Healthcare-associated vs. hospital-acquired Staphylococcus aureus bacteremia

Objective: To analyze clinical features and outcomes of patients with hospital-acquired (HA) and healthcare-associated (HCA) Staphylococcus aureus bacteremia. Methods: A retrospective cohort study was conducted from 1988 to 2007. We compared patients with clinically significant HA with those with HCA S. aureus bacteremia. Risk factors for 30-day all-cause mortality were assessed using multivariable logistic regression analysis. Cox regression analysis was used to estimate the hazard ratio (HR) for 5-year mortality with 95% confidence intervals (CI). Results: Of 1261 episodes, 735 (58.3%) were HA and 526 (41.7%) were HCA. The percentage of MRSA was 48.2% (354/735) in HA vs. 42.2% (222/526) in HCA bacteremia; p= 0.04. The percentages of HCA S. aureus bacteremia and MRSA bacteremia did not vary throughout the study period. Mortality at 30 days was 40.2% (507/1261) and at 1 year was 63.4% (800/1261); this was comparable for HA and HCA bacteremia. Five-year survival curves in both settings followed very similar patterns (HR 1.01, 95% CI 0.89-1.15). Risk factors for 30-day mortality were similar, except for primary bacteremia and pre-existing heart valve disease in the HA group. Conclusions: HCA S. aureus bacteremia shares many similarities with HA bacteremia with respect to the prevalence of MRSA strains, mortality rates, and risk factors for death, and should be managed similarly.