Abstract
Strangles is among the most widespread infectious bacterial diseases of horses, caused by the Gram-positive microorganism Streptococcus equi. The aim of this study was to isolate Strangles is among the most widespread infectious bacterial diseases of horses, caused by the Gram-positive microorganism Streptococcus equi. circulating in horse populations in Kazakhstan and to perform molecular genetic characterization of the obtained isolate. During the monitoring studies, biological samples were collected from horses with clinical signs of streptococcal infection in eight regions of the Republic of Kazakhstan. The samples included nasal swabs, purulent exudates from submandibular lymph nodes, and blood sera. Following bacteriological isolation of the pathogen, species identification was confirmed by real-time polymerase chain reaction (PCR). Genomic DNA was extracted from a single confirmed isolate and subsequently subjected to whole-genome sequencing and bioinformatic analysis. PCR analysis confirmed the presence of S. equi-specific genetic material in the examined samples. Whole-genome sequencing enabled assembly of a draft genome with a total length of 2,253,416 base pairs, containing approximately 1,500 predicted genes, including multiple prophage regions and transfer RNA (tRNA) sequences. Phylogenetic analysis based on the M-protein (seM) gene demonstrated close genetic relatedness of the studied isolate to strains previously reported from Russia and China. Comparative genomic analysis also revealed genetic similarity between Strangles is among the most widespread infectious bacterial diseases of horses, caused by the Gram-positive microorganism Streptococcus equi and related streptococcal species, including Streptococcus dysgalactiae and Streptococcus canis. The obtained results expand current knowledge on the molecular genetic features of S. equi circulating in Kazakhstan and provide a scientific basis for molecular surveillance, epidemiological tracking, and further improvement of diagnostic and preventive strategies for strangles.