Mycobacterium tuberculosis

Classification

Kingdom: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Order: Actinomycetales
Family: Mycobacteriaceae
Genus: Mycobacterium
Species: Mycobacterium tuberculosis

Morphology

Shape: Rod-shaped (bacillus)
Size: ~2.0–4.0 μm in length, ~0.3–0.6 μm in diameter
Gram Stain: Gram-positive (acid-fast due to mycolic acid in cell wall)
Arrangement: Single, pair, or in clusters
Motility: Non-motile
Special Features: Acid-fast due to thick waxy cell wall containing mycolic acid, resistant to many antibiotics

Habitat & Distribution

Natural Habitat: Human lungs and other tissues
Geographic Distribution: Worldwide, particularly in areas with poor healthcare
Human Association: Pathogenic
Transmission: Aerosol droplets (coughing, sneezing)

Mycobacterium tuberculosis is a major bacterial pathogen that causes tuberculosis, primarily affecting the lungs but can also spread to other parts of the body, leading to severe disease.

Virulence Factors: Mycolic acid in the cell wall, Cord factor, ESAT-6 protein, ability to survive in macrophages
Associated Diseases: Tuberculosis (Pulmonary and extrapulmonary forms)
Clinical Symptoms: Cough, chest pain, weight loss, night sweats, fever, hemoptysis (coughing up blood)
High-Risk Groups: Immunocompromised individuals, people with HIV/AIDS, close contacts of infected individuals, people living in crowded or poorly ventilated areas

The ability of Mycobacterium tuberculosis to evade the immune system and its ability to cause chronic, latent infection make it a significant global health threat, requiring aggressive treatment strategies.

The diagnosis of Mycobacterium tuberculosis infection relies on several clinical and laboratory tests.

Diagnostic Methods

Chest X-ray: Detects pulmonary tuberculosis and its complications
Sputum Smear Microscopy: Detects acid-fast bacilli (AFB) in sputum samples
PCR: Identifies M. tuberculosis DNA
Tuberculin Skin Test (TST): Assesses previous exposure to M. tuberculosis (used for screening)
Culture of Mycobacteria: Gold standard for diagnosing tuberculosis (slow-growing, may take weeks)

Treatment Approaches

First-line Treatments: Rifampin, isoniazid, pyrazinamide, and ethambutol (combined in a regimen known as DOTS - Directly Observed Treatment, Short-course)
Drug-Resistant Tuberculosis: Multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) require longer treatment with second-line drugs
Antimicrobial Resistance: Rising cases of drug-resistant strains, particularly MDR-TB and XDR-TB, pose significant treatment challenges
Supportive Care: Proper nutrition, managing symptoms, and treating comorbid conditions (such as HIV/AIDS) are essential

Prevention Strategies

Improved sanitation and hygiene practices, including handwashing and respiratory hygiene (covering coughs and sneezes)
Proper ventilation in living spaces to reduce airborne transmission
BCG vaccination to provide some protection against severe forms of tuberculosis in children
Regular screening for high-risk groups (e.g., healthcare workers, people living with HIV/AIDS)
Adherence to TB treatment regimens to prevent the spread of infection

Preventing Mycobacterium tuberculosis infections involves improving sanitation, reducing transmission in high-risk areas, and ensuring prompt diagnosis and treatment.

Global Impact

Mycobacterium tuberculosis remains a leading cause of infectious disease worldwide, especially in low- and middle-income countries where access to healthcare is limited.

~1.8B

Approximately 1.8 billion people are infected with M. tuberculosis, most of whom have the inactive form of the disease.

Despite progress in controlling tuberculosis, it remains a major global health issue, particularly in regions with poor sanitation, overcrowded living conditions, and high rates of HIV co-infection.