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Staph aureus: Presentation

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Staph Aureus Presentation

  • Commonly colonizes the nares, ears, axilla, and groin 
  • Note: Staphylococcus aureus is a constituent of the normal skin flora
    • Most common cause of nosocomial (hospital-related) infections, especially with intravascular devices or IV drug use (access via skin)
  • Inflammatory disease
    • Skin infections
      • E.g. impetigo, cellulitis, skin abscesses
    • Pneumonia
      • causes superimposed bacterial pneumonia on viral infections 
    • Acute endocarditis
      • Common in IV drug users
      • Tricuspid valve is usually affected
      • Patients may develop multiple septic emboli in lungs, which can cause pulmonary infarcts
    • Septic arthritis
      • Most common cause of septic arthritis
      • More common in IV drug users 
    • Osteomyelitis
      • Adhesion to collagen is the main virulence factor of Staphylococcus aureus in osteomyelitis. 
      • Most common cause of osteomyelitis overall
  • Toxin-mediated disease
    • Toxic shock syndrome (TSST-1)
      • TSST-1 is a superantigen that crosslinks MHC II and T-cell receptor, resulting in polyclonal T-cell activation
      • fever, vomiting, rash, desquamation, shock, end-organ failure
        • Toxic shock syndrome (TSS) is caused by Staphylococcus aureus. TSS presents with fever, vomiting desquamation, and hypotension.
      • TSS results in ↑ AST, ↑ ALT, ↑ bilirubin. 
      • Associated with prolonged use of vaginal tampons or nasal packing
      • Compare with Strep pyogenes TSS: toxic shock-like syndrome associated with painful skin infection 
    • Scalded skin syndrome (exfoliative toxin)
      • Exfoliative toxin destroys keratinocyte attachments in the stratum granulosum
      • Typically seen in newborns, children, adults with renal insufficiency 
    • Gastroenteritis/food poisoning (enterotoxin)
      • Preformed enterotoxin
        • Heat stable, not destroyed by cooking
      • Short incubation period (2- 6 hr), followed by vomiting and abdominal cramps (more common) and diarrhea (rare)
      • associated with consumption of certain precooked foods, dairy products, custard, and mayonnaise that sits at room temperature for an extended period of time (e.g. picnic, potluck)