Tuberculosis

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Introduction:

Tuberculosis is an infectious disease which causes millions of death in humans. In India approximately 500,000 deaths occurs now and then. TB is an air borne disease which is caused by Mycobacterium tuberculosis. Apart from M. tuberculosis, there are many strains of Mycobacterial species like M. bovis , M .africanum , M. microti, M. caprae , M. pinnipedi i, M. canetti and M. mungi. Together these species are known to be M. tuberculosis complex. The main target of tuberculosis is the lungs (i.e. pulmonary tuberculosis) as well as other parts of the body (i.e. systemic tuberculosis). Most tuberculosis does not cause infection which is known as latent tuberculosis (i.e. they remain in inactive form). The spread of infection is due to active TB infection cough, sneeze, and fluid transmission or by aerosol in the air, and not by surface contact.

Pathogenesis of Tuberculosis:

1. The droplet nuclei containing tubercle bacilli are inhaled which enter the lungs, and travel to the alveoli.

2. These tubercle bacilli are engulfed by alveolar macrophages; the majority of these bacilli are destroyed or inhibited. The rest they multiply in the alveoli.

3. A small number of tubercle bacilli enter the bloodstream and spread throughout the body.

The tubercle bacilli may reach any part of the body including areas where TB disease is more

Likely to develop (e. g the brain, larynx, lymph node, lung, spine, bone, or kidney).

4. Within 2 to 8 weeks, special immune cells called macrophages ingest and surround the tubercle bacilli. The cells form a barrier shell, called a granuloma, that keeps the bacilli contained and under control (LTBI).

5. If the immune system cannot keep the tubercle bacilli under control, the bacilli begin...

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...uated strain of bovine tuberculosis bacillus and mycobacterium bovis that has lost its virulence.

Conclusion:

Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis. This is an air borne disease which spreads if a person is infected by tuberculosis. The infected person release droplets of tubercle bacilli which are undertaken by the other person. These droplets of bacteria travel through respiratory tract and then invade the lungs where they multiply and survive. These M. tuberculosis inhibits the phagosome-lysosome fusion and also are resistant to oxidative killing and hence survives inside the macrophages. Various drugs have been developed for the treatment of tuberculosis disease. But for the MDR-TB and XDR-TB people are left with less effective drugs. BCG vaccine is given for the prevention and also to prevent from other complications.

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