Genetic diversity of Mycoplasma bovis isolated from bovine respiratory disease and bovine mastitis in Chile

Abstract

Mycoplasma bovis, a major bacterial pathogen for cattle, is responsible for diseases such as pneumonia, mastitis, otitis, and arthritis, leading to substantial economic losses and animal welfare concerns. Despite its wide global distribution, there is limited information in South America. M. bovis has been reported as a mastitis agent in Chile, but its genetic diversity is poorly understood. Therefore, this study aimed to determine the genetic diversity of M. bovis isolates from Chilean dairy cattle (from bovine respiratory disease and mastitis cases) in the last two decades and evaluate their genetic relatedness with strains isolated in different countries using a whole genome sequencing approach. The M. bovis population in Chile was found to be highly homogeneous, with MLST and phylogenomic analysis identifying ST60 as the dominant clone, representing most of the isolates (97.8 %), while just one isolate was typed as ST12 (2.2 %). Phylogenomic analysis revealed close genetic relatedness among most Chilean isolates, showing a close genetic relationship with North American strains, forming a tight clade with Canadian ST60 strains, while the single Chilean ST12 isolate clustered with North American, Israeli, and European strains and clustered with the type strain (PG45) of this species. Moreover, the pangenome analysis confirms that M. bovis has an open pangenome, with a large range of accessory genes that remain largely unexplored and may hold key insights into its genome plasticity, thereby opening future research. The findings of this study provide the first insights into the Chilean population structure of M. bovis, contributing to the global epidemiology of this pathogen with a focus on South America. These results also open future research focused on the comprehensive characterization of this dominant clone, inspiring the scientific community to further exploration into the genetic diversity of M. bovis in Chile.