Tuberculosis – TB

1. Introduction

  • Definition: Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis, primarily affecting the lungs (pulmonary TB) but can also involve other organs (extrapulmonary TB).
  • Epidemiology: TB remains a significant global health issue, with 10.6 million new cases and 1.6 million deaths reported in 2021, particularly in low- and middle-income countries.
  • Significance: TB is a leading cause of death from a single infectious agent, exacerbated by HIV co-infection and the emergence of drug-resistant strains.

2. Causes and Risk Factors

  • Causes:
    • Mycobacterium tuberculosis infection spread via airborne droplets when an infected person coughs, sneezes, or talks.
  • Risk Factors:
    • HIV/AIDS and other immunosuppressive conditions.
    • Malnutrition or poor living conditions (e.g., overcrowding).
    • Smoking and alcohol abuse.
    • Close contact with an infected person.
    • Chronic conditions like diabetes or kidney disease.

3. Pathophysiology

  • After inhalation of M. tuberculosis, the bacteria reach the alveoli and are phagocytosed by macrophages. In susceptible individuals, the bacteria multiply and spread, forming granulomas. If the immune system fails to contain the infection, it progresses to active TB, leading to tissue destruction and systemic symptoms.

4. Symptoms and Features

  • Pulmonary TB:
    • Persistent cough lasting >2 weeks, sometimes with blood-streaked sputum.
    • Chest pain, shortness of breath.
    • Unexplained weight loss, fatigue, fever, and night sweats.
  • Extrapulmonary TB:
    • TB lymphadenitis: Enlarged lymph nodes, often in the neck.
    • TB meningitis: Headache, altered mental status, and neurological deficits.
    • TB spine (Pott’s disease): Back pain and spinal deformity.
  • Latent TB: Asymptomatic, with dormant bacteria contained by the immune system.

5. Complications

  • Lung damage leading to chronic respiratory issues (fibrosis or bronchiectasis).
  • TB meningitis causing neurological sequelae.
  • Spinal deformities or paralysis in spinal TB.
  • Disseminated (miliary) TB: Multi-organ involvement, which can be fatal.

6. Diagnosis

  • Clinical Features: Symptoms like persistent cough, fever, and weight loss warrant further investigation.
  • Diagnostic Tests:
    • Microscopy and Culture: Acid-fast bacilli (AFB) smear and mycobacterial culture from sputum or tissue samples.
    • Molecular Tests: Xpert MTB/RIF for rapid detection of TB and rifampicin resistance.
    • Imaging: Chest X-ray or CT scan for pulmonary involvement.
    • Latent TB Testing: Tuberculin skin test (TST) or interferon-gamma release assay (IGRA).

7. Management Overview

  • Goals: Eradicate infection, prevent transmission, and reduce complications or drug resistance.
  • Approach: Combination of multidrug therapy for 6–12 months (active TB) and shorter regimens for latent TB.

8. Treatment Options with Cost (USD)

  • First-line Anti-TB Drugs:
    • Isoniazid (INH): ~$20–$50 per month.
    • Rifampicin (RIF): ~$30–$60 per month.
    • Pyrazinamide (PZA): ~$10–$30 per month.
    • Ethambutol (EMB): ~$10–$30 per month.
  • Latent TB Treatment:
    • INH: ~$20–$50 per month for 6–9 months.
    • Rifapentine + INH: ~$50–$100 for a 12-week course.

9. Advanced Treatment Options with Cost (USD)

  • Drug-Resistant TB (MDR-TB/XDR-TB):
    • Bedaquiline: ~$1,000–$3,000 per course.
    • Linezolid: ~$800–$1,500 per course.
    • Delamanid: ~$1,500–$2,000 per course.
  • Hospitalisation: For severe TB or complications: ~$10,000–$30,000.

10. Pharmacological Treatment

  • First-line Regimen (Active TB):
    • Intensive phase: Isoniazid, rifampicin, pyrazinamide, and ethambutol for 2 months.
    • Continuation phase: Isoniazid and rifampicin for 4 months.
  • Latent TB: Isoniazid for 6–9 months or rifapentine + INH for 12 weeks.
  • Drug-Resistant TB: Individualised regimens based on susceptibility testing.

