Microbiology Chapter 15

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aji
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118006
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Microbiology Chapter 15
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2011-11-20 12:59:36
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Description:
Microbial Mechanisms of Pathogenicity
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  1. An organisms ability to cause a disease is called it’s
    pathogenicity.
  2. The degree of pathogenicity is called it’s
    virulence.
  3. In order for a microorganism to cause disease it must:
    • Gain access to the host
    • Adhere to the host tissues
    • Penetrate or evade the hosts defenses
    • Damage tissues and cause disease
  4. The way in which a pathogen gains entrance to a host is called its
    portal of entry.
  5. portal of entry are :
    • Mucus Membranes:Respiratory tract,GI tract,Genitourinary tract,Conjunctiva
    • Skin:Parenteral route
  6. Many organisms have a preferred portal of entry which is a prerequisite to a ___
    disease
  7. Preferred Portal of Entry - Salmonella typhi
    • digestive system (disease )
    • skin (no disease)
  8. Preferred Portal of Entry - Streptococcus
    • respiratory system (disease)
    • Digestive system (no disease)
  9. Preferred Portal of Entry - Bacillus anthracis
    more than one
  10. How virulent a microbe is expressed in terms of its ___
    LD50 : number of microbes in a dose which will kill 50% of test animals injected
  11. The dose required to produce a demonstrable infection is indicated by ___
    ID50
  12. LD50 & ID50 are used to ___
    compare virulence of organisms to each other
  13. Portal of entry - Bacillus anthracis ID50
    • Skin : 10-50 Endospores
    • Inhalation : 10,000-20,000 Endospores
    • Ingestion : 250,000-1,000,000 Endospores
  14. Which organisms is the most virulent?
    The lower the LD50 the more virulent the organism or toxin is.
  15. Most pathogenic bacteria cause disease by penetrating tissues not by
    simply attaching to them
  16. Several factors that contribute to an organisms ability to invade a tissue :
    • Capsules
    • Cell wall components
    • Enzymes
  17. M protein resists phagocytosis eg ___
    Streptococcus pyogenes
  18. Opa protein inhibits T helper cells eg ___
    Neisseria gonorrhoeae
  19. Mycolic acid (waxy lipid) resists digestion eg ___
    Mycobacterium tuberculosis
  20. Organism which Prevent phagocytosis
    • Streptococcus pneumoniae
    • Haemophilus influenzae
    • Bacillus anthracis
  21. ___ Coagulates fibrinogen
    Coagulase
  22. ___ Digest fibrin clots
    Kinases
  23. ___ Hydrolyzes hyaluronic acid
    Hyaluronidase
  24. ___ Hydrolyzes collagen
    Collagenase
  25. ___ Destroy IgA antibodies
    IgA proteases
  26. If a pathogen overcomes a hosts defenses it can damage tissues in four basic ways :
    • 1 Direct Damage
    • 2 Production of Toxins
    • 3 Induction of hypersensitivity reactions
    • 4 Using the hosts nutrients
  27. To obtain free iron some pathogen secretes proteins called ___
    siderophores
  28. ___ are poisonous substances produced by certain microorganisms
    Toxins
  29. The capacity of an organism to produce a toxin is called its ___
    Toxigenicity.
  30. ___ is a condition of toxins in the blood
    Toxemia
  31. ___ is inactivated toxin used in a vaccine
    Toxoid
  32. ___ Antibodies against a specific toxin
    Antitoxin
  33. There are two types of toxins ___ & ___
    • 1 Exotoxins
    • 2 Endotoxins
  34. Source of exotoxin is ___
    Mostly Gram +
  35. Exotoxin is the byproduct of ___
    growing cells
  36. Exotoxin is made up of ___
    Protein
  37. Exotoxin causes fever y/n ?
    No
  38. Exotoxin is nutralized by antitoxin y/n ?
    yes
  39. LD50 of Exotoxin
    Small
  40. Main 6 Exotoxin representative
    • 1 Diphtheria toxin
    • 2 Erythogenic Toxin
    • 3 Botulinum toxin
    • 4 Tetanus toxin
    • 5 Vibrio enterotoxins
    • 6 Staphylococcal enterotoxins
  41. Source of Endotoxins
    Gram -tive
  42. Endotoxins' relation to microbes
    outer membrane
  43. Endotoxins chemistry
    Lipid A
  44. Endotoxins causes fever y/n?
    yes
  45. Endotoxins is nutralized by Antitoxin y/n?
    No
  46. LD50 of Endotoxins
    Relatively Large
  47. ___ are small circular pieces of DNA separate from the main chromosome which are capable of independent replication.
    Plasmids
  48. ___ Can be transferred between organisms
    • Resistance factors
    • Virulence factors
  49. ___ are bacteria viruses
    Bacteriophages
  50. Bacteriophages can incorporate their DNA into the host-Lysogeny by ___
    Lysogenic conversion
  51. Viruses avoid a hosts immune response by ___
    • 1 They grow inside cells
    • 2 Specialized attachment
    • 3 Some attack the immune system itself
  52. ___ visible effects of viral infection
    Cytopathic effects
  53. Those that result in cell death are called ___ effects
    cytocydal
  54. Those that damage the cell but do not kill it are called ___ effects
    non-cytocydal

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