Respiratory microbiota signatures as a predictor of ventilator-associated pneumonia in hospitalised children with severe bronchiolitis

Abstract Objectives Ventilator-associated pneumonia (VAP) is a significant complication in pediatric patients with severe bronchiolitis undergoing mechanical ventilation (MV) in pediatric intensive care units (PICUs). The role of respiratory microbiota in VAP development remains underexplored in this vulnerable population. This study aimed to characterize respiratory microbiota in critically ill children with severe bronchiolitis receiving critical care and identify microbial patterns associated with VAP. Methods We conducted a cohort study in paediatric patients with severe bronchiolitis requiring MV at a tertiary PICU in Catalonia, Spain. Epidemiological, clinical and microbiological data were collected. Respiratory microbiota was assessed using 16S rRNA gene sequencing of nasopharyngeal (NP) aspirates and bronchoalveolar lavage (BAL) samples obtained before and during MV. Results Baseline NP microbiota differed significantly between VAP and non-VAP groups, with overrepresentation of Moraxella, Enterobacter , and Amniculibacterium genera and underrepresentation of Prevotella in patients who developed VAP. BAL microbiota showed fewer differences, although Enterobacter was more abundant in VAP cases. Random forest models demonstrated strong predictive performance, with the model integrating NP microbiota and clinical parameters achieving the highest accuracy (AUC 0.956). Conclusions Specific nasopharyngeal microbial signatures, combined with clinical factors, may serve as risk markers for VAP in mechanically ventilated children, potentially guiding targeted prevention strategies in PICUs.