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13 Cards in this Set

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