Global multi-host genomic epidemiology of Acinetobacter baumannii reveals transmission at one health interfaces.

Acinetobacter baumannii is one of the most important antibiotic-resistant bacterial pathogens. While human clinical isolates have been extensively studied, genomic information from non-human sources remains limited. Here, gathering a dataset of > 23,000 genomes from many sources, we provide a comprehensive view of non-human A. baumannii. Average Nucleotide Identity (ANI) and Sequence Type (ST) diversity analyses show that non-human isolates are more diverse than the human isolates. Furthermore, the non-human isolates have an open pangenome. Notably, phylogenomic tree and population structure analysis suggest constant transmission between humans and non-human sources, with source-specific lineages. Finally, resistome analysis reveals that bacteria from diverse sources, such as dogs, horses, and wastewater, carry significant numbers of antibiotic resistance genes (ARGs). Together, these results suggest that non-human A. baumannii are vastly diverse and may pose a public health concern, stressing the need for more research on non-human sources of bacterial pathogens through an explicit One Health surveillance approach. On a more general level, this work highlights the relevance of multi-host genomic epidemiology approximations to better understand important human pathogens.