Identification and phylogenetic analysis of a Brucella canis Isolate from an aborted canine fetus.

Brucella canis is an important veterinary pathogen with growing public health concerns, but it remains neglected. In this study, a B. canis strain (BMNM19) was characterized using bacteriological culture, biotyping, whole-genome sequencing single nucleotide polymorphism analysis (WGS-SNP). Bacteriological examination revealed rough, grayish-white, sticky, dry, and opaque colonies, and conventional biotyping confirmed it as B. canis, which posing risks to humans in contact with infected dogs. Genomic analysis showed that BMNM19 shares 99.99 % average nucleotide identity (ANI) with the reference strain B. canis ATCC 23365. The strain was found to carry an mprF resistance gene and 69 virulence-associated genes, shared 2829 core genes with other reference strains, and displayed no unique genes. In silico MLST assigned BMNM19 to sequence type ST21. Phylogenetic based on core genome SNPs revealed that BMNM19 is closely related to B. canis strains from Zhejiang, Jiangsu Province (China), Japan and South Korea. These results expand our understanding of the genetic diversity of B. canis in northern, China and emphasize its persistent zoonotic threat to dogs and humans in close contact. This study provides critical molecular insights into the epidemiology of B. canis, to underscore the need for strengthened public health surveillance of this emerging zoonotic pathogen.