The impact of Acinetobacter baumannii infections on outcome in trauma patients: A matched cohort study

Abstract

To determine the impact of Acinetobacter baumannii infection on the outcome of trauma patients. A retrospective 1:2-matched cohort study. Level I trauma intensive care unit patients with confirmed Acinetobacter baumannii infection were defined as cases. Thirty-one Acinetobacter baumannii patients were matched to 62 controls with evidence of infection caused by other microorganisms. There were 12 matching criteria, including focus of infection, demographics, severity, and characteristics of injury. In-hospital mortality rate, intensive care unit length of stay, and complications of Acinetobacter baumannii including multidrug-resistant strains in patients were compared to those of their controls; 81% had hospital-acquired pneumonia, 13% had bloodstream infections, and 6% had urinary tract infections in both groups. Acinetobacter baumannii cultures were multidrug resistant in 42% (13/31) of cases. The initial empirical antibiotic therapy was adequate in 71% (22/31). Although the in-hospital mortality was higher in the Acinetobacter baumannii group (16% vs. 13%; odds ratio, 1.23; 95% confidence interval, 0.38-4.36; p = .67), the difference did not reach statistical significance. Using the test of equivalence or clinical indifference, the impact of an Acinetobacter baumannii infection on mortality is inconclusive. This applies also to multidrug-resistant strains. Overall intensive care unit stay was prolonged for Acinetobacter baumannii when compared to controls (median, [range], 28 [7-181] days vs. 17 [2-130] days, respectively; p = .05). ARDS and acute liver failure were more frequent in the Acinetobacter baumannii group compared to the control group (35% vs. 15%; odds ratio, 3.24; 95% confidence interval, 1.17-5.48; p = .02 and 26% vs. 10%; odds ratio, 3.25; 95% confidence interval, 3.25-10.40; p = .04). In this single-center experience, Acinetobacter baumannii infection, including multidrug-resistant strains, has inconclusive impact on mortality in a cohort of trauma patients. Larger studies are needed to support a definite conclusion. Acinetobacter baumannii infection was, however, associated with a longer intensive care unit stay and a higher rate of organ failure.