Mycobacterium tuberculosis

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Mycobacterium tuberculosis

  1. 1. Mycobacterium tuberculosis Dr Kamran Afzal Asst Prof Microbiology
  2. 2. Tuberculosis - The Captain of Death
  3. 3. Historical background <ul><li>Neolithic time </li></ul><ul><ul><li>2400 BC - Egyptian mummies spinal columns </li></ul></ul><ul><li>460 BC </li></ul><ul><ul><li>Hippocrates, Greece </li></ul></ul><ul><ul><li>First clinical description: Phthisis / Consumption </li></ul></ul><ul><li>500-1500 AD </li></ul><ul><ul><li>Roman occupation of Europe, it spread to Britain </li></ul></ul><ul><li>1650-1900 AD </li></ul><ul><ul><li>‘ White plague’ of Europe </li></ul></ul><ul><ul><li>1:5 deaths </li></ul></ul>
  4. 4. <ul><li>1890 (Robert Koch) </li></ul><ul><ul><li>Discovery of staining technique that identified Bacillus tuberculosis </li></ul></ul><ul><ul><li>Definite diagnosis made possible and thus treatment could begin </li></ul></ul><ul><ul><li>Tuberculin’s diagnostic use discovered </li></ul></ul>
  5. 5. <ul><li>1908-1920 </li></ul><ul><ul><li>Vaccine (BCG) </li></ul></ul><ul><li>1943 (Selman Abraham Waksman) </li></ul><ul><ul><li>Streptomycin discovered </li></ul></ul><ul><ul><li>Injections dramatically recovered TB patients </li></ul></ul>
  6. 6. Mycobacteria <ul><li>The name mycobacterium means “fungus bacterium” due to fungus-like pellicle formed by Mycobacterium tuberculosis in liquid media </li></ul>
  7. 7. Species differentiation <ul><li>Order - Actinomycetales </li></ul><ul><li>Family - Mycobacteriaceae </li></ul><ul><li>Genus - Mycobacterium </li></ul><ul><li>Usually grouped into 2 divisions </li></ul><ul><ul><li>Typical mycobacteria (MTb Complex) </li></ul></ul><ul><ul><li>Atypical mycobacteria </li></ul></ul><ul><ul><ul><li>Slow growing > 7 days </li></ul></ul></ul><ul><ul><ul><li>Rapidly growing < 7 days </li></ul></ul></ul>
  8. 8. Mycobacterium tuberculosis Complex <ul><li>Mycobacterium tuberculosis </li></ul><ul><li>Mycobacterium bovis </li></ul><ul><li>Mycobacterium africanum </li></ul><ul><li>Mycobacterium microti </li></ul><ul><li>Mycobacterium canetii </li></ul>
  9. 9. <ul><li>M.avium-intracellulare complex </li></ul><ul><li>M. scrofulaceum </li></ul><ul><li>M. xenopi </li></ul><ul><li>M. paratuberculosis </li></ul><ul><li>M. malmoense </li></ul><ul><li>M. marinum </li></ul><ul><li>M. farcinogenes </li></ul><ul><li>M. k ansasii </li></ul><ul><li>M. haemophilum </li></ul><ul><li>M. chelonae </li></ul><ul><li>M. fortuitum </li></ul><ul><li>M. ulcerans </li></ul><ul><li>M. intermedium </li></ul><ul><li>Mycobacteria other than tuberculosis (MOTT) </li></ul><ul><li>Atypical Mycobacteria </li></ul>Nontuberculous Mycobacteria (NTM)
  10. 10. Gen Characteristics - Mycobacteria <ul><li>80 species, 20 are known pathogens </li></ul><ul><li>Gram positive but are not easily stained </li></ul><ul><li>Non-encapsulated and do not form spores </li></ul><ul><li>Acid-fast </li></ul><ul><li>Resistant to drying and chemical disinfectants but sensitive to heat and UVL </li></ul>
  11. 11. <ul><li>Lipids (60% of the cell wall weight) </li></ul><ul><ul><li>Mycolic acid – responsible for acid fastness </li></ul></ul><ul><ul><li>Phospholipids – induce caseation necrosis </li></ul></ul><ul><ul><li>Cord factor (trehaloses) </li></ul></ul><ul><ul><ul><li>Present in virulent strains that grow in a cord like pattern </li></ul></ul></ul><ul><ul><ul><li>It inhibits migration of leukocytes </li></ul></ul></ul><ul><ul><ul><li>Causes chronic granulomas </li></ul></ul></ul>Components of cell wall
  12. 12. <ul><li>Protein </li></ul><ul><ul><li>Tuberculin reaction </li></ul></ul><ul><ul><li>Elicit formation of antibodies </li></ul></ul><ul><ul><li>Granuloma formation </li></ul></ul><ul><li>Lipopolysaccharides (Lipoarabinomannan LAM) </li></ul><ul><ul><li>Inhibition of macrophage activation by IFN </li></ul></ul><ul><ul><li>Release of cytokines (TNF  ) from macrophages which causes fever, weight loss and tissue damage </li></ul></ul>
  13. 13. Cell Wall Structure
  14. 14. Mycobacterium tuberculosis (AFB)

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