Clinical Outcomes of Carbapenem-Resistant Acinetobacter baumannii Bloodstream Infections: Study of a 2-State Monoclonal Outbreak

OBJECTIVE: To characterize the clinical outcomes of patients with bloodstream infection caused by carbapenem-resistant Acinetobacter baumannii during a 2-state monoclonal outbreak. DESIGN: Multicenter observational study. Setting. Four tertiary care hospitals and 1 long-term acute care hospital. METHODS: A retrospective medical chart review was conducted for all consecutive patients during the period January 1, 2005, through April 30, 2006, for whom 1 or more blood cultures yielded carbapenem-resistant A. baumannii. RESULTS: We identified 86 patients from the 16-month study period. Their mortality rate was 41%; of the 35 patients who died, one-third (13) had positive blood culture results for carbapenem-resistant A. baumannii at the time of death. Risk factors associated with mortality were intensive care unit stay, malignancy, and presence of fever and/or hypotension at the time blood sample for culture was obtained. Only 5 patients received adequate empirical antibiotic treatment, but the choice of treatment did not affect mortality. Fifty-seven patients (66.2%) had a single positive blood culture result for carbapenem-resistant A. baumannii; the only factor associated with a single positive blood culture result was the presence of decubitus ulcers. Interestingly, during the study period, a transition from single to multiple positive blood culture results was observed. Four patients, 3 of whom were in a burn intensive care unit, were bacteremic for more than 30 days (range, 36-86 days). CONCLUSIONS: To our knowledge, this is the first time a study has described 2 patterns of bloodstream infection with A. baumannii: single versus multiple positive blood culture results, as well as a subset of patients with prolonged bacteremia.