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16 Cards in this Set
- Front
- Back
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How does Staph. aureus cause disease?
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S. aureus causes disease by producing toxins and by multiplying in tissue and causing inflammation.
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What is the typical lesion of S. aureus?
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An abscess. They drain to the outside after undergoing central necrosis.(furuncles and boils)
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What are the three clinically important exotoxins?
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enterotoxin/toxic shock syndrome/ exfoliatin.
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What does enterotoxin cause?
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Causes food poisoning characterized by prominent vomiting and watery, nonbloody diarrhea.
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How does enterotoxin behave?
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It acts as a superantigen within the GI tract to stimulate the release of large amounts of interleukin 1 and 2 from macrophages and helper T cells, respectively.
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What causes the vomiting?
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It is caused by cytokines released from lymphoid cells, which stimulate the Enteric nervous system to activate the vomiting center.
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Is enterotoxin resistent?
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Yes.. It is fairly heat resistent and is usually not inactivated by brief cooking. It resists stomach acid and to GI enzymes. There are 6 types, A-E subtypes.
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What is toxic shock syndrome?
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TSST causes toxic shock, especially in ampon using menstruating women, or individuals with wound infection.
It can also occur from nasal packing to stop epistaxis. |
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TSST is produced locally by S. aureus in either the vagina, nose or other infected site. TRUE/FALSE
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TRUE. The toxin enters the blood. Blood cultures generally do not grow S. aureus.
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How does TSST cause toxic shock?
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It is a superantigen and causes TSST by stimulating the release of large amounts of IL-1, IL-2 and tumor necrosis factor(TNF). It occurs in people with no antibody titer.
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What does exfoliatin cause?
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It causes "scalded skin syndrome" in young children. It is epidermolytic and acts as a protease that cleaves desmoglein in desmosomes, leading to the separation of the epidermis at the granular cell layer.
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Which toxins can kill leukocytes?
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Leukicidins, which can as well cause necrosis in tissues.
Alpha toxin, is one which causes necrosis of the skin and hemolysis. |
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The cytotoxic effect of alpha toxin is attributed to what?
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It is attributed to the formation of holes in the cell membrane and the consequent loss of low molecular weight substances from the damaged cell.
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List some of these toxic enzymes.
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Coagulase
fibrinolysin hyoluronidase proteases, nucleases lipases |
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What does coagulase do?
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By clotting plasma, serves to wall off the infected site, thereby delaying the migration of neutrophils into the site.
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What does Staphylokinase do?
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IT is a fibrinolysin that lyses thrombi.
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