Predictors of mortality in Acinetobacter baumannii bacteremia

This study retrospectively investigated 149 episodes of Acinetobacter baumannii bacteremia which occurred during a 41-month period from September 1997 to January 2001. Bacteremia was nosocomial in 139 (93%) of the episodes and community-acquired in 10 (7%). Thirty three deaths (22.1%) were attributed to these episodes of A. baumannii bacteremia. The mean age of survivors was younger than that of patients who died of bacteremia (60.4 +/- 19.9 vs 67.1 +/- 17.4) but this result was not significant on univariate analysis (p=0.084). Previous intensive care unit stay was longer among survivors than among patients who died of bacteremia (9.5 vs 18 days, p=0.048). Factors associated with mortality included immunosuppression (p=0.019), shock (p=0.002), recent surgery (p=0.008), invasive procedures such as central venous catheterization (p=0.002), urinary catheterization (p=0.012), placement of a nasogastric tube (p<0.001), pulmonary catheterization (p=0.015), and mechanical ventilation (p=0.035). The number of underlying conditions (p=0.015) and invasive procedures (p<0.001) were positively correlated with mortality. Mortality was significantly associated with lower platelet count (p=0.001) and lower serum albumin concentration (p=0.005). Patients with catheter-related bacteremia had a high survival rate (96.2%), while survival rate was low in patients with infection originating from the respiratory tract (60.8%). Susceptibility testing by agar dilution test indicated that imipenem was the most effective antibiotic, followed by cefepime and ciprofloxacin. The mortality rate was lower in patients who received 1 or more antibiotics to which the isolates were susceptible, but this difference was not significant (p=0.197). On multivariate analysis, factors that independently correlated with mortality were increased age (p=0.003), immunosuppressive status (p=0.001), recent surgery (p=0.002), acute respiratory failure (p=0.004), acute renal failure (p=0.009) and septic shock (p<0.001). These findings highlight the importance of a treatment strategy based on risk stratification among patients with A. baumannii bacteremia.