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Mycobacteria (Characteristics (Aerobic, Can withstand phagolysosomal…
Mycobacteria
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Immunology
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Host uses microbicidal molecules to kill bacteria. Acid digests mycobacteria. Generates antigens for presentation to T cells
CD4 T cells generate interferon gamma to activate intracellular killing. Genetic defects in interferon gamma or IL-12 receptors can result in mycobacterial infection
Granulomas are lesions that arise to contain mycobacteria. They prevent nutrients from entering which starves the mycobacteria. TB undergoes a dormant state inside the granuloma and can reactivate
Highly immunogenic nature of mycobacterial lipids stimulates T-cell response 3-9 weeks after infection
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Negatives: Type 4 hypersensitivity reactions, causes skin lesions, eye lesions and swelling of joints
Medically Important
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M.avium complex (MAC) - infections in AIDs, chronic lung disease
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Treatment
As mycobacteria slowly replicate, prolonged treatment is required (6 months)
Antimicrobials are given. E.g. Isoniazid for 2 months, rifampicin for 4 months
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Tuberculosis
Primary
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In apex of lungs, there is more air and less blood supply so fewer WBC to defend
Bacilli travel to lymph nodes. TB can then spread elsewhere causing TB meningitis, miliary TB, pleural TB, bone TB and genitourinary TB
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Pulmonary
Caseous material is coughed up, leaving cavity
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