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13 Cards in this Set
- Front
- Back
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The production of which enzyme differentiates Staph from Strep?
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Catalase
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Which Staph species forms bubbles when mixed with H2O2?
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Staph. aureus. catalase degreades peroxide (H2O2) into H2O and O2 gas causing bubbles to form.
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Describe the appearance of Staph under the microscope.
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Gram+ irregular grape like clusters.
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Where is Staph aureus most often found?
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Nose. Serves as community or hospital acquired methicillin resistant S. aureus(MRSA)
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What 5 features differentiate S aureus from other species of Staph?
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Coagulase positive
mannitol fermentation beta hemolytic protein A Exotoxins |
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What is protein A and where is it found?
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Virulence factor in the cell wall of S. aureus which binds to the fc portion of immunoglobulin G(igG) preventing activation of complement, opsonization and phagocytosis.
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What other two important cell wall virulence factors does S. aureus possess/
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Teichoic acid and polysaccharide capsule
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What are the three most clinically important exotoxins produced by S. aureus?
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Enterotoxin, toxic shock syndrome toxin(TSST) exfoliatin.
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Which toxin is associated with food poisoning causing vomiting and watery nonbloody diarrhea?
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Enterotoxin. Food poisoning is self limitimg, lasting app. 2 hours.
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Which foods are associated with S. aureus food poisoning/
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Mayonnaise, potato salad and custard.
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Which S. aureus toxin act as a superantigen and what do they do?
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Enterotoxin and TSST. Activates a subpopulation of T cells with the V-beta receptor subtype leading to a massive cytokine response.
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Which cytokines are released by superantigens and what is the clinical result/
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Interleukin-1(IL-1) and IL-2, tumor necrosis factor(TNF) leading to systemic shock, and DIC and organ failure.
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What is the mechanism od action of exfoliatin?
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Cleaves desmoglein in desmosomes causing separation of the epidermis.
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