Mycobacterium tuberculosis (MTB)

Definition

Mycobacterium tuberculosis ek acid-fast, aerobic bacterium hai jo tuberculosis (TB) ka main cause hai. Ye lungs ke alawa kidneys, bones, aur CNS ko bhi affect kar sakta hai.

Classification

Level →       Name

● Kingdom →Bacteria

● Phylum →   Actinobacteria

● Class →        Actinobacteria

● Order →      Corynebacteriales

● Family →     Mycobacteriaceae

● Genus →     Mycobacterium

● Species →   Mycobacterium tuberculosis

Morphology

● Gram-positive (weakly), acid-fast bacillus

● Slender, slightly curved rods

● Non-motile, non-spore forming

● Slow-growing (generation time ~15-20 hours)

Mode of Transmission

● Airborne droplets from cough, sneeze, or talking

● Close contact with infected person

● Rarely ingestion of unpasteurized milk (M. bovis)

Pathogenesis

● Bacilli inhaled → alveoli me reach

● Macrophages engulf bacilli but bacteria survive → latent infection

● Formation of granulomas (tubercles) with caseous necrosis

● Active TB develops when immunity decreases → tissue destruction and spread

● Can cause pulmonary or extrapulmonary TB

Risk Factors

● Immunocompromised (HIV, diabetes, steroid therapy)

● Malnutrition

● Age <5 or >65 years

● Close contact with TB patient

● Chronic diseases (renal failure, cancer)

● Smoking and alcohol use

Diseases Caused

● Pulmonary TB (most common)

● Extrapulmonary TB:

→Lymph nodes

→Bones (Pott’s disease)

→CNS (TB meningitis)

→Kidneys and GI tract

Diagnosis

● Specimens: Sputum, pus, urine, CSF

● Microscopy: Acid-fast bacilli (Ziehl-Neelsen stain)

● Culture: Lowenstein-Jensen medium (slow growth, 3-8 weeks)

● Molecular tests: PCR, GeneXpert

● Chest X-ray: Infiltrates, cavitation

Treatment

● First-line drugs: Isoniazid (INH), Rifampicin, Pyrazinamide, Ethambutol (2 months intensive)

● Continuation phase: INH + Rifampicin (4-7 months)

● Monitor for: Drug-resistant TB (MDR-TB, XDR-TB)

● Supportive care: Nutrition, oxygen if needed

Prevention

● BCG vaccination – mainly prevents severe TB in children.

● Mask use – by patients and healthcare workers.

● Cover mouth/nose – while coughing or sneezing.

● Good ventilation – ensure airflow in rooms and hospitals.

● Avoid close contact – stay away from active TB patients.

● Early detection & treatment – complete full course of anti-TB drugs.