Characteristics of Staphylococcus aureus Bacteraemia and Predictors of Early and Late Mortality

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.