Impact of early appropriate antimicrobial therapy on survival in Acinetobacter baumannii bloodstream infections

The impact of appropriate empirical antimicrobial therapy for Acinetobacter baumannii bacteraemia on patient outcomes has not been clearly established. We assessed predictors of 30-day mortality and the effect of inappropriate empirical antimicrobial treatment on mortality among patients with A. baumannii bacteraemia between July 2005 and June 2008. Initial empirical antimicrobial therapy was considered to be appropriate if the initial antibiotics that were administered within 48 h after the acquisition of a blood culture sample included at least one antibiotic that was active in vitro and when the dosage and route of administration were in accordance with current medical standards. Overall, 103 patients with nosocomial A. baumannii bacteraemia were included in the study. Appropriate empirical therapy was administered to 41.7% of patients within 48 h. The overall mortality rate was 54.4%, with rates of 39.5% and 65% for patients who received appropriate and inappropriate antimicrobial therapy within 48 h, respectively. Thus, a 25.5% reduction in the overall crude mortality rate was associated with adequate early empirical antimicrobial therapy. Multivariate analysis using a Cox regression model showed that significant independent risk factors for mortality were delayed appropriate treatment [hazard ratio (HR)=2.4, 95% confidence interval (CI) 1.3-4.2; P=0.004], development of septic shock (HR=2.6, 95% CI 1.4-4.8; P=0.004), age>65 years (HR=2.1, 95% CI 1.2-3.7; P=0.007) and mechanical ventilation (HR=3.3, 95% CI 1.5-7.4; P=0.003). It is concluded that a delay in receiving appropriate antimicrobial therapy had an adverse influence on clinical outcome in patients with A. baumannii bacteraemia.