Lec5_Tuberculosis

Lec5_Tuberculosis - Tuberculosis Tuberculosis Tuberculosis...

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Tuberculosis
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Tuberculosis Tuberculosis is a complex communicable disease of humans caused by the tubercle bacilli, a group of genetically related mycobacteria also known as the Mycobacterium tuberculosis complex. The tubercle bacilli are a group of slow- growing mycobacteria that includes: M. tuberculosis M. africanum M. canettii M. bovis M. microti
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Tuberculosis Mycobacterium tuberculosis is: An obligate aerobe growing most successfully in tissues with a high oxygen content, such as the lungs. A facultative intracellular pathogen that usually infects mononuclear phagocytes (such as macrophages) Slow growing with a generation time of approximately 24 hours (as compared to 20-30 minutes for Escherichia coli ). Hydrophobic with a high lipid content in the cell wall. Because the cells are hydrophobic and tend to clump together, they are impermeable to the usual stains (Gram’s stain). Known as "acid-fast bacilli" because of their lipid-rich cell walls, which are relatively impermeable to various basic dyes unless the dyes are combined with phenol.
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Tuberculosis Source: CDC PHIL
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Tuberculosis Pathogenesis The tubercle bacilli are only moderately infectious. In a classic infection, M. tuberculosis enters the body via minute droplet nuclei deposited in the air when a person with active tuberculosis coughs, talks or sneezes.
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Tuberculosis Pathogenesis
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Tuberculosis Pathogenesis The droplet nuclei travel through the airways and are deposited on the alveolar surface, where the microbe is ingested by alveolar macrophages and begins replication. Activated macrophages release cytokines which in turn recruit more macrophages and activated T cells in an effort to control the infection.
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Tuberculosis Pathogenesis At this point, either: The inflammation-infection cycle continues and active primary tuberculosis develops The immune system contains the primary infection
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Tuberculosis Pathogenesis
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Tuberculosis Pathogenesis If the immune system CANNOT keep tubercle bacilli under control, bacilli begin to multiply rapidly and cause TB disease This process can occur in different places in the body
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Tuberculosis Pathogenesis Infection with HIV Chest x-ray findings suggestive of previous TB Substance abuse Recent TB infection Prolonged therapy with corticosteroids and other immunosuppressive therapy, such as prednisone and tumor necrosis factor-alpha [TNF-α] antagonists Organ transplant Silicosis Diabetes mellitus Severe kidney disease Certain types of cancer Certain intestinal conditions Low body weight Conditions that increase probability of LTBI progressing to TB disease
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Tuberculosis Disease TB usually affects the lungs, but it can also affect other parts of the body, such as the brain, the kidneys, or the spine.
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