To evaluate characteristics and prognostic factors of community-onset bloodstream infection (Co-BSI) in elderly patients (≥65 years).

Analysis of a prospective series of Co-BSI at a tertiary hospital (2005–2011). Predictors of 30-day mortality were established by logistic regression analysis.

A total of 2605 episodes of Co-BSI were identified and empirical antibiotic treatment was inappropriate in 404 (15.5%). Thirty-day mortality was 11.4% and was independently associated with age (75–84 years OR 1.9, 1.37–2.67; ≥85 OR 2.85, 1.93–4.21), previous hospitalization (OR 1.45, 1.05–2.00), a fatal underlying disease (OR 2.81, 2.10–3.76), neutropenia (OR 2.62, 1.54–4.43), absence of fever (OR 1.99, 1.26–3.12), shock (OR 7.96, 5.83–10.89), inappropriate empirical treatment (OR 1.49, 1.03–2.16), isolation of Staphylococcus aureus (methicillin-resistant OR 2.83, 1.38–5.78; methicillin-susceptible OR 3.24, 1.98–5.32), enterococci (OR 2.02, 1.14–3.59) or Enterobacteriaceae resistant to third-generation cephalosporin (3GCR-E) (OR 1.96, 1.16–3.32) and having endovascular non-catheter (OR 4.64, 2.51–8.59), abdominal (OR 3.65, 2.12–6.27), skin/soft tissue (OR 3.48, 1.90–6.37), respiratory (OR 2.80, 1.75–4.50) or unknown (OR 1.83, 1.17–2.87) source.

Age is a prognostic factor and appropriateness of empirical treatment is the only modifiable variable. S. aureus, enterococci and 3GCR-E may be the microorganisms with major prognostic significance; hence efforts should be made to improve their management.