Genomic insights into Brucella melitensis in India: stability of ST8 and the role of virulence genes in regional adaptations.

Brucella melitensis is a highly infectious zoonotic pathogen responsible for brucellosis, which significantly affects both human and livestock health worldwide. This study employed whole-genome sequencing (WGS) to analyze the genetic diversity of 24 B. melitensis isolates from India. Pangenome analysis revealed a highly conserved nature with the involved strains having very limited accessory genes. Multilocus Sequence Typing (MLST) identified sequence type ST8 as predominant among Indian strains. Analysis of virulence genes revealed a total of 43 virulence-related genes in all strains, emphasizing their critical role in the pathogenicity of B. melitensis. Unique gene profiles and distinct phylogenetic clusters suggest regional adaptations and evolutionary pressures. The comprehensive genomic insights from this study help to elucidate the geographic distribution and interspecies transmission of Indian strains, highlighting the importance of targeted brucellosis control measures in India. Additionally, the identification of conserved virulence genes involved in immune evasion and intracellular survival highlights their importance in the bacterium's pathogenicity. This research contributes to the global understanding of B. melitensis genomic diversity, providing valuable insights for broader epidemiological studies and brucellosis management strategies worldwide.IMPORTANCEB. melitensis is a significant cause of illness in both humans and animals, particularly in India, where the disease remains a major concern. This study highlights that only a few genetic types of the bacteria are circulating in the region, which means control efforts can be better focused on these specific types. By understanding the unique characteristics of Indian strains, and how these strains spread and adapt, this research offers valuable guidance for improving brucellosis prevention strategies. These insights can help in developing more effective diagnostic tools, enhancing vaccination efforts, and strengthening disease control programs to reduce the impact of brucellosis on public health and livestock industries.