Phenotypic, Biochemical and Molecular Characterization of Streptococcus equi Isolates in Northern India

Streptococcus equi subsp. equi (S. equi) poses a significant threat to equine health globally. The bacteria causes strangles, a respiratory disease characterized by enlarged, abscessed lymph nodes, leading to airway obstruction. The bacterium, a Gram-positive, chain-forming, Lancefield group C β-hemolytic Streptococcus, is closely related to S. equi subsp. zooepidemicus and distinction between these species is challenging. The present study focused on characterization of S. equi isolates from horses in northern India, aiming at elucidation of their sugar fermentation patterns. Nasal and nasopharyngeal swabs collected from different geographical regions of northern India, yielding S. equi isolates were characterized phenotypically, biochemically and at molecular level. Phenotypic identification revealed typical characteristics of S. equi, including beta-hemolysis on blood agar and majority of them depicted typical mucoid colony characteristic. Biochemical characterization confirmed the identity of the isolates, with most exhibiting fermentation of maltose, lactose, sorbitol and trehalose. PCR analysis targeting the SeM gene provided additional confirmation, displaying a 541 bp product, indicative of S. equi. The study underscores the prevalence of S. equi in equines in India and emphasizes the importance of accurate diagnosis for timely intervention and disease management. The findings contribute to the understanding of S. equi epidemiology and aid in the development of effective control measures to mitigate the impact of strangles outbreaks in the region.

The online version contains supplementary material available at 10.1007/s12088-024-01420-5.