Bacterial Pathogens Causing Ventilator-Associated Pneumonia in Mechanically Ventilated Children: A Systematic Review and Meta-Analysis.

BACKGROUND: Ventilator-associated pneumonia (VAP) remains a major healthcare-associated infection in pediatric and neonatal intensive care units (PICUs and NICUs). The microbiological etiology of pediatric VAP varies considerably across geographic regions, and a comprehensive global quantitative synthesis spanning both PICU and NICU settings using modern quality appraisal frameworks is lacking. OBJECTIVES: To estimate the global pooled prevalence of individual bacterial pathogens causing VAP in mechanically ventilated children and to characterize the burden of multidrug-resistant (MDR) organisms. METHODS: Following PRISMA 2020 guidelines and a prospective International Prospective Register of Systematic Reviews (PROSPERO)-registered protocol, we searched MEDLINE/PubMed, Scopus, Cochrane CENTRAL, and Web of Science for studies published between January 2015 and December 2025. Studies reporting bacterial pathogens isolated from children (0-18 years) on invasive mechanical ventilation for >= 48 hours were eligible. Pooled prevalence proportions and 95% confidence intervals (CIs) were estimated using the DerSimonian-Laird random-effects model after logit transformation. Subgroup analyses were performed by data reporting type (patient-based versus isolate-based). The certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. RESULTS: Eighteen studies encompassing 1,524 VAP episodes across 13 countries were included. Gram-negative bacteria predominated, with a pooled prevalence of 76.30% (95% CI: 65.55-84.49%; I² = 93.0%). Gram-positive bacteria accounted for 13.73% (95% CI: 8.85-20.69%; I² = 88.2%). The most frequent individual pathogens were Pseudomonas aeruginosa (19.7%; 95% CI: 14.3-26.5%; I² = 86.4%) and Klebsiella spp. (18.8%; 95% CI: 12.8-26.9%; I² = 89.5%), followed by Acinetobacter spp. (9.4%), Staphylococcus aureus (7.2%), Escherichia coli (5.9%), Stenotrophomonas maltophilia (5.2%), and Enterobacter spp. (3.6%). Subgroup analysis by data reporting type revealed a borderline significant difference for P. aeruginosa (patient-based 24.4% vs. isolate-based 12.8%; p = 0.050) and a significant difference for S. aureus (patient-based 5.4% vs. isolate-based 13.6%; p = 0.022). The pooled prevalence of MDR pathogens was 23.47% (95% CI: 14.88-34.97%; I² = 89.3%). According to the GRADE assessment, the certainty of evidence was low for most outcomes due to high statistical heterogeneity and study limitations. CONCLUSIONS: Gram-negative bacilli, particularly P. aeruginosa and Klebsiella spp., overwhelmingly dominate the global microbiological landscape of pediatric VAP. The substantial prevalence of MDR organisms, coupled with low certainty of global evidence, underscores an urgent need for institution-specific empiric antibiotic protocols and robust antimicrobial stewardship in pediatric critical care units worldwide.