Epidemiology and Outcome Determinants of Staphylococcus aureus Bacteremia Revisited: A Population-Based Study

Abstract

Purpose: Staphylococcus aureus bacteremia (SAB) is associated with significant morbidity and mortality. We sought to re-define the burden, epidemiology and mortality-associated risk factors of SAB in a large Canadian health region.

Methods: Residents (> 18 years) experiencing SAB from 2012 to 2014 were assessed. Incidence rates were calculated using civic census results. Factors associated with 30-day mortality were determined through multivariate logistic regression. Incidence and risk factors for SAB were compared to 2000-2006 data.

Results: 780 residents experienced 840 episodes of SAB (MRSA; 20%). Incidence rates increased from 23.5 to 32.0 cases/100,000 from 2012 to 2014; [IRR 1.15 (95% CI 1.07-1.23); p < 0.001]. Compared to a decade ago, incidence of SAB has increased [IRR 1.28 (95% CI 1.21-1.36); p < 0.001] despite minimal change in nosocomial SAB. MRSA proportion did not change through the study (p = 0.3), but did increase relative to a decade ago (20.0% vs 11.0%, p < 0.001). Thirty-day mortality rates were 30.6% and 21.3% for MRSA and MSSA, respectively (p = 0.01), similar to rates from 2000 to 2006. Several clinical, demographic, and biochemical factors were independently associated with SAB mortality.

Conclusions: SAB is common within our population resulting in significant mortality. Incidence rates of SAB are increasing in our health region; however, 30-day mortality rates remain stable.

Keywords: Bacteremia; Epidemiology; MRSA; Mortality; Staphylococcus aureus.