Hospital-Acquired Bloodstream Infections in Relation to Intensive Care Unit Stays During Hospitalization—A Population-Based Cohort Study

<b>Background:</b> Little is known about the clinical characteristics and pathogens causing hospital-acquired bloodstream infections (HA-BSIs) in relation to an intensive care unit (ICU) stay. <b>Methods:</b> Population-based cohort study, comprising 35% of the Danish population, 2009-2016. We derived four patient groups with first-time HA-BSIs: no ICU stay during the admission (non-ICU patients) and HA-BSI acquired before, in, or after an ICU stay (before-ICU, in-ICU, and after-ICU patients). These groups were compared in relation to microbiological and clinical characteristics, including 28- and >28-day mortality. <b>Results:</b> Among 6888 HA-BSI patients, 4017, 792, 1388, and 691 were non-ICU, before-ICU, in-ICU, and after-ICU, respectively. The rates of several microorganisms differed between the patient groups, e.g., Enterococci (9.4% of non-ICU and 32.0% of in-ICU patients). The 28-day mortality was 26.3% in non-ICU, 45.0% in before-ICU, 35.6% in in-ICU, and 19.0% in after-ICU patients. The corresponding adjusted hazard ratios (95% confidence interval) were 2.10 (1.85-2.36), 1.67 (1.50-1.87), and 0.76 (0.63-0.91) (reference: non-ICU patients). There were few differences as regards >28-day mortality. <b>Conclusions:</b> We found large differences between common microorganisms and prognosis between the four patient groups. After-ICU patients had the lowest 28-day mortality despite age and comorbidity characteristics similar to the other three groups.