We aimed to describe the characteristics of patients with Staphylococcus aureus bacteremia and to evaluate the risk factors associated with early (7-day) and late (30-day) mortality. We performed an observational study including all consecutive episodes of Staphylococcus aureus bacteremia diagnosed at two Italian university hospitals during 2010±2014. A total of 337 patients were included. Mean age was 69 years (range, 57±78) and 65% were males. Methicillin-resistant S. aureus (MRSA) was identified in 132/337 (39%)cases. Overall 7-And 30-day mortality were 13% and 26%, respectively. Early mortality was associated with increased Charlson scores (OR 1.3, 95% CI 1.1±1.5), MRSA bacteremia (OR 3.2, 95% CI 1.4±8.1), presentation with septic shock (OR 13.5, 95% CI 5.4±36.4), and occurrence of endocarditis (OR 4.5, 95%CI 1.4±14.6). Similar risk factors were identified for late mortality, including increased Charlson scores (OR 1.2, 95% CI 1.1±1.4), MRSA bacteremia (OR 2.1, 95% CI 1.2±3.9), presentation with septic shock (OR 4, 95%CI 1.7±9.7), occurrence of endocarditis (OR 3.8, 95% CI 1.4±10.2) as well as Child C cirrhosis (OR 3.9, 95% CI 1.1±14.4) and primary bacteremia (OR 2.5, 95%CI 1.3±5). Infectious disease consultation resulted in better outcomes both at 7 (OR 0.1, 95% CI 0.05±0.4) and at 30 days (OR 0.4, 95% CI 0.2± 0.7). In conclusion, our study highlighted high rates of MRSA infection in nosocomial Staphylococcus aureus bacteremia. Multiple comorbidities, disease severity and methicillin-resistance are key factors for early and late mortality in this group. In patients with Staphylococcus aureus bacteremia, infectious disease consultation remains a valuable tool to improve clinical outcome
