Molecular study of Streptococcus equi isolated from horses with strangles in Iraq.

This research focuses on studying the genetic makeup of a particular strain of the bacteria Streptococcus equi, responsible for strangles, a severe respiratory disease in horses, specifically in Iraq. The purpose is to understand its genetic diversity, relationships to other strains, and spread.

Study Purpose and Methodology

• The goal of this study was to explore the molecular characteristics of Streptococcus equi, the agent causing strangles in horses, specifically in Iraq. It was the first of such studies in the country to work towards identifying a specific gene, labelled as seM, as well as to conduct a comparative analysis of the strain’s phylogeny (evolutionary history).
• The study used 59 S. equi isolates previously obtained from the clinical samples of horses. The conventional Polymerase Chain Reaction (PCR) method, which aids in DNA amplification for further study, was applied to identify the presence of S. equi, specifically targeting the seM gene.
• Out of these 59 isolates, nine PCR-positive isolates were selected for additional study involving sequencing and allele typing of the seM gene.

Results and Findings

• Out of the initial 59 isolates, the researchers confirmed 49 as S. equi based on the molecular assay. In other words, these contained the signature seM gene of the strangles-causing bacteria.
• The nine selected PCR products underwent further sequencing and allele typing. During this process, the researchers identified the seM-97 allele in S. equi for the first time in Iraq.
• Upon conducting a phylogenetic analysis, the researchers found a close relationship between the Iraqi strains of S. equi and a strain from Iran, displaying 100% genetic sequence identity. This finding suggests an important epidemiological connection indicating possible regional spread of the bacterial strain from Iran.

Conclusion

• The research marks the first investigation into allele typing in Iraq, specifically identifying the seM-97 allele of S. equi. It brings attention to the unique amino acid variations characterizing this allele.
• The study’s findings signify genetic similarities observed between the S. equi strains in Iraq and a particular strain from Iran. This implies potential regional dissemination of this infectious agent causing strangles in horses, which might indicate a common source or similar disease management practices in this region.