pathogenesis and toxigenicity part 1

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mame727
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241609
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pathogenesis and toxigenicity part 1
Updated:
2013-10-20 00:07:27
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patho toxi part
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part one of pthogenesis and toxigenicity
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  1. What are enterotoxins that are part of exotoxins?
    are exotoxins that specifically target the intestinal mucosa.

    • affect the camp levels
    • result in increased elimination of water from intestinal cells
    • cause voimiting and diarrhea
  2. What are the categoiries of exotoxins and what are the categories based on?
    scac

    • 1. superantigens
    • 2. cytotoxins: type i-v
    • 3. ab toxins
    • 4. cytolytic toxins.

    based on the secretion method that the bacteria uses to export the protein out of the cell.
  3. Why are cytotoxins called cytotoxins?
    where is the toxin secreted?
    what are the advantages to cytotoxins?
    are cytotoxins membrane damaging/pore formin cytotoxins?
    what gram stain is used?
    do they inhibit protein synthesis and allow ca to escape from host cells?
    the action on the toxin is within the cytoplasm

    toxin is secreted directly into the cytosol in a contact-dependent manner

    • Efficiency: poson enters only the target cell.
    • selective: intracellular target is specific

    • yes, membrane damaging and pore forming cytotoxins
    •  
    • yes, inhibit host cell protein synthesis and allow ca to escape from host cells
  4. What is the mechanism of action for cytotoxins and what kind of gram stain bacteria uses that method?
    toxin is injected directly into the cytoplasm of the host cell

    used by g- bacteria

    • molecular syringes that resemble flagella (type 3)
    • molecular syringes that resemble conjugative pili(type iv)
  5. What do ab toxins stand for?

    What are the mechanisms of action?

    are they covalently or noncovalently joined to each other?

    when are they cleaved and activated?
    • Toxin enters without the aid of the bacteria 
    • Active Binding

    • A domain/ subunit- transferred across the plasma membrane into the host cell
    • enters the cytoplasm and enzymatically acts on host targets.

    • B domain/subunit- binds to cell surface receptors of host.
    • helps to translocate the a domin/subunit.

    yes, they are covalently joined but can be not joied

    before entrance to host cell  and cleaved and activated by enzymes inside the host cell and at the plasma membrane of the host.
  6. Whow are ab toxins organized?

    when do binary toxins interac at the host membrane?
    single ab protein- diptheria toxin

    one a
    subunit + multiple b = cholera toxin

    2 a 1 b subunit= tripartite toxins or anthrax toxin

    • Binary toxins
    • before entry
  7. What is Diphtheria toxin produced by besides the Ab toxin?

    what does the a sub-unit inhibit?

    what does c. diphtheriae activate?

    What age group is it for nd what does it affect?
    corynebacterium diphtheria

    a sub inhibits protein synthesis by the host cell by blocking the transfer of an amino acid from the trna to the polypeptide.

    elongation factor 2 (ef2)

    childhood disease and it affects the respiratory system.
  8. What is botulin that is produced by Clostridium botulinum?

    How is it the most potent biological toxin?
    group of seven related 1a + 1b subunits of ab toxins.

    bind to pre-synatptic membranes of stimulatory motor neurons found at the neuromuscular junciton.

    blocks the release of acetylcholine preventing muscles fro mreceiving an excitatory signal and therefore no contraction.
  9. What is tetanospasmin that is produced by clostridium tetani?
    what does it target?
    how does it target motor neurons?
    tetanospasmin

    • motor neurons
    • is transported to the spinal column and binds to ganglioside lipids of inhibitory neurons which produce glycine which stops release of acetylcholine which causes muscles to contract.

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