Wednesday, October 1, 2008

Day #93 - Staphylococcus Aureus Bacteremia

Today we talked about a patient who presented with a febrile gastrointestinal illness who happened to have two diagnoses. First, a probable viral gastroenteritis acquired from his daycare aged son. Second, a concomitant staphylococcus aureus bacteremia.

I wanted to talk about the management of Staphylococcus Aureus Bacteremia. There is a good article here on the management of MRSA bacteremia.

  • Never treat staphylococcus aureus in the blood as a contaminant. Like fungus in the blood, this always needs to be treated!
  • The *minimum* treatment duration is 14 days (intravenous). This is for uncomplicated infections only.
    • Risk factors for complication:
      • Longer duration of illness
      • Community acquired infection
      • Persistent fever at 72h (OR 2)
      • Persistent positive blood culture at 96h (OR 5)
      • Hemodialysis patients
      • Indwelling lines or other prosthetic material
      • MRSA
      • No identifiable source for the bacteremia (i.e. no skin or line focus)
      • Blood cultures positive within 14 hours of drawing them
  • You need to exclude bacterial endocarditis. Present in 10-13% of cases...
  • Can also cause pacemaker and AICD infections
  • Vertebral osteomyelitis
  • Septic arthritis
  • Splenic abscess (persistant fever, LUQ pain)
  • Septic thrombophlebitis (particularly with lines)
  • Septic pulmonary emboli
  • Brain abscess/meningitis/mycotic aneurysms
  • Skin/soft tissue abscesses


Treatment:
  • Ideal treatment for MSSA is with a beta-lactam like cloxacillin or cefazolin. These are superior head to head with vancomycin for the treatment of MSSA.
  • Removable foci should be removed if feasible and practical to do so
  • Duration depends on complications. IE 4-6 weeks. Osteo ~6 weeks.
Risk of Death
  • 20 to 40%!
  • Age
  • MRSA (OR 9.3)
  • Blood cultures positive less than 12 hours (OR 7)
  • Complication (OR 9)


In medicine we often attempt to find one unifying diagnosis that explains all symptoms -- in satisfying what is known as Occam's Razor.

The important teaching point in a complicated case like this is that the patient may have multiple diagnoses and that we must keep an open mind. In response to Occam's Razor, Hickam's Dictum states that "[the patient] can have as many diseases as the damn well please".

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