Outcome of inadequate empirical antibiotic therapy in emergency department patients with community-onset bloodstream infections.

BACKGROUND: Studies on the effect of inadequate empirical antibiotic therapy on the outcome of patients with systemic infection have led to inconsistent results.
METHODS: We analysed data from a comprehensive clinical database collected prospectively in a university hospital between 2008 and 2009. All adult patients who registered in the emergency department (ED) with a bloodstream infection (BSI) were enrolled. Empirical therapy was considered adequate if it included antimicrobials to which the specific isolate displayed in vitro susceptibility and that were administered within 24 h of ED admission. The propensity score (PS) was created by a logistic regression model predicting inadequate empirical therapy. PS-adjusted multivariate analysis was performed by the Cox regression model. The Mortality in Emergency Department Sepsis (MEDS) score was used for the adjustment of residual confounding due to differences in the baseline clinical severity of disease.
RESULTS: Out of 937 episodes of bacteraemia, 255 (27.2%) patients received inadequate empirical antimicrobial therapy. A crude analysis showed that inadequate antibiotic therapy was associated with higher mortality rates (hazard ratio 1.78, 95% CI 1.30-2.45). PS-adjusted multivariate analyses also showed a significant adverse impact (hazard ratio 1.59, 95% CI 1.14-2.28). The clinical disease severity significantly modified the effect of inadequate antibiotic therapy on survival. The magnitude of the adverse impact of inadequate antibiotic therapy decreased with the increasing severity of sepsis (P=0.009).
CONCLUSIONS: Inadequate empirical antimicrobial therapy for community-onset BSI was associated with higher 30 day mortality rates. Study populations with different clinical severities may have different results, which may help to partly explain the heterogeneous findings in many similar studies.