Overview

Tuberculosis (TB) is a contagious bacterial infection primarily affecting the lungs but can involve other organs. It is caused by Mycobacterium tuberculosis. Despite being preventable and curable, TB remains a leading cause of infectious disease-related deaths globally.

Etiology and Pathogenesis

  • Causative Agent: Mycobacterium tuberculosis, an aerobic, acid-fast bacillus.
  • Transmission: Airborne droplets from coughing, sneezing, or speaking by an infected person.
  • Pathogenesis:
    • Inhaled bacilli reach alveoli.
    • Macrophages engulf bacteria but may not destroy them.
    • Bacteria can remain dormant (latent TB) or multiply, leading to active disease.
    • Formation of granulomas (tubercles) as immune response.

Clinical Manifestations

Pulmonary TB

  • Persistent cough (>2 weeks)
  • Hemoptysis (coughing blood)
  • Chest pain
  • Weight loss
  • Night sweats
  • Fever and chills

Extrapulmonary TB

  • Lymph nodes, bones, kidneys, CNS, and other organs may be affected.
  • Symptoms vary by organ system involved.

Diagnosis

  • Tuberculin Skin Test (TST): Detects immune response to TB proteins.
  • Interferon-Gamma Release Assays (IGRA): Blood test for TB infection.
  • Chest X-ray: Identifies lung abnormalities.
  • Sputum Smear Microscopy: Detects acid-fast bacilli.
  • Nucleic Acid Amplification Tests (NAAT): Rapid detection of TB DNA.
  • Culture: Gold standard, but slow (weeks for results).

Diagram: TB Infection Process

TB Infection Process

Treatment

  • First-line Drugs: Isoniazid, Rifampicin, Ethambutol, Pyrazinamide.
  • Duration: 6 months (2 months intensive, 4 months continuation).
  • Drug-Resistant TB: Requires longer, more complex regimens.
  • Directly Observed Therapy (DOT): Ensures adherence.

Prevention

  • BCG Vaccine: Provides partial protection, especially in children.
  • Infection Control: Ventilation, masks, and rapid diagnosis in healthcare settings.
  • Contact Tracing: Identifies and tests exposed individuals.

Emerging Technologies

  • Whole Genome Sequencing: Rapid detection of drug resistance mutations (WHO, 2023).
  • CRISPR-based Diagnostics: Ultra-sensitive detection of TB DNA in sputum.
  • Digital Adherence Technologies: Smartphone apps and smart pillboxes to improve medication adherence.
  • AI-powered Imaging: Automated chest X-ray analysis for faster screening.
  • Novel Vaccines: Multiple candidates in clinical trials aim to improve efficacy over BCG.

Impact on Daily Life

  • Work and School: TB can cause prolonged absenteeism due to illness or isolation.
  • Stigma: Social discrimination may lead to psychological distress and delay in seeking care.
  • Economic Burden: Costs of treatment, lost income, and long-term health effects.
  • Public Health: TB outbreaks can strain healthcare systems, especially in low-resource settings.

Surprising Facts

  1. TB is Ancient: Evidence of TB has been found in Egyptian mummies dating back over 4,000 years.
  2. Latent TB Reservoir: About one-quarter of the world’s population is estimated to have latent TB infection, with no symptoms.
  3. Drug Resistance: Multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) are increasing threats, complicating global eradication efforts.

Recent Research

A 2022 study published in The Lancet Global Health demonstrated that a new, shorter 4-month treatment regimen for drug-sensitive TB is as effective as the traditional 6-month course, potentially improving patient adherence and outcomes (Lancet Global Health, 2022).

Glossary

  • Acid-fast Bacilli: Bacteria that resist decolorization by acids during staining, characteristic of Mycobacterium tuberculosis.
  • BCG Vaccine: Bacillus Calmette–Guérin vaccine, used to prevent TB.
  • Granuloma: A mass of immune cells formed to contain TB bacteria.
  • Latent TB: Infection with TB bacteria without active disease or symptoms.
  • MDR-TB: Multidrug-resistant tuberculosis, resistant to at least isoniazid and rifampicin.
  • NAAT: Nucleic Acid Amplification Test, a rapid molecular diagnostic tool.
  • DOT: Directly Observed Therapy, where health workers supervise TB medication intake.

References

Additional Diagram: TB Granuloma Formation

TB Granuloma

Summary Table: TB Key Points

Aspect Details
Causative Agent Mycobacterium tuberculosis
Transmission Airborne droplets
Diagnosis TST, IGRA, X-ray, Sputum, NAAT, Culture
Treatment 6-month drug regimen; longer for drug-resistant TB
Prevention BCG vaccine, infection control, contact tracing
Emerging Technologies Genomics, CRISPR, AI, digital adherence, new vaccines
Impact Health, social, economic, psychological

Note: The human brain has more connections than there are stars in the Milky Way, highlighting the complexity of both human biology and infectious diseases like TB.