Risk factors for and impact of carbapenem-resistant Acinetobacter baumannii colonization and infection: matched case-control study

The objective of this investigation was to identify risk factors for carbapenem-resistant Acinetobacter baumannii (CRAB) and its association with mortality. A population-based matched case-control study using the computerized database of Clalit Health Services (CHS) in the period between 2007 and 2012 was conducted. Hospitalized patients with CRAB colonization or infection were compared to hospitalized patients without evidence of A. baumannii, matched by age, ward of hospitalization, season, Charlson score, and length of hospitalization. Risk factors for CRAB isolation were searched for using multivariate analysis. Association of CRAB and other risk factors with mortality were assessed in the cohort. A total of 1190 patients with CRAB were matched to 1190 patients without CRAB. Low socioeconomic status was independently associated with CRAB isolation and CRAB bacteremia [odds ratio 2.18, 95 % confidence interval (CI) 1.02-5]. Other risk factors were invasive procedures and bacteremia with other pathogens prior to CRAB isolation, and various comorbidities. Among all patients, CRAB isolation was independently associated with increased mortality (hazard ratio 2.33, 95 % CI 2.08-2.6). Socioeconomic status is associated with health outcomes. Our population-based study revealed an almost doubled risk for CRAB in patients at lower socioeconomic status and an association with healthcare exposure. CRAB was associated with mortality and might become a risk indicator for complex morbidity and mortality.