Admission Status Is Not Destiny: Serial Surveillance Reveals Ecologic and In-Hospital Drivers of Carbapenem-Resistant Enterobacterales Colonization in Critical Care

Background: Identifying risk factors for gastrointestinal CRE colonization and acquisition is essential for guiding infection prevention and control strategies; however, most studies focus exclusively on colonization at hospital admission.Aim: We aimed to distinguish determinants of CRE colonization present at intensive care unit (ICU) admission from those driving acquisition during ICU stay using serial surveillance screening.Methods: A prospective cohort study was conducted in two ICUs in Brazil.Screening relied on rectal swab cultures from April 2022-May 2024, supplemented with immunochromatographic testing in one ICU and polymerase chain reaction in the other during October 2023-May 2024.Colonization at admission and incident acquisition during stay were outcomes of interest.Pre-ICU predictors were evaluated using logistic regression with LASSO selection, while post-ICU factors were assessed through generalized estimating equations.Findings: Among 751 patients, 39 (5%) were colonized with CRE at ICU admission.Previous acute care hospitalization (Odds Ratio (OR) 2.70; p = 0.006) and transfer from another hospital (OR 2.62; p = 0.046) were independent risk factors.Post-ICUadmission incident CRE colonization was associated with ICU B stay (OR 2.20; p = 0.013), broad-spectrum antibiotics (OR 1.90; p = 0.018), urinary catheter use (OR 2.33; p = 0.024), and shock (OR 1.91; p = 0.043).Hand hygiene compliance and Contact Precautions adherence were >80% across both units.Conclusion: CRE acquisition in ICU appears related to colonization pressure, antibiotic disruption, and specific device use.Prevention of CRE acquisition in high-prevalence ICUs likely requires interventions beyond to standard infection prevention and control measures.