Genomic comparisons of Streptococcus suis serotype 9 strains recovered from diseased pigs in Spain and Canada

Abstract

Streptococcus suis is one of the most important bacterial pathogens in the porcine industry and also a zoonotic agent. Serotype 9 is becoming one of the most prevalent serotypes within the S. suis population in certain European countries. In the present study, serotype 9 strains isolated from a country where infection due to this serotype is endemic (Spain), were compared to those recovered from Canada, where this serotype is rarely isolated from diseased pigs. For comparison purposes, strains from Brazil and the only strain isolated from a human case, in Thailand, were also incorporated. Firstly, sequence types (STs) were obtained followed by detection of putative virulence factors. Phylogenetic trees were constructed using the non-recombinant single nucleotide polymorphisms from core genomes of tested strains. Most Spanish strains were either ST123 or ST125, whereas Canadian strains were highly heterogeneous. However, the distribution of putative virulence factors was similar in both groups of strains. The fact that ST16 strains harbored more putative virulence genes and shared greater similarity with the genome of human serotype 2 strains suggests that they present a higher zoonotic and virulence potential than those from Canada and Spain. More than 80% of the strains included in this study carried genes associated with resistance to tetracycline, lincosamides and macrolides. Serotype 9 strains may be nearly 400 years old and have evolved in parallel into 2 lineages. The rapid population expansion of dominant lineage 1 occurred within the last 40 years probably due to the rapid development of the porcine industry.Electronic supplementary materialThe online version of this article (10.1186/s13567-017-0498-2) contains supplementary material, which is available to authorized users.

A Case-Control Study to Investigate the Serotypes of S. suis Isolates by Multiplex PCR in Nursery Pigs in Ontario, Canada

“…Serotype 3 appeared in both case and control animals but was not found as frequently as the other serotypes. Interestingly, serotype 9, which, in previous studies has rarely been isolated from diseased pigs in Canada, appeared as frequently as serotype (2, 1/2) and its emergence has been shown in recent years [10].…”

Tools for Molecular Epidemiology of Streptococcus suis

“…WGS approaches have increasingly been used to investigate S. suis isolates, including molecular determination of serotype [44], characterization of outbreaks [45,46], evaluation of S. suis reinfection [47], and to determine the population structure of S. suis isolates of serotype 2 belonging to ST25 and ST28 [48,49], as well as of serotype 9 [50]. WGS-based bacterial typing strategies commonly use one of two approaches: SNP (sequence)-based, or MLST (allele)-based.…”

Chromosomal Conjugative and Mobilizable Elements in Streptococcus suis: Major Actors in the Spreading of Antimicrobial Resistance and Bacteriocin Synthesis Genes

“…After cleavage at a site called oriT, DNA is addressed to a type IV secretion system by a relaxase, thanks to its interactions with a coupling protein [18]. The main families of ICEs carrying antimicrobial resistance (AMR) genes described in S. suis are Tn916, Tn5252, and Tn1549 families [11][12][13][14][15]19,20]. Mosaic or composite elements resulting from tandem accretions of ICEs or internal insertions of ICEs within another ICE were reported [11][12][13][14][15]19,20].…”