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15 Cards in this Set
- Front
- Back
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What are the structural components of S. aureus?
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Cell Wall - peptidoglycan interspersed w/ ribitol-teichoic acid
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Protein A
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Virulence factor - binds to Fc portion of IgG molecules and interferes w/ opsonization
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Pathogenesis - Colonization virulence determinants
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Cell-bound protein adhesins: serve as receptors for fibronectin, laminin, collagen, or sialoglycoprotein
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Pathogenesis - Invasion
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Invasins: staphylokinase, hyaluronidase
Other: proteases, lipases, nucleases, collagenase, elastases |
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Pathogenesis - Resistance to phagocytosis
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Coagulase, protein A, leukocidins, hemolysins, carotenoids, superoxide dismutase, catalases, growth at low pH
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Pathogenesis - Resistance to immune responses
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Coagulase, protein A, antigenic variation
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Pathogenesis - Toxigenesis
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Cytotoxic toxins (hemolysin and leukocidin)
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Toxins - alpha-toxin
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insert directly into the lipid bilayer of the host cytoplasmic membrane → formation of transmembrane pores → release of vital intracellular molecules → cell death
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Toxins - Exfoliatin
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disrupt intercellular junctions (intracellular splitting of epidermis between stratum spinosum and stratum granulosum)
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Toxins - Pyrogenic Toxin Superantigens (PTSAgs)
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strongly mitogenic for T cells
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Toxins - Staphylococcal enterotoxins
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cause gastrointestinal pathogenesis by directly acting on neural receptors in upper GI tract; also stimulate the vomiting center in the brain
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Toxins - Toxic Shock Syndrome Toxin (TSST-1)
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cause of staphylococcal toxic shock syndrome; has both superantigen mechanism and direct toxic effects on endothelial cells producing inflammatory mediators that induce shock
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Superantigens
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an intact protein molecule presented to by MHCII Molecules --> stimulates T cell response (via Vbeta region of TCR)--> cytokine storm of IL-1, IL-2. TNF-alpha --> Toxic shock syndrome
Inhibits induction of specific adaptive response |
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Resistance MOA
- Methicillin resistant & Vancomycin resistant |
1) Beta-lactamase production
2) Mutation of transpeptidase w/ reduced affinity to beta-lactam antibiotics |
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Treatment
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Sensitive: Nafcillin/Oxacillin
Resistant: Vancomycin or Levofloxacin + rifampin |
