Card Set Information

2011-11-14 17:48:08

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  1. Group Stuctures
    • Gram positive cocci
    • form clusters
    • Produce catalase
  2. Organism
    • Produces coagulase -> binds to prothrombin, causing clots in plasma
    • Coagulase test for staph
  3. Toxins
    • Alpha-toxin - pore forming, similar to complement
    • Exfolatin - only some strains -> epidermal splitting
    • SuperAg: Enterotoxins -> GI symptoms, heat/pH stable, act on neura receptors; TSST -> direct toxic effects on endothelial cells -> cap leakage/shock
  4. Epidemiology
    • Basic human habitat - nares
    • Most are autinfections
    • Nosocomial outbreaks: virulent strain
  5. Pathogenesis
    • Usually not virulent
    • A protein - binds to fibronectin
    • Alpha toxin produces injury
    • Injury leads to inflammation -> boil
    • Can lead to bacteremia and internal organ/bone infection
    • TSST: produces during active infection, can be absorbed systemically from local infection
  6. Clinical manifestations
    • Primary Dx: furuncle/boil - superficial skin infection in sebacious gland/hair follicle
    • Usually resolves spontaneously
    • Cna cause blood stream invasion
    • Impetigo: usually secondary invader with GAS
    • Deep lesions: 90% of osteomyolitis are caused by S. Aureus
  7. S. Aureus toxin syndroms
    • Scalded skin syndrome: produced by exfolatin, usually in neonates and kids under 5. Can't isolate S. Aureus from lesions
    • TSS: high fever, vomiting, diarrhea, sore throat, muscle pain -> shock w/ renal/hepatic damage; blood cultures usually negative
    • Food poisoning: vomiting/diarrhea w/in 5 hours of eating
  8. Diagnosis
    • Aerobic blood agar culture
    • Catalase/coagulase tests
  9. Treatment
    • Most boils resolve on own
    • Penicillin G still works for some strains
    • Pencillin resistant penicillins and cephalosprins still used
    • MRSA -> vancomycin and erthromycin
    • Action of MRSA: pencillinase, alteration in peptidoglycan transpeptidases
  10. Coagulase negative staph
    • S. epidermis
    • Prosthetic devices
    • Some produce slime that sticks to plastics