Detection and differentiation of wild-type and a vaccine strain of Streptococcus equi ssp. equi using pyrosequencing.

The research article discusses the use of pyrosequencing, a DNA sequencing technique, to differentiate between the wild strain and vaccine strain of Streptococcus equi, the bacterium that causes strangles in horses, in order to manage the disease better.

Introduction and Context

• The research focuses on Streptococcus equi subspecies equi (S. equi), a bacterium that causes strangles, a contagious equine disease. Although there is a modified live vaccine (MLV) available to combat the disease, the vaccine itself can sometimes lead to clinical signs of strangles.
• Due to the contagious nature of the disease, it is critical to determine whether a horse showing clinical signs of strangles is suffering from the disease due to the wild-type strain or because of the MLV. This information is crucial for implementing quarantine measures and restricting disease spread.

Research Approach

• The study utilized an assay based on pyrosequencing. In this context, an assay refers to a laboratory procedure that helps to determine the presence or amount of a particular component. Pyrosequencing is a method that determines the order of base pairs in a DNA molecule.
• The assay specifically targets a single nucleotide deletion upstream of the SzPSe gene. This deletion is a distinguishing feature between the wild strain and the vaccine strain of S. equi.
• Through this research, the scientists aim to demonstrate the effectiveness of the pyrosequencing assay in accurately distinguishing between the wild and vaccine strains of S. equi.

Results and Conclusion

• The researchers tested a total of 96 clinical samples and isolates using this pyrosequencing assay.
• The results indicate that the assay was successful in differentiating between wild-type S. equi and the vaccine strains. It was also effective at discriminating S. equi from other species of Streptococci.
• The data showed that the vaccine strain of S. equi was identified in 61.7% of strangles cases in those horses that had a history of MLV vaccination. These results demonstrate the assay’s potential utility in managing and controlling outbreaks of strangles in horses.