatment → doxycycline 21 days
8. Complication → strictures, elephantiasis, proctocolitis

🦠 CHLAMYDIA TRACHOMATIS (LGV) — COMPLETE MICROBIOLOGY & CLINICAL MASTER TABLE

1️⃣ ORGANISM & CLASSIFICATION

2️⃣ STRUCTURAL & UNIQUE MICROBIOLOGICAL FEATURES

3️⃣ LIFE CYCLE (VERY HIGH-YIELD)

Complete cycle duration: 48–72 hours

4️⃣ TRANSMISSION

5️⃣ PATHOGENESIS (WHY LGV IS DIFFERENT)

6️⃣ CLINICAL STAGES OF LGV

STAGE-WISE TABLE

7️⃣ CLASSIC EXAM CLINICAL SIGN

8️⃣ DIFFERENTIAL DIAGNOSIS — GENITAL ULCER TABLE

9️⃣ DIAGNOSIS

🔟 TREATMENT (EXAM-CRITICAL)

1️⃣1️⃣ COMPLICATIONS