Chapter 28: Infections – Mycobacteria

🫁 Mycobacterium tuberculosis · Environmental mycobacteria (NTM) · Pediatric TB · Diagnosis · Treatment · Prevention
Forfar & Arneil's Textbook of Pediatrics – Comprehensive coverage of tuberculosis in children, latent TB, drug-resistant TB, BCG, and non-tuberculous mycobacterial lymphadenitis, pulmonary disease, and management.

📖 Pediatric Mycobacterial Infections: TB & NTM

🦠 Mycobacterium tuberculosis
Airborne transmission. Primary pulmonary TB: Ghon focus + hilar lymphadenopathy (Ghon complex). Symptoms: chronic cough, fever, night sweats, weight loss, failure to thrive. Extrapulmonary: lymphadenitis, meningitis, miliary, bone/joint. Diagnosis: TST/IGRA, CXR, gastric aspirate/sputum GeneXpert, culture.
💊 TB treatment (RIPE)
Intensive phase (2 months): isoniazid (H), rifampin (R), pyrazinamide (Z), ethambutol (E). Continuation phase (4 months): HR. Directly observed therapy (DOT). Drug-resistant TB: second-line agents.
🛡️ Prevention & BCG
BCG vaccine (high-burden countries) reduces miliary TB/TB meningitis. LTBI treatment (INH 9 months or rifampin 4 months) for high-risk children. Contact tracing essential.
🌱 Environmental (NTM) Mycobacteria
M. avium complex (MAC), M. kansasii, M. abscessus, M. chelonae, M. marinum (swimming pool granuloma). Cervicofacial lymphadenitis most common in children (subacute, unilateral, non-tender). Treatment: surgical excision (preferred) or macrolide-based regimens (clarithromycin/azithromycin + rifampin/ethambutol).
⚠️ Key differences: NTM lymphadenitis: usually no systemic symptoms, normal CXR, negative TST/IGRA (or weakly positive). TB: constitutional symptoms, transmission history, CXR abnormalities.

🩺 Symptom-based approach: suspected tuberculosis

1
Identify exposure risk – Household contact with smear-positive adult TB? Recent travel from high-burden country? Homelessness, crowding, immunocompromised status (HIV).
2
Chronic symptoms (>2 weeks) – Cough, fever, night sweats, weight loss (failure to thrive), fatigue, reduced activity. Extrapulmonary: non-painful cervical lymphadenopathy, meningeal signs, Pott disease (back pain).
3
Initial evaluation – TST/IGRA (interferon-gamma release assay), chest radiograph (hilar lymphadenopathy, infiltrate, miliary pattern, effusion). Gastric aspirate/induced sputum for GeneXpert and culture.
4
Differentiation from NTM – NTM lymphadenitis: child typically well, no constitutional symptoms, CXR normal, TST often low positive (induration <10 mm). Confirm by excision biopsy and culture.

⚕️ Stepwise management of mycobacterial infections

1
Latent TB infection (LTBI) – Positive TST/IGRA with normal CXR and no symptoms. Treat with isoniazid (INH) daily for 9 months (or rifampin 4 months). Alternative: 3 months of weekly INH + rifapentine for children ≥2 years (directly observed).
2
Active pulmonary TB (drug-susceptible) – Intensive phase (2 months): RIPE (rifampin, INH, pyrazinamide, ethambutol). Continuation (4 months): rifampin + INH. Directly observed therapy (DOT) recommended. Corticosteroids for TB meningitis or pericarditis.
3
Drug-resistant TB – Refer to specialist. MDR-TB (resistance to INH+RIF) requires second-line drugs (fluoroquinolones, injectables, bedaquiline/delamanid for children). Individualized regimen.
4
NTM lymphadenitis – Surgical excision (complete) is curative. If excision not feasible or recurrence: clarithromycin or azithromycin + rifampin/ethambutol for 4-6 months. Avoid INH (resistant).
5
Disseminated NTM / pulmonary NTM – Immunocompromised (HIV, SCID) require macrolide-based combination, often with rifabutin, ethambutol, and amikacin depending on species.
📌 Public health: All cases of TB must be notified to public health authorities. Contact screening and preventive therapy for eligible contacts (especially children under 5 years).

🧠 Reflex prompts – High-yield clinical pearls

🫁 Child with persistent cough, weight loss, +ve contact with smear-positive TB. First test?
Chest X-ray and TST/IGRA. Start treatment after appropriate specimens (gastric aspirate).
🧪 What is the most sensitive initial test for TB in a young child unable to produce sputum?
Gastric aspirate or induced sputum for GeneXpert MTB/RIF (and culture).
🦠 3-year-old with unilateral, non-tender, matted cervical lymph node, afebrile, CXR normal. Likely cause?
Non-tuberculous mycobacteria (NTM), most often MAC. Excisional biopsy both diagnostic and therapeutic.
💊 First-line treatment for drug-susceptible TB in children (weight-based).
RIPE (rifampin, INH, pyrazinamide, ethambutol) for 2 months, then HR for 4 months.
⚠️ Child with HIV and possible TB. What additional test?
GeneXpert, urine LAM (lipoarabinomannan) in some settings. Always screen for TB in HIV.
🩺 TB meningitis: what adjunctive therapy improves outcome?
Dexamethasone or prednisolone (corticosteroids) reduces mortality and neurologic sequelae.
🧬 BCG vaccine complications?
BCG lymphadenitis, osteomyelitis, disseminated BCG (in immunocompromised). Avoid BCG in HIV-infected infants.
🔬 Which IGRA is commonly used for TB diagnosis?
QuantiFERON-TB Gold Plus or T-SPOT.TB (greater specificity than TST in BCG-vaccinated).
🦠 NTM that causes swimming pool granuloma (skin nodules) after trauma?
Mycobacterium marinum – treated with clarithromycin or doxycycline.
⚕️ What is the recommended duration of treatment for LTBI in a 2-year-old with recent conversion?
9 months of daily isoniazid (or 4 months rifampin).