Molecular determinants of pathogenicity in a Streptococcus equi subsp. zooepidemicus strain from wild boar in Russia.

Streptococcus equi subspecies zooepidemicus (SEZ) is a highly adaptable bacterial pathogen capable of interspecies transmission. Its evolutionary success is attributed to significant genetic plasticity, enabling colonization of a broad host range including horses, cattle, pigs, and humans. Streptococcus equi subsp. zooepidemicus SB1 (SEZ SB1) is a recognized cause of severe disease in various animal populations, underscoring its importance as an emerging pathogen of veterinary and potential zoonotic concern. This study provides a comprehensive characterization of a SEZ SB1 isolate obtained from a wild boar. A multi-level diagnostic strategy was employed, encompassing standard microbiological culture, biochemical profiling, molecular analysis (qPCR), and phylogenetic identification based on the 16 S rRNA gene. This integrated approach confirmed the species identity and delineated the isolate's molecular genetic features. Crucially, whole-genome sequencing revealed a repertoire of virulence factors potentially central to the pathogenesis of streptococcal infections in animals. A finding of particular interest was the identification of the mf2 virulence gene, previously associated with prophages in Streptococcus pyogenes, which expands our understanding of the genetic mobility and evolutionary adaptability of SEZ. These results highlight the necessity of comprehensive diagnostic strategies for the identification and surveillance of pathogenic SEZ strains. The study provides new insights into the role of these bacteria as pathogens at the human-animal interface and emphasizes the need for further investigation into their molecular determinants of pathogenicity.