A multicenter study of risk factors and outcome of hospitalized patients with infections due to carbapenem-resistant Acinetobacter baumannii

Background: Risk factors and outcome in patients who acquire nosocomial infections due to carbapenem-resistant Acinetobacter baumannii (CRAB) are rarely investigated. Methods: A multicenter retrospective study was conducted to analyze the clinical and microbiological data of patients with nosocomial infections due to A. baumannii in 10 hospitals around Taiwan from May 2004 to December 2006. Comparisons were made between patients with infections due to CRAB and patients with infections due to carbapenem-susceptible A. baumannii (CSAB). Results: One hundred and twenty-one patients carrying CRAB (infections, n= 91) and 127 patients carrying CSAB (infections, n= 97) were recruited for analysis. Compared with patients with CSAB infections, patients with CRAB infections had a longer duration of hospital stay before A. baumannii was isolated (median 48 vs. 21 days, p< 0.001) and were more likely to have had exposure to a carbapenem (adjusted odds ratio (AOR) 2.57, 95% confidence interval (95% CI) 1.43-5.35; p= 0.02) and an intensive care unit (ICU) stay (AOR 3.42, 95% CI 1.76-5.26; p=0.008). Risk factors associated with CRAB bacteremia included duration of hospital stay before onset of bacteremia (AOR 1.009 per 1-day longer, 95% CI 1.03-1.24; p= 0.049), prior colonization with A. baumannii (AOR 3.27, 95% CI 1.99-5.93; p= 0.002), and hospitalization in the ICU (AOR 6.12, 95% CI 1.58-13.68; p= 0.009). Patients with CRAB bacteremia had a higher mortality rate than patients with CSAB bacteremia (46.0% vs. 28.3%, p= 0.04). Multivariate analysis showed that carbapenem resistance (AOR 5.31, 95% CI 1.88-13.25; p= 0.002), central venous catheterization (AOR 3.27, 95% CI 1.55-10.56; p= 0.009), and ICU stay (AOR 2.56, 95% CI 1.15-8.85; p= 0.04) were independent variables associated with mortality in patients with A. baumannii bacteremia. Conclusions: Patients with CRAB infections have a higher mortality rate than those with CSAB infections. Longer hospital stay, colonization with A. baumannii, and admission to the ICU were associated with the development of CRAB bacteremia.