The purpose of this study is to determine how monocyte HLA-DR and other markers of immune function change with time in patients with and without prior immune dysfunction who survive sepsis from Staphylococcus aureus bacteremia.

We hypothesize that patients with prior immune dysfunction will have greater reductions in HLA-DR and other markers of immune function after an episode of sepsis than people who do not have prior immune dysfunction.

Inclusion Criteria:

• At least one blood culture positive for S. aureus

• Patients aged ≥18 years

• At least two of four systemic inflammatory response syndrome (SIRS) criteria on the day of positive blood cultures. SIRS criteria are:

  • Body temperature less than 36°C(96.8°F) or greater than 38°C(100.4°F)
  • Heart rate greater than 90 beats per minute
  • Tachypnea (high respiratory rate), with greater than 20 breaths per minute; or, an arterial partial pressure of carbon dioxide less than 32 mmHg
  • WBC less than 4000 cells/mm³ (4 x 109 cells/L) or greater than 12,000 cells/mm³ (12 x 109 cells/L); or the presence of greater than 10% immature neutrophils (band forms)

Exclusion Criteria:

• Sequential Organ Failure Assessment (SOFA) score > 12 on day of positive blood cultures
• Survival expected to be < 7 days from positive blood cultures

Hospital inpatients with Staphylococcus aureus bacteremia who are over 18 years old.