Diversity of seM in Streptococcus equi subsp. equi isolated from strangles outbreaks.

This research looks at variations in the M protein gene (seM) in a bacterium called Streptococcus equi that causes a major respiratory disease in horses in Brazil. They found a large diversity of seM alleles amongst the Brazilian horse population studied, many of which have not been previously identified.

Objective and Methods of the Study

• This study intends to analyze and differentiate S. equi bacterial isolates taken from equine clinical specimens in southern Brazil from 1994 to 2010 to comprehend the strains causing strangles, a prominent upper respiratory tract disease of horses.
• The variations in the M protein gene (seM) unique to S. equi were assessed in 47 isolates collected from outbreak situations on horse breeds including Thoroughbreds, Crioulos, and Brasileiro de Hipismo.
• The variation in the seM alleles was characterized by comparing the variable region sequences of the seM gene.
• The seM alleles were also examined based on their phylogenetic grouping by Neighbor-joining analysis to understand their geographical distribution within southern Brazil.

Findings of the Study

• Fifteen different alleles of the seM gene were identified among the 47 S. equi bacterial isolates analyzed.
• Of these 15 alleles, only one (seM-61), identified in seven isolates (14.9%), was already listed in the PubMLST-seM database, which maintains records of different seM alleles worldwide.
• The remaining 14 alleles were newly identified. Of these, allele seM-115 was the most prevalent, found in 13 isolates (27.7%), followed by allele seM-117 in 10 isolates (21.3%).

Significance of the Research

• Results reveal a higher diversity of M protein alleles in the Brazilian horse population’s S. equi isolates compared to globally documented data in PubMLST-seM.
• Among the 15 seM alleles identified, 14 allele sequences were newly discovered expansion to the existing knowledgebase.
• Identifying these alleles contributes to controlling the disease as it provides a guide for the selection of strain types for the production of commercial and autogenous vaccines.