Comparative genomics reveals avian Acinetobacter baumannii as antimicrobial resistance reservoirs and bovine strains with elevated pathogenicity

Multidrug-resistant Acinetobacter baumannii is primarily known as an opportunistic nosocomial pathogen but is increasingly recognized as an emerging contaminant in foods of animal origin. In the present study, we characterized the A. baumannii strains from raw meat samples and undertook a comparative genomic analysis to explore the resistome, virulome, mobilome (integrons and transposons) and pathogenic potential of the A. baumannii strains from food animals and animal origin foods. Avian strains of A. baumannii were found to carry a significantly higher number of antimicrobial resistance genes (P < 0.05) and also possess mobile genetic elements (transposons, integrons), while bovine strains were found to possess significantly higher pathogenic potential (P < 0.05) than A. baumannii strains from other sources. Pan-genome and pan-resistome analyses indicated an open nature for both across all sources. Phylogenetic analysis revealed spatial clustering of the isolates, and isolates sequenced in the present study clustered closely with Chinese isolates. Taken together, being the first comparative genomic study on A. baumannii strains from food animals and foods of animal origin, the present study provided insights into the genomic features of A. baumannii strains while highlighting the potential role of avian strains of A. baumannii in the dissemination of antimicrobial resistance through animal origin foods.