Microbiology Lecture 6

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Microbiology Lecture 6
2010-09-29 14:40:52

Mechanisms of Bacterial & Viral Pathogenesis
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  1. 3 factors important for bacterial survival
    • food
    • accessibility (adherence/colonization)
    • escape clearance (immune system)
  2. Normal Flora
    • a type of bacterial growth
    • usually found in GI tract, mouth, skin and upper respiratory tract
    • aid in digestion of food, vitamin production & protection from pathogens
    • can cause disease if invading a normally sterile area
  3. Opportunistic Pathogen
    normally harmless, but can cause disease when immuno-defense is lowered
  4. Virulent bacteria
    growth occurs at expense of host
  5. bind specific receptors or sugars on tissue surface (e.g cell surface, fimbriae)
  6. bacteria bound within sticky web of polysaccharide that binds cells to each other and to a surface
    (exists wherever surfaces contact water)
  7. Bacterial effector proteins pass through needle into host cell
    Type III Secretion
  8. Name some virulence factors
    • Capsule
    • adhesins
    • toxins
    • degradative enzymes
    • cell wall
    • membrane components
  9. Exotoxins
    found in both GM + and Gm-
  10. Endotoxins
    • Only ound in Gm- (in LPS)
    • stimulates release of cytokines and prostoglandins
    • can cause fever, shock or death
  11. Mechanisms of escaping host defense
    • capsule
    • intracellular growth
    • antigentic variation
  12. Susceptibility & severity of disease from a viral infection depend on
    • mechanisms of exposure/ site of infection
    • hosts immune status, age and health
    • viral dose
    • genetics of virus and host
  13. Transport of a virus in the blood is called
  14. A viral infection can either result in one of 3 outcomes. They are:
    • failed infection
    • lytic infection (host cell death)
    • persistent infection ( viral replication without cell death)
  15. Levels of Cell Supsceptibility (3)
    • Nonpermissive cell- expresses antiviral mechanism
    • Permissive cell- supports complete replicative cycle
    • Semipermissive cell- may support some, but not all steps in replication
  16. Two types of viral infection
    • lytic
    • nonlytic
  17. Apoptosis
    • "cell suicide"
    • can facilitate viral release from cell, but limits viral production
  18. What is Syncytia formation
    Fusion of neighboring cells into multi-nucleated giant cells triggered by surface glycoproteins

    Allows spread of virus and escape from antibody detection