CHLAMYDIA

CHLAMYDIA

definition – Chlamydia is an obligate intracellular gram‑negative bacterium (Chlamydia trachomatis) causing several human diseases

causes – transmission by unprotected vaginal, anal or oral sex; mother‑to‑child during delivery; contaminated fomites (rare)

types / biovars –

1. trachoma biovar → ocular trachoma, inclusion conjunctivitis, adult inclusion conjunctivitis
2. lymphogranuloma venereum (LGV) biovar → genital ulcer, inguinal buboes, proctocolitis
3. urogenital biovar (serovars D‑K) → urethritis, cervicitis, pelvic inflammatory disease, epididymitis, prostatitis, neonatal conjunctivitis & pneumonia

morphology – two forms:
• elementary body (EB) – small, dense, extracellular, infectious
• reticulate body (RB) – larger, metabolically active, replicative, intracellular

life cycle (step‑wise) –

1. EB attaches to mucosal epithelial cell →
2. EB internalised by endocytosis →
3. EB‑containing vacuole avoids lysosomal fusion →
4. EB → RB conversion inside inclusion →
5. RB multiplies by binary fission →
6. RB → EB re‑differentiation →
7. Inclusion ruptures → release of EB to infect new cells

memory trick – “Eager Bunnies Run, Clone, Escape, Repeat” (E‑B attach, B‑enter, R‑replicate, C‑convert, E‑exit, R‑repeat)

pathogenesis (step‑wise) –

1. EB binds to heparan‑sulfate receptors on epithelial surface →
2. Endocytosis forms an inclusion body →
3. Inclusion prevents phagolysosome fusion →
4. EB transforms to RB and uses host ATP for replication →
5. RBs fill inclusion, produce large numbers of EB →
6. Host cell cytoskeleton disrupted, cell swells →
7. Cell lysis releases EB → spread to adjacent cells

clinical features –
• ocular trachoma: chronic follicular conjunctivitis, pannus, corneal scarring → blindness (Robbins)
• LGV: painless genital ulcer → tender inguinal lymphadenopathy (buboes) → proctocolitis in MSM
• urogenital infection (women): mucopurulent cervical discharge, dysuria, lower abdominal pain, infertility risk
• urogenital infection (men): urethral discharge, dysuria, epididymitis, prostatitis
• neonates: conjunctivitis (day 2‑5) → “pink eye”, pneumonia (day 5‑14)

complications –
• pelvic inflammatory disease → tubo‑ovarian abscess, ectopic pregnancy, infertility (Harsh Mohan)
• chronic scarring in trachoma → entropion, trichiasis, corneal opacity (Ananthanarayan)
• LGV → strictures, fistulae, chronic lymphatic obstruction (Chatterjee)
• neonatal pneumonia → respiratory distress, bronchopneumonia (Robbins)

diagnosis –

1. nucleic acid amplification test (NAAT) from urine, endocervical or urethral swab – most sensitive (NCH)
2. direct fluorescent antibody (DFA) for EB in ocular smears (optional)
3. culture in cycloheximide‑treated McCoy cells – rarely done (research)
4. serology (IgM/IgG) useful for LGV staging, not for acute urogenital infection

management –
• first‑line single‑dose azithromycin 1 g orally OR doxycycline 100 mg twice daily for 7 days (MUHS guideline)
• pregnant women: azithromycin or amoxicillin (if azithro contraindicated)
• treat sexual partners simultaneously → prevent reinfection
• advise abstinence for 7 days after single dose or until completion of doxycycline course
• follow‑up NAAT at 3 weeks to confirm cure (especially in pregnant women)

prevention –
• consistent condom use → reduces transmission
• routine screening of sexually active persons ≤30 years or high‑risk groups
• health education on safe sex practices (BHMS curriculum)
• prompt treatment of infected pregnant women to prevent neonatal disease

key exam points –
• C. trachomatis is obligate intracellular → only EB can survive outside cell, RB replicates inside
• trachoma → endemic in poor hygiene areas, repeated infections → scarring blindness
• LGV → serovars L1‑L3, primary lesion often unnoticed, secondary stage with tender buboes
• urogenital serovars D‑K → most common bacterial STI, often silent in women → PID risk
• neonatal conjunctivitis → prophylactic erythromycin eye ointment at birth (NCH)
• NAAT is gold standard – >95 % sensitivity, >99 % specificity.