Overview

Tuberculosis (TB) is a contagious bacterial infection primarily affecting the lungs but can impact other organs. It is caused by Mycobacterium tuberculosis. TB remains a major global health concern due to its prevalence, drug resistance, and social implications.

Pathophysiology

  • Causative Agent: Mycobacterium tuberculosis (MTB), a slow-growing, acid-fast bacillus.
  • Transmission: Airborne droplets from coughing, sneezing, or speaking.
  • Infection Process:
    • MTB enters alveoli, is engulfed by macrophages.
    • Bacteria can survive and multiply within macrophages.
    • Formation of granulomas (tubercles) as immune response.
    • Latent TB: Bacteria remain dormant; no symptoms.
    • Active TB: Bacteria multiply, leading to symptoms and spread.

TB Infection Process

Clinical Features

  • Pulmonary TB: Persistent cough, hemoptysis, chest pain, night sweats, weight loss, fever.
  • Extrapulmonary TB: Can affect lymph nodes, bones, kidneys, central nervous system.
  • Latent TB: No symptoms, not contagious, can reactivate.

Diagnosis

  • Mantoux Tuberculin Skin Test (TST)
  • Interferon-Gamma Release Assays (IGRAs)
  • Chest X-ray
  • Sputum Smear Microscopy
  • Culture and PCR for MTB DNA

Treatment

  • First-line Drugs: Isoniazid, Rifampicin, Ethambutol, Pyrazinamide (6-month regimen).
  • Drug-resistant TB: Requires second-line drugs, longer and more toxic regimens.
  • Directly Observed Therapy (DOT): Ensures compliance, reduces resistance.

Surprising Facts

  1. TB is the leading cause of death from a single infectious agent, surpassing HIV/AIDS (WHO, 2022).
  2. Over 25% of the world’s population is estimated to have latent TB infection.
  3. TB can remain dormant for decades and reactivate when the immune system weakens.

Global Impact

  • Prevalence: In 2022, 10.6 million people fell ill with TB worldwide; 1.6 million died (WHO).
  • High-Burden Countries: India, Indonesia, China, Philippines, Pakistan, Nigeria, Bangladesh, South Africa.
  • Drug Resistance: Multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) are rising threats.
  • Socioeconomic Factors: Poverty, malnutrition, HIV infection, and overcrowding increase risk.
  • COVID-19 Impact: The pandemic disrupted TB services, leading to increased deaths and missed diagnoses (Lancet, 2021).

TB – A Story

Fatima, a 32-year-old mother in rural India, started coughing persistently. She dismissed it as a seasonal cold, but weeks later, she developed night sweats and lost weight. Her village clinic diagnosed her with pulmonary TB. Fatima’s treatment required daily visits for DOT, straining her family’s finances and time. Her neighbors avoided her, fearing infection. Despite the challenges, Fatima completed her treatment and recovered, but the stigma lingered. Her story highlights the intersection of biology, social impact, and the importance of accessible healthcare.

Ethical Issues

  • Stigma and Discrimination: TB patients often face social isolation, impacting mental health and willingness to seek care.
  • Mandatory Isolation: Balances public health safety with individual rights; can lead to human rights concerns.
  • Access to Care: Disparities in diagnosis and treatment for marginalized groups.
  • Drug Development: High costs and limited incentives for pharmaceutical companies to develop new TB drugs.
  • Global Health Equity: Ensuring all countries have access to effective diagnostics and treatments.

Recent Research

  • 2023 Study: A Nature Medicine article (“Development of a new vaccine candidate for tuberculosis,” Nature Medicine, 2023) reported promising results for a novel TB vaccine (M72/AS01E), showing 50% efficacy in preventing active TB in people with latent infection.
  • Drug Resistance: A 2022 Lancet study highlighted the growing prevalence of MDR-TB and the urgent need for new antibiotics and treatment strategies.

Prevention

  • BCG Vaccine: Offers partial protection, especially in children.
  • Infection Control: Ventilation, masks, rapid diagnosis, and treatment.
  • Contact Tracing: Identifying and treating latent infections to prevent spread.

Summary Table

Aspect Details
Cause Mycobacterium tuberculosis
Transmission Airborne droplets
Symptoms Cough, fever, night sweats, weight loss
Diagnosis TST, IGRA, chest X-ray, sputum test
Treatment Isoniazid, Rifampicin, Ethambutol, Pyrazinamide
Prevention BCG vaccine, infection control
Global Impact 10.6 million cases/year, 1.6 million deaths (2022)
Ethical Issues Stigma, access, isolation, drug development

Revision Checklist

  • [x] Understand TB pathophysiology
  • [x] Recognize symptoms and diagnosis methods
  • [x] Know treatment regimens and drug resistance
  • [x] Appreciate global impact and ethical issues
  • [x] Recall surprising facts and recent research

References

  • World Health Organization. Global Tuberculosis Report 2022.
  • Nature Medicine. “Development of a new vaccine candidate for tuberculosis,” 2023.
  • The Lancet. “Impact of COVID-19 on tuberculosis control,” 2021.

TB Global Impact