posted on 2022-09-06, 15:08authored byEmma Moloney
Streptococcus equi subsp. equi is the causative agent of strangles, a highly contagious upper respiratory infection of horses. A molecular typing scheme and database based on the variability of the S. equi SeM protein has been developed for use as an epidemiological tool to discriminate between S. equi strains. The majority of SeM alleles in the database are of UK origin. To date, there has been very little published material detailing the molecular
epidemiology of S. equi isolates in any country other than the UK. The population of S. equi
strains in Ireland had not been studied. This project was undertaken to identify and classify
Irish strains of Streptococcus equi ssp equi within the Irish Horse Industry throughout
Ireland. Using SLST (single locus sequence typing) based on the seM gene of Streptococcus
equi ssp equi, 230 strains were analysed. Of these isolates 171 samples gave an amplicon.
These amplicons were sequenced and the sequences analysed for similarities. A total of 163
samples gave robust sequence information. This analysis allowed division of the isolates into
20 groups, 12 of which contain at least 2 isolates and 8 groups containing single isolates. The
sequences were compared to the Streptococcus equi seM database in the UK. The findings
show that at least one of the groups is unique to Ireland, and some are most likely of UK
origin, but many more are probably passed back and forth between the two countries.
Analysis of the encoded protein sequences indicated that there were 17 positions where there
were amino acid changes between different groups. However, it is unlikely that these
changes alter the fibrinogen binding properties of the SeM protein