Prevalence and Antimicrobial Resistance of Enterobacteriaceae in Wild Birds Across Europe: A Systematic Review.

Wild birds are increasingly recognized as reservoirs and vectors of antimicrobial-resistant (AMR) Enterobacteriaceae, but comprehensive assessments across Europe remain limited. AMR represents a growing threat to global health under the One Health framework. Background/Objectives: This review aimed to evaluate the occurrence, diversity, and resistance patterns of Enterobacteriaceae in wild birds across Europe (1969-2025), and to identify ecological and methodological trends. Methods: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, we searched PubMed and Web of Science until July 2025. Inclusion criteria targeted studies reporting Enterobacteriaceae isolation and/or AMR in free-living European birds. Data were synthesized thematically by bacterial species, avian order, resistance profile, and country. Risk of bias was assessed based on sampling, reporting, and diagnostic clarity. Results: Eighty studies met the inclusion criteria, covering over 18,000 wild birds from 25 countries. Escherichia coli and Salmonella enterica were most reported, often exhibiting resistance to β-lactams, fluoroquinolones, and tetracyclines. AMR was detected in birds from both urban and natural areas. Study designs varied widely, with inconsistent methods for bacterial identification and susceptibility testing. Conclusions: Wild birds in Europe carry resistant Enterobacteriaceae, including strains with clinically relevant resistance profiles. These findings support their inclusion in One Health AMR surveillance and highlight the need for harmonized protocols, expanded molecular tools, and ecological integration.