Risk factors for the development of hospital-acquired pneumonia in patients with carbapenem-resistant Acinetobacter baumannii respiratory colonization and the role of multisite colonization: a multicenter retrospective study

Abstract

INTRODUCTION: Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are associated with high morbidity and mortality rates. Furthermore, the role of CRAB respiratory colonization, including multisite colonization, has not yet been adequately highlighted in critically ill patients. MATERIALS AND METHODS: In this retrospective multicenter study, conducted in 4 different Italian hospitals, patients with CRAB respiratory colonization +/- other site who developed or did not develop clinically significant pneumonia from December 2015 to December 2023 were enrolled. The primary objective of the study was to identify risk factors associated with the development of pneumonia. RESULTS: 760 patients were enrolled; among them, 392 (51.5%) developed pneumonia, while 304 (39.9%) patients presented multisite colonization. Overall, in-hospital mortality was 76.3% with a higher mortality (79.6%) in patients who developed pneumonia (p = 0.033). In logistic regression analysis, factors associated with the development of pneumonia included: age, immunosuppressive therapy, COPD, ventilatory support and multisite colonization. A score was developed with AUC 0.72, CI95% 0.68-0.75, p < 0.001 and a sensitivity of 79% and specificity of 55% with a score > 2 and a maximum score of 10 points. Multisite colonization was recorded more frequently in patients who developed pneumonia (51%, p < 0.001). Finally, Kaplan-Meier curves showed a significantly reduced survival at 30 days (p = 0.005) and throughout the hospital stay (p = 0.002) in patients with multisite colonization. CONCLUSIONS: This study highlights the risk factors associated with the development of pneumonia in patients already colonized by CRAB. Multisite colonization showed an important role as a risk factor for the development of pneumonia and for its correlation with mortality. CLINICAL TRIAL NUMBER: Not applicable.