Carbapenem-resistant Acinetobacter baumannii in intensive care unit patients: risk factors for acquisition, infection and their consequences.

A retrospective case-control study was performed to assess risk factors and the clinical and economic consequences associated with acquisition of carbapenem-resistant Acinetobacter baumannii (CR-AB) in an intensive care unit (ICU) over a 24-month period. CR-AB was acquired by 64 of 1431 ICU admissions; each was matched with two controls. Risk factors associated with CR-AB acquisition included ICU-wide variables, such as 'colonization pressure' (the prevalence of ICU colonized patients) and ICU antibiotic use over the preceding three months, as well as patient-related variables. Among colonized patients, risk factors for CR-AB infection included transfusion and 'colonization density' (the proportion of body sites colonized with CR-AB). CR-AB infection was independently associated with increased hospital mortality [mortality difference: 20%; 95% confidence interval (CI): 1-40%], prolonged ICU stay (median length of stay difference: 15 days; 95% CI: 9-21 days) and prolonged hospital stay (30 days, 11-38 days) compared with matched controls.