Risk factors for carbapenem-resistant <i>Acinetobacter baumannii</i> (CRAB) infections in critically ill patients with previous CRAB colonization: a multicentre cohort study

Abstract Background Among MDR bacteria, carbapenem-resistant Acinetobacter baumannii (CRAB) is a major concern due to the limited therapeutic options. Objectives To identify predictors to aid in the clinical management of critically ill patients. Methods We conducted a multicentre prospective study in Italy, enrolling patients with CRAB colonization who were admitted to 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 types of critically ill patients on the risk of infection. Results We included 564 colonized patients, and 381 (67.5%) developed a CRAB infection in the ICU. In the logistic regression model, multisite colonization (OR 2.78; 95% CI: 1.90–4.08; P < 0.001), Charlson comorbidity index (CCI) ≥3 (OR 1.59; 95% CI: 1.00–2.50; P = 0.047), mechanical ventilation (OR 1.48; 95% CI: 1.00–2.18; P = 0.048), male gender (OR 2.06; 95% CI: 1.38–3.10; P < 0.001), and time from ICU admission to colonization ≤12 days (OR 2.00; 95% CI: 1.36–2.94; P < 0.001) were independent predictors of CRAB infection. Findings were confirmed in the Fine–Gray model. In a secondary model, COVID-19 (OR 2.31; 95% CI: 1.30–4.10; P = 0.004) and burn patients (OR 4.84; 95% CI: 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.