Novel seM-types of Streptococcus equi subsp. equi identified in isolates circulating in Argentina.

BACKGROUND: Strangles is a worldwide infectious disease caused by Streptococcus equi subsp. equi that affects the upper respiratory tract of horses. Streptococcus equi subsp. equi characterisation by seM-typing is internationally used for epidemiological studies and comparison of isolates. OBJECTIVES: To identify and to compare the seM-types of Argentinian isolates of Streptococcus equi subsp. equi. STUDY DESIGN: Investigation of bacterial isolates using molecular and phylogenetic approaches. METHODS: A total of 59 Argentinian isolates of Streptococcus equi subsp. equi obtained between 2007 and 2019 were studied by seM-typing. The sequence similarity of Argentinian seM-types and the other alleles available on the seM database was determined using BLAST and phylogenetic analysis was performed using the Neighbour-Joining algorithm. The amino acid sequences were predicted and compared with the predicted amino acid sequence of the reference strain 4047 using the MEGA 7 software and PROVEAN tool. RESULTS: Eight seM-types were found among the isolates. Only one of them (seM-61) has been previously reported and the other seven alleles (seM-129, seM-130, seM-131, seM-132, seM-133, seM-134 and seM-135) were novel seM sequences. High genetic similarity was observed among the Argentinian seM-types, with the exception of seM-130. No functional effects of amino acid differences were predicted. MAIN LIMITATIONS: The number of related and unrelated isolates per year. CONCLUSIONS: Seven novel seM-types and seM-61 that were previously reported in Brazil were circulating in Argentina which were identified as circulating in Argentinian horses between 2007 and 2019. The high genetic similarity among the Argentinian and Brazilian seM-types suggests that there is a geographical distribution of strain types. The geographical restriction of strains is likely to reflect the movement of horses between different equine disciplines and neighbouring countries.

Characterisation of SEQ0694 (PrsA/PrtM) of Streptococcus equi as a functional peptidyl-prolyl isomerase affecting multiple secreted protein substrates.

Peptidyl-prolyl isomerase (PPIase) lipoproteins have been shown to influence the virulence of a number of Gram-positive bacterial human and animal pathogens, most likely through facilitating the folding of cell envelope and secreted virulence factors. Here, we used a proteomic approach to demonstrate that the Streptococcus equi PPIase SEQ0694 alters the production of multiple secreted proteins, including at least two putative virulence factors (FNE and IdeE2). We demonstrate also that, despite some unusual sequence features, recombinant SEQ0694 and its central parvulin domain are functional PPIases. These data add to our knowledge of the mechanisms by which lipoprotein PPIases contribute to the virulence of streptococcal pathogens.