Pathogenesis of Tuberculosis
Inhalation: Contaminated Dusts or Droplets
- This is the most common route of transmission of tuberculosis from person to
person. Uniquely high resistance of M. tuberculosis to drying is responsible for this. M.
tuberculosis within sputa can survive very long even after they are dried and air-borne.
This is why tuberculosis is often acquired in over-crowded housing, jail cells, and other
climatic conditions that exacerbated exposure. Physicians and other health care personnel
are constantly at risk of infection.
- Most infections can be prevented or at least minimized by proper use of mask,
sanitary care of rooms, and installation of good ventilation system.
Ingestion: Contaminated Milk (Uncommon in the Western World) - Tuberculosis Due
to M. Bovis.
- Milk is routinely pasteurized to kill pathogens (that include tubercle bacilli).
Spread, Multiplication and Damage
Tubercle bacilli do not produce exotoxins or endotoxin. The severe manifestations of
tuberculosis are linked to host reactions to the organisms; damage is caused by
uncontrolled, progressive, chronic inflammation, and by organisms living with macrophages.
It follows that infection has different manifestations in a "virgin" host than
in a person who has been infected previously. Tuberculosis manifests itself in two major