11. Medication Tables

Table 1: Doses and Side Effects

DrugIndicationDoseCommon Side Effects
IsoniazidFirst-line TB treatment5 mg/kg daily (max 300 mg)Hepatitis, peripheral neuropathy
RifampicinFirst-line TB treatment10 mg/kg daily (max 600 mg)Orange urine, liver toxicity
PyrazinamideIntensive phase of TB20–25 mg/kg dailyGI upset, joint pain, hepatitis
EthambutolFirst-line TB treatment15–20 mg/kg dailyOptic neuritis (monitor vision)
BedaquilineMDR-TB treatment400 mg daily for 2 weeks, then 200 mg 3 times/weekQT prolongation, nausea

Table 2: Brand Names and Approximate Costs (USD)

DrugBrand NamesApprox. Cost
IsoniazidLaniazid, Nydrazid$20–$50 per month
RifampicinRifadin, Rimactane$30–$60 per month
PyrazinamideRifater (combination drug)$10–$30 per month
EthambutolMyambutol$10–$30 per month
BedaquilineSirturo$1,000–$3,000 per course

12. Lifestyle Interventions

  • Adequate nutrition to boost immunity and promote recovery.
  • Avoid smoking, alcohol, and other immunosuppressive activities.
  • Practice good hygiene, such as covering the mouth when coughing, to reduce transmission.
  • Maintain adherence to the full course of treatment to prevent drug resistance.

13. Monitoring Parameters

  • Regular sputum tests (smear and culture) to monitor response to treatment.
  • Liver function tests during therapy, especially for INH, RIF, or PZA.
  • Visual acuity and colour vision assessment during ethambutol use.
  • Electrocardiogram (ECG) monitoring for patients on bedaquiline or other QT-prolonging agents.

14. Patient Counseling Points

  • Emphasise the importance of completing the full course of TB treatment, even if symptoms improve.
  • Educate on possible side effects of medications and the need for regular follow-ups.
  • Encourage respiratory hygiene to prevent spreading the infection to others.
  • Explain that latent TB treatment reduces the risk of developing active disease.

15. Special Populations

  • In Children: Use weight-based dosing; avoid ethambutol in children under 5 unless essential.
  • In Pregnancy: Use standard first-line drugs (avoid streptomycin due to ototoxicity); prioritise latent TB treatment after delivery unless high risk.
  • In HIV Patients: Monitor drug interactions between rifampicin and antiretroviral therapy (ART).

16. Prevention

  • BCG Vaccination: Administered to infants in high-burden areas to prevent severe TB forms like meningitis.
  • Infection Control: Early diagnosis, treatment of active cases, and proper ventilation in healthcare settings.
  • Chemoprophylaxis: Isoniazid for close contacts with latent TB, particularly in high-risk groups.

17. FAQs

  1. What causes tuberculosis (TB)?
    Answer: A bacterial infection caused by Mycobacterium tuberculosis.
  2. How is TB transmitted?
    Answer: Through airborne droplets from an infected person.
  3. What are the symptoms of TB?
    Answer: Persistent cough, fever, night sweats, weight loss, and fatigue.
  4. How is TB diagnosed?
    Answer: Through sputum microscopy, molecular tests, and imaging like chest X-rays.
  5. Is TB curable?
    Answer: Yes, with a full course of appropriate antibiotics.
  6. What is latent TB?
    Answer: A dormant infection without symptoms, which can reactivate if untreated.
  7. How long does TB treatment last?
    Answer: Typically 6–9 months for drug-sensitive TB.
  8. What are drug-resistant TB and MDR-TB?
    Answer: Forms of TB resistant to first-line drugs like isoniazid and rifampicin.
  9. What is the role of the BCG vaccine?
    Answer: It prevents severe TB forms in children, like meningitis.
  10. Can TB return after treatment?
    Answer: Yes, if treatment is incomplete or immunity is weakened.
  11. What foods help with TB recovery?
    Answer: Protein-rich and vitamin-rich diets, including fruits, vegetables, and lean meats.
  12. Can TB spread through physical contact?
    Answer: No, it spreads via respiratory droplets, not physical touch.
  13. Are TB drugs safe during pregnancy?
    Answer: Most first-line drugs are safe; consult a healthcare provider.
  14. How can TB be prevented in close contacts?
    Answer: Through chemoprophylaxis and regular health monitoring.
  15. Is TB common in developed countries?
    Answer: Less common but still present, especially in immigrants and immunocompromised individuals.