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Tuberculosis

Unit 6 Human Disease. Tuberculosis. TB Photos. Pathophysiology – Borders – Spring 2011. Overview.

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Tuberculosis

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  1. Unit 6 Human Disease Tuberculosis TB Photos Pathophysiology – Borders – Spring 2011

  2. Overview TB disease is caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain. If not treated properly, TB can be fatal.  TB Overview Video

  3. Tuberculosis Infectious Agent • Mycobacterium tuberculosis is a rod-shaped, nonmotile,. Mode of Transmission • Tuberculosis (TB) transmission occurs when a contagious patient coughs, spreading the bacilli through the airborne route to a person sharing the same air space. • Bovine TB (caused by the closely related Mycobacterium bovis) can be transmitted by ingestion of contaminated, unpasteurized dairy products from infected cattle.

  4. Microbiology • Aerobic • Bacillus (rod-shaped) • Non-spore forming • Non-motile • Cell wall – mycolic acid – retains acid fast stain

  5. Epidemiology • Most cases in the US are due to reactivation, especially amongst immigrants • Highest risk of progression to active TB is within 2 years of seroconversion • Increase in incidence in late 1980s-early 90s largely due to HIV • Must be reported to the health department

  6. Transmission • Transmitted by airborne particles • Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted • Infection can result from only 1-5 bacteria entering a terminal alveolus • Only those with active pulmonary TB are infectious

  7. Pathogenesis • Inhalation -> phagocytosis by alveolar macrophages • Bacterial multiplication occurs intracellularly • Lymphatic spread to regional lymph nodes or hematogenous dissemination • Immune response results in granuloma formation (containment of infection) • Cell death in the granuloma results in caseous necrosis • Bacteria can remain dormant in the granuloma

  8. Symptoms/Signs • Fever • Night sweats • Cough • Hemoptysis-coughing up of blood or of blood-stained sputum • Pleurisy-inflammation of the lining of the lungs • Weight loss • Fatigue

  9. Tuberculosis • Globally there are nearly 9 million new TB cases and nearly 2 million TB-related deaths each year. • TB occurs throughout the world, but the incidence varies greatly. • In the United States, the annual incidence is less than 5 per 100,000 persons, but in some countries in sub-Saharan Africa and Asia the annual incidence is several hundred per 100,000. • Drug-resistant TB is of increasing concern. Multidrug-resistant or MDR TB is resistant to at least two of the most effective drugs.

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