Risk factors for carbapenem-resistant Acinetobacter baumannii (CRAB) infections in critically ill patients with previous CRAB colonization. A multicentre cohort study

Background . Among multidrug-resistant bacteria, carbapenem-resistant Acinetobacter baumannii (CRAB) is a major concern due to the limited therapeutic options. Objectives. The study aimed to identify such predictors to aid in the clinical management of critically ill patients. Methods. We conducted a multicenter prospective study in Italy, enrolling patients with CRAB colonization who were admitted to Intensive Care Units (ICUs) between 2020 and 2023. Multivariable logistic regression analysis was performed to identify potential risk factors for CRAB infection. To account for competing risks, we used the Cumulative Incidence Function (CIF) and Fine-Gray regression analysis, providing an accurate assessment of the risk of CRAB infection. Additionally, a logistic regression model was performed to estimate the impact of different type of critically ill patients on the risk of infection. Results. 564 colonized patients were included, and 381 (67.5%) developed a CRAB infection in ICU. In Fine-Gray model, timing to colonization ≤12 days from ICU admission [HR 1.74 (95% CI: 1.42-2.11, p<0.001), multisite colonization [HR 1.34 (1.08 -1.68), p=0.009], Charlson Comorbidity Index (CCI) ≥3 [HR 1.26 (1.01-1.58), p=0.041], male gender [HR 1.43 (1.12-1.81), p=0.004], and mechanical ventilation [HR 1.20 (0.98-1.47), p=0.072] were independent predictors of CRAB infection. In logistic regression model, COVID-19 [OR 2.31 (1.30-4.10), p=0.004] and burn patients [OR 4.84 (1.65-14.17), p=0.004] were risk factors for CRAB infection. Conclusions. Early colonization from ICU admission, multisite colonization, CCI, mechanical ventilation, and male gender are key risk factors for CRAB infection. These factors support clinicians in the management of critically ill patients with prior CRAB colonization.