Microbiology - 0412 - Bacterial pathogenesis

  1. Survival plot
    Kaplan-Meier plot
  2. Steps involved in bacterial pathogenesis
    • Colonization
    • migrate
    • tissue or cellular destruction
    • dissemination
    • The cycle repeats with colonization again
    • During this process, the bacteria has to evade the host immune system, always happening at every step
  3. Colonization
    • Nonspecific
    • Usually mediated by polysaccharides, sugars, Biofilms
    • don’t discriminate between surfaces
    • Specific
    • Pili bind to specific receptors
    • Serve as adhesins for binding to certain proteins on the host cell surface
  4. Tissue destruction:
    enzymes that degrade the extracellular matrix: Collagenases, proteases, toxins
  5. Dissemination
    sugar hydrolases: Allow bacteria to escape the biofilm
  6. Evasion of host response
    Half of the genome deals with the host immune system
  7. Initial hose response
    • macrophage phagocytosing the pathogen, forming phagosome, fuses with lysosome
    • Lysosome has a damaging environment:
    • Low pH
    • Superoxide radicals
    • lysosomal hydrolases
    • Phagocyte also displays things to the rest of the immune system
  8. evade Initial hose response
    • Inhibit fusion of phagosome and lysosome: Legionella, Mycobacterium, Chlamydia
    • Resistance to lysosomal enzymes: Salmonella, some strains of Mycobacterium
    • Escape the phagosome and get into the cytoplasm, adapt to cytoplasmic replication: Listeria, Rickettsia
  9. Legionella pneumophila
    causes pneumonia, respiratory disease
  10. Legionella pneumophila
    • 1. phagosome
    • 2. prevents fusion of lysosome by Mediates the formation of the membrane of the ER around the phagosome, forming a triple-layered membrane
    • 3. breaks down ER membrane, products triggers the bacteria to replicate within the single membrane bound structure and produce flagella
    • 4. burst from the cell and spread to other cells, dissemination
  11. Listeria monocytogenes
    Causes disease listeriosis
  12. Listeria monocytogenes
    • 1. invades a cell via phagosome
    • 2. lyses the phagosome,
    • 3. divides in the cytosol
    • 4. takes actin filaments, coats itself with this and uses this to push itself out into neighboring cell
    • 5. enveloped by two membranes: One from the original cell, and another from the new cell
    • 6. the cycle continues
    • the mechanism prevents the bacteria from getting into contact with the immune system
  13. Other mechanism
    produce Ig protease to break dowm antibody
Card Set
Microbiology - 0412 - Bacterial pathogenesis
Microbiology - 0412 - Bacterial pathogenesis