Pathogenicity

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Author:
Strawberrylotus
ID:
301877
Filename:
Pathogenicity
Updated:
2015-05-01 01:54:11
Tags:
CH16
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CH16
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  1. Pathogen portals of entry
    • Mucous membranes
    • Respiratory tract
    • Gastrointestinal tract
    • Genitourinary tract
    • Conjuctiva
    • Skin
    • Parenteral route
  2. Pathogen portals of exit
    the same as the portals of entry
  3. Penetration of skin
    • Via cut or scratch
    • Via vector (flea, mosquito, ect.)
    • Through hair follicles or sweat -glands
  4. Penetration of mucous membranes
    • Uptake by epithelial cells
    • Uptake by APC's
  5. Which is a more common route of infection
    skin
  6. Establishment of Infection
    • 1. Adherence 
    •      • Adhesions allow microbes to bind to specific cell types

    2. Infection; growth of microbe

    • 3. Damage to host
    •      •Invasion of tissues 
    •      •Toxins
  7. Evasion of Host Defenses
    • Hiding within host cell
    • Evasion of complement
    • Evasion of phagocytosis
    • Exoenzymes
    • Avoiding antibodies
    • Antigenic variation
  8. Pathogens prevent encounters with the phagocyte
    • C5a peptidase
    • Cytolytic toxins
  9. Pathogens avoid recognition and attachment by
    • Capsules
    • M protein
    • Fc receptors
  10. Pathogens survive within the phagocyte
    • Escape from the phagosome
    • Prevent phagolysosome fusion
    • Survive within the phagosome
  11. Avoiding Opsinizing Antibodies
    • Protein A on the antigen
    • Fc portion of igG is not available for receptor
  12. Exoenzymes - Extracellular Enzymes
    •Coagulase – clots fibrinogen in the blood

    • •Kinases – digest clots to allow spread of
    • microbe. Ex: streptokinase

    •Collagenase – breaks down collagen
  13. mechanisms of pathogenicity
    •Using host’s nutrients

    •Direct damage by invasion

    •Producing toxins

    •Inducing hypersensitivity reactions
  14. Exotoxins
    • gram positive bacteria
    • Secreted by living bacteria
    • Usually a protein
    • Can vaccinate using toxoids
  15. Endotoxin
    Released by dying bacteria and can occur in any gram negative bacteria

    Derived from LPS from Gram negative cell wall
  16. Categories of Exotoxins
    1.A-B toxins

    2.Membrane-damaging toxins

    3.Superantigens

    4.Other exotoxins
  17. LD50
    Lethal Dose for 50% exposed

    • A measurement to compare potency of
    • different toxins
  18. LD50 2
    –LD50 for Botulinum toxin = 0.03 ng/kg

    –LD50 for Staphylococcal enterotoxin = 1350 ng/kg
  19. A-B Exotoxins
    Have 2 protein parts: A and B

    B – binds host cell

    A – has toxin function
  20. A-B Exotoxins -Neurotoxins
    damage nervous system

    Ex:  Botulinum toxin
  21. A-B Exotoxins - Enterotoxins
    cause intestinal symptoms

    Ex:  Cholera toxin
  22. A-B Exotoxins - Cytotoxins
    lyse cell or interfere with cell function

    Ex:  Diphtheria toxin
  23. Membrane-Damaging Toxins
    Disrupt plasma membranes. results in host cell lysis

    •Pore-formation

    •Phospholipases
  24. Pore-formation
    Streptococcus pyogenes - streptolysin O –  

    Staphyloccus aureus - beta-hemolysin
  25. Phospholipases
    Clostridium perfringins – causes gas gangrene
  26. Superantigens
    Bind T cell receptors. triggers massive cytokine release

    Non-specific, mass-activation of T cells
  27. Superantigens 2
    Staphylococcus - toxic shock syndrome
  28. Endotoxin
    •LPS - lipopolysaccharide-

    –Active portion – Lipid A

    •Source of endotoxin – Gram negative bacteria (OM)
  29. Endotoxin Reasons for release
    Cell lysis

    –Bacteria die

    –Bacteria killed by the immune system

    –Bacteria killed by antibiotics
  30. Effects of Endotoxin
    Damage associated with inflammation
  31. LPS activates both innate and adaptive responses
    Macrophages --> release cytokines --> fever & inflammation

    B cells --> non-specific activation
  32. Antibiotic treatment can
    worsen the effects of endotoxin
  33. Septic Shock
    endotoxin in large amounts triggers systemic inflammation & blood clotting proteins
  34. DIC
    Disseminated intravascular clotting - a disorder in which there is an over activation of blood clotting in the blood vessels and resultant bleeding within the body
  35. Portal of Exit For Microbes
    Allow for spread of infection
  36. Portal of Exit For Microbes 2
    •Bodily Secretions

        –Mucous; sneezing & coughing

        –Feces

        –Semen & vaginal secretions

    •Blood

    •Skin shedding
  37. What do you do with all the information generated by identification methods???
    •Organize it

    • •Want to be able to run as few tests
    • possible in order to quickly identify organisms

    •All of the information is used to create: Dichotomous Keys

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