Nosocomial bacteremia involving Acinetobacter baumannii in critically ill patients:: a matched cohort study

Objective: To determine outcome and attributable mortality in critically ill patients with nosocomial bacteremia involving A. baumannii. Design: A retrospective matched cohort study in which all ICU patients with microbiologically documented A. baumannii bacteremia were defined as cases. Matching of the controls was based on equivalent APACHE II score ( 2 points) and diagnostic category. Control patients were required to have an ICU stay equivalent to or longer than the case prior to onset of the bacteremia. Setting: The 54-bed ICU of the 1060-bed Ghent University Hospital. Patients: 45 ICU patients with A. baumannii bacteremia and 90 matched control subjects without clinical or n-microbiological evidence of blood stream infection. Measurements: Population characteristics and in-hospital mortality rates of patients with A. baumannii bacteremia and their controls were compared. Attributable mortality is determined by subtracting the crude mortality rate of the controls from the crude mortality rate of the cases. Results: Patients with A. baumannii bacteremia had significantly more hemodynamic instability, longer ICU stay, and longer length of ventilator dependence than controls. In-hospital mortality rates for cases and controls were, respectively, 42.2% and 34.4%; thus the attributable mortality was 7.8%. Conclusion: In critically ill patients A. baumannii bacteremia is not associated with a significantly increased mortality rate.