Quiz 11 Micro

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bamerb07
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49978
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Quiz 11 Micro
Updated:
2010-11-16 16:41:03
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Svinth Micro
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Svinth Micro Quiz 11
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  1. Pathogenesis
    • A microbe capable of causing disease is a pathogen
    • Virulence: measure of pathogenicity (in terms of degrees)
  2. How Do Microbes Make us Sick?
    • Many microbes have to gain access to host
    • Cause damage to host tissues
    • Sometimes microbial wastes cause disease
    • Some microbes don’t need to enter to cause disease (e.g. dental caries, acne)
  3. Portals of Entry
    • Ways to get inside host
    • Mucous membranes
    • Skin
    • Parenteral route (under the skin)
  4. Mucus membranes
    • Respiratory tract
    • Gastrointestinal tract
    • Genitourinary tract
    • Conjunctiva (in eye)
  5. Respiratory Tract
    • Preferred Site
    • Easiest Portal of Entry
    • Inhalation of dust/droplets
    • Common cold, pneumonia, tuberculosis, influenza, measles, smallpox
  6. Gastrointestinal Tract
    • Food/water contamination
    • Contaminated fingers
    • HCl/bile/enzymes take care of most microbes
    • Some survive
    • Poliomyelitis, shigellosa, cholera
    • Pathogens are eliminated in feces
  7. Genitourinary Tract
    • Sexually transmitted diseases
    • Some can penetrate unbroken membranes
    • Others require an opening
    • HIV, HPV, chlamydia, Herpes, syphilis, gonorrhea
  8. Conjunctiva
    Conjunctivitis, trachoma, opthalmia neonatrium
  9. Parenteral Route
    • Punctures
    • Injections
    • Bites
    • Cuts
    • Wounds
    • Surgery
    • Split skin
    • HIV, Hepatitis, Tetanus, Gangrene
  10. Pathogenicity
    • Depends upon:
    • Portal of entry
    • Number of microbes introduces
    • Type of microbe introduced
    • ID50
  11. ID50
    • Infectious dose for 50% of a sample population
    • Comparative value
    • E.g: Bacillus anthracis
    • Subcutaneous: ID50=10-50 endospores
    • Inhalation: ID50=10,000-50,000 endospores
    • Gastrointestinal tract ID50=250,000-1 million endospores
  12. LD50
    • Potency of a toxin
    • Lethal dose
    • Botulinum toxin LD50=0.03 ng/kg
    • Shiga toxin LD50=250 ng/kg
    • Staph enterotoxin LD50= 1350 ng/kg
  13. Adherence
    • How microbe binds to host cells to gain access
    • Adhesins(ligands)/receptors
    • Pathogen/host
    • Adhesins are found on glycocalyx, pili, fimbrae, flagella (all bacterial)
    • Most studied to date are glycoproteins or lipoproteins
    • Bind to sugars on the surface of hosts (e.g. mannose)
  14. Adherence
    • Treponema pallidum (clamydia)
    • Tapered end
    • Corkscrew motion
    • Can make it’s way through mucous membrane. Doesn’t have to go through broken cells because of the specific shape.
  15. Biofilms
    • Contact lenses
    • Catheters
    • Stents
    • Heart valves
    • Hip replacement components
    • Estimate is that ~65% of human bacterial infections are due to biofilms
    • Biofilms stick bacteria to surfaces and resist antibiotics/phagocytosis
  16. How Bacterial Pathogens Penetrate Host Defenses
    • Capsule
    • Cell wall components
    • M protein
    • Opa
    • Mycolic acid
    • Enzymes (exoenzymes)
    • Coagulases
    • Bacterial kinases (fibrinolysin)
    • Hyaluronidase
    • Collagenase
    • IgA proteases
  17. Capsules
    Capsules prevent phagocytes attaching to bacteria
  18. Resistance
    • Some bacteria can live inside phagocytes without being digested!
    • Enzymes can help bacteria resist phagocytosis
  19. IgA proteases
    • Imunoglobulin (antibody)
    • IgA Abs present on mucosal surfaces
    • IgA proteases cleave antibody
    • Inactivating it
    • Line mucous membranes. They are there to grab. It is a way for macrophages to see the pathogen. Some pathogens can break this apart. It makes the pathogens form a glob which makes it easier to see.
  20. Invasins
    • Surface proteins
    • Rearrange actin filaments of host cytoskeleton
    • Membrane ruffling
    • Microbe sinks or is engulfed by host cell
  21. Antigenic Variation
    • Influenza (antigenic shift)
    • N. gonorrhoeae
    • Trypanosoma brucei gambienese

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