Genomic insights into the population structure, antimicrobial resistance, and virulence of <i>Brachyspira hyodysenteriae</i> from diverse geographical regions

<i>Brachyspira hyodysenteriae</i>, the primary causative agent of swine dysentery, remains a less-studied pathogen than other bacterial species that impact animal health. This study uses whole-genome sequencing and advanced phylogenomic approaches to reveal the genetic diversity and geographical distribution of <i>B. hyodysenteriae</i> isolates, focusing on U.S. populations. The identification of nine distinct phylogenetic lineages and associated sublineages highlights the pathogen's complex population structure and regional variation. Importantly, the study detects AMR genes, including <i>tva</i>(A) and <i>lnu</i>(C), linked to tiamulin and lincomycin resistance, that may pose significant challenges to disease management. The analysis also identifies virulence-associated genes, shedding light on molecular mechanisms underlying pathogenicity. By combining core-genome SNP phylogenies with multilocus sequence typing and accessory genome insights, this work provides a robust framework for a better understanding of <i>B. hyodysenteriae</i> evolution. Overall, these findings underscore the importance of genomic surveillance in informing control strategies and improving swine health worldwide.