Although brucellosis is endemic to the Qinghai–Tibet Plateau, the molecular epidemiology of circulating Brucella abortus is still poorly characterized. Thus, in this study, we adopted an integrated approach of bacteriology and whole‐genome sequencing (WGS) to genetically characterize B. abortus isolates from sheep, yak, and cattle in Qinghai, China. Conventional biotyping assays and multilocus sequence typing (MLST) show that the three strains were conclusively identified as B. abortus biovar 1, sequence type 2 (ST2). Furthermore, average nucleotide identity (ANI) analysis indicated that the three strains (BA0611, BAHYS, and BAQHM) showed ANI values above 99.99% and over 99.91% identity with the B. abortus reference strain, confirming their species assignment. The three B. abortus isolates BA0611, BAHYS, and BAQHM exhibited identical virulence gene profiles, harboring 69 virulence‐related genes altogether and uniformly lacking three crucial virulence‐associated genes, namely bmaA , btpB , and virB10 . Core‐genome SNP phylogenetic analysis revealed close genetic relatedness to Tibetan strain XZ19‐1 and Russian isolates, distinguishing them from previously identified local human and marmot strains. The high genetic similarity observed among the three strains indicates a common source of infection, supporting the classification of these cases as a cluster infection. These data together confirm the prevalence of genetically divergent B. abortus lineages within the Qinghai–Tibet Plateau, which enriches current insights into the host spectrum and genomic diversity of this zoonotic pathogen in the region. These findings provide robust support for optimizing local genomic surveillance and formulating precise prevention and control strategies to reduce brucellosis prevalence in both animal and human populations.
Cao et al. (Thu,) studied this question.