Card Set Information

2012-11-27 11:12:40

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  1. Define portal of entry, pathogenicity, virulence
    • Portal of entry: specific route by which pathogens enter body
    • Pathogenicity: the ability to cause disease
    • Virulence: the extent of pathogenicity
  2. List and describe the portals of entry and explain their role in disease
    • Mucous membranes:
    • Respiratory tract - inhaled (cold, pneumonia, TB)
    • Gastrointestinal tract - food, water, hands (Hep A, amoebic dysentery, cholera, typhoid fever)
    • Genitourinary tract - STDs (AIDS, chlamydia, syphilis)
    • Skin: broken skin, natural openings [hair follicles, sweat glands] (hookworm, mycoses)
    • Parenteral: inejctions, bites, cuts, surgery (WNV, malaria)
    • Placenta: interuterine infections (rubella, toxoplasmosis)
  3. List and describe the portals of exit and explain their role in disease
    • Respiratory tract: coughing and sneezing
    • Gastrointestinal tract: feces, saliva
    • Genitourinary tract: urine and vaginal secretions
    • Skin:
    • Blood: biting arthropods, needles/syringes
  4. Describe how pathogens penetrate host defenses
    • Invasins: Salmonella induce their own uptake in epithelia cells by inducing ruffles on M cells.  Alters host actin to enter host cell.
    • Listeria uses actin to move from one cell to the next
  5. Explain how capusles and other components of the cell wall contibute to pathogenicity
    • Capsules: prevent phagocytosis (Streptococcus pneumoniae, Haemophilu influenzae, Bacillus anthracis)
    • M protein: resists phagocytosis (Streptococcus pyrogenes)
    • Opa protein: inhibits T helper cells (Neisseria gonorrhoeae)
    • Mycloic acid: (waxy lipid) resists digestion (Mycobacterium tuberculosis)
  6. Define LD50 and ID 50 and understand their value to the study of disease.
    • ID50 (infectious dose): number of microbes required to infect 50% of test population
    • LD50 (lethal dose): number of microbes required or amount of toxin needed to kill 50% of test population
  7. List and describe the mechanisms used by microorganisms to evade host defenses and give examples of each
    • Capsules/cell wall components:
    • Enzymes:
    • Siderophores - take iron from host iron-binding proteins
    • Coagulase - clots blood, protects against phagocytosis (Streptococcus, S. aureus)
    • Kinases - Digest fibrin clots, spreads infection (Streptococcus, Staphylococcus)
    • Hyaluronidase - Hydrolyzes hyaluronic acid, spreads infection (Streptococcus)
    • Collagenase - Hydrolyzes collagen, spreads gas ganagrene [tissue death] (Clostridium prefringens)
    • IgA proteases - destroy IgA antibodies (Neisseria)
    • Viral mechanisms:
    • Penetrates and growns INSIDE host cells
    • Hid their attachment sites
    • Antigenic variation - alering surface proteins to evade antibodies (Influenza, HIV)
  8. Describe how microorganisms damage host cells
    • Disrupt host cell function by using host nutrients (iron) - siderophores
    • Direct damage by pathogen, toxin, or waste products
    • Indirect damage via immune response
  9. Define and differentiate between exotoxins and endotoxins (features)
    • Exotoxins: protein biproduct of metabolism, bacterial source (mostly Gram-positive bacteria), not heat stable, high toxicity, specific for a structure or function in host cell, non-fever inducing
    • Endotoxins: Lipid A of lipopolysaccharide (in cell wall), Bacterial source (mostly Gram-negative bactera), heat stable, low toxicity, fever inducing
  10. Types of endotoxins + mechanisms of action
    • A-B toxins: proteins with two domains (Diptheria toxin, botulinum toxin, tetanus toxin)
    • A portion - active enzyme
    • B portion - binding componend (detaches after penetration)
    • Membrane-dusrupting toxins: Lyse host cells
    • Making protein channels in the p. membrane - leukocidins, hemolysins, streptolysins
    • Disrupting phospholipid bilayer
    • Superantigens: cause intense immune repsonse due to release of cytokines from T cells
  11. Describe the mechanism of action for Diptheria, Botulinum, Cholera, Tetanus, Lipid A
    • Diptheria: inhibits protein synthesis (A-B)
    • Botulinum: neurotoxin, causes flaccid paralysis (A-B)
    • Cholera: Enterotoxin, causes severe diarrhea and vomiting (A-B)
    • Tetanus: Neurotoxin, prevents relaxation of muscle (A-B)
    • Lipid A (endotoxin): Causes fever and septic shock
  12. Explain how endotoxins cause fever and shock
    • Macrophage ingests a gram-negative bacterium
    • Bacterium is decraded, releasing endotoxins that induce cytokines (IL-1 and TNF)
    • Cytokines travel to hypothalamus
    • Cytokines induce protaglandin production which "increase the body's temperature" producing fever