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Habitat and Morphology of Mycobacterium tuberculosis
- Human is only the know reservoir.
- Usually found in the lungs but can also live in any part of the body.
- They may be obligate pathogen, facultative or opportunistic pathogens or free living.
- Usually infect the mono-nuclear phagocytes.
- Can also be infected by the consumption of unpasteurized milk.
- Can survive for weeks in dust, on carpets or clothes, for months in sputum.
- They are also found in soil and water.
- Straight or slightly curved thin rod shaped bacilli
- Non-sporing, non-motile, non-capsulated bacteria.
- Acid fast bacilli, neither gram +ve nor gram –ve.
- During acid fast stain, they appear bright red to intensive purple with green/blue background.
- They measure 0.5 µm x 3 µm.
- Appears in single, in pairs or small chumps.
- High content of mycolic acid (50 to 60 %).
- Cell wall is rich in lipids and waxes.
- They are wrapped together due to presence of fatty acids.
- Capable of intracellular growth.
- They are resistance to disinfectants, detergents, common antibiotics, dyes, stains, osmotic lysis, lethal oxidation, etc.