This is a dangerous bug. We take it very seriously as there is a high mortality rate associated with infection - upwards of 20% in all comers with bacteremia (in hospital).Risk factors for complications include a longer duration of bacteremia, the route and site of infection, if there are indwelling devices (prosthesis, lines), and host factors (eg. immunocompromised hosts like HIV,). Metastatic spread of S. aureus is more common in those who acquire the infection in the community rather than in hospital. Also, most patients will have an identifiable source of infection, however those that do not have a greater likelihood of metastatic spread.
How do we predict complications? Good question. There is a greater probability of complications with the following risk factors:
1. If blood cultures are positive over 48 hours after admission.
2. If the patient is still febrile over 72 hours after admission.
3. If skin findings suggestive of acute infection are present.
4. If the infection was community acquired.
4. If the infection was community acquired.
If patients have 0/4 of these risk factors then there is about a 15% chance of complications, compared to a 90% chance if 4/4 of these risk factors are positive.
Okay...so what are we worried about? What are the complications?
1. Infective Endocarditis. We will discuss this in detail later, but I have written a bit about it here.
2. Seeding of other sites: S. aureas can go anywhere, but it has a particular predilection for the vertebral column (osteomyelitis), joints (septic arthritis), the spleen (splenic abscesses), skin and soft tissue (can cause myositis or necrotising fasciitis), lungs (in those with right sided endocarditis like IV drug users), veins (septic thrombophlebitis if an IV or other catheter in place), intracardiac hardware (pacemakers, ICD's), and orthopedic hardware.
3. Sepsis
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