Distribution and characterization of Streptococcus suis serotypes isolated from January 2015 to June 2020 from diseased pigs in Québec, Canada.

Streptococcus suis is one of the most important swine bacterial pathogens causing economic losses. This report presents the serotype distribution of S. suis recovered from diseased pigs in Québec from January 2015 to June 2020. Serotypes 1/2 and 2 predominated, followed by serotypes 7, 3, 5, 4, 9, 1, and 14. Compared to previously reported data, very few changes could be observed concerning the serotype distribution, indicating a relative stability. Half of the untypable isolates did not belong to the species S. suis sensu stricto, as determined by recN polymerase chain reaction. Less than 10% of "real S. suis" isolates were untypable. The genetic diversity of S. suis serotypes 1, 2, and 14, as analyzed by multilocus sequence typing, was mainly represented by sequence type (ST)1, ST28, ST25, and ST94. All ST1 isolates (considered highly virulent) belonged to either serotype 1 or 14.

Streptococcus suis est l'un des agents pathogènes bactériens porcins les plus importants et qui cause d'importantes pertes économiques. Ce rapport présente la distribution des sérotypes isolés à partir de porcs malades au Québec de janvier 2015 à juin 2020. Les sérotypes 1/2 et 2 prédominent, suivis des sérotypes 7, 3, 5, 4, 9, 1, et 14. Peu de changements par rapport aux années précédentes ont pu être observés en ce qui concerne la distribution des sérotypes. Plus de la moitié des isolats n'appartenaient pas à l'espèce S. suis sensu stricto, selon la réaction en chaîne par polymérase recN. Moins de 10 % des isolats des « vrais ¼ S. suis étaient non-typables. La diversité génétique des sérotypes 1, 2, et 14 de S. suis, telle qu'analysée par typage de séquences multilocus, était principalement représentée par les types de séquence (ST)1, ST28, ST25 et ST94. Tous les isolats ST1 (considérés comme hautement virulents) appartenaient aux sérotypes 1 ou 14.(Traduit par les auteurs).

Application of phage display technology for the production of antibodies against Streptococcus suis serotype 2.

Streptococcus suis (S. suis) serotype 2 infection is a problem in the swine industry and responsible for most cases of human infection worldwide. Since current multiplex PCR cannot differentiate between serotypes 2 and 1/2, then serotype-specific antibodies (Abs) are required for serotype identification to confirm infection by serotype 2. This study aimed to generate Abs specific to S. suis serotype 2 by phage display from a human heavy chain variable domain (VH) antibody library. For biopanning, whole cells of S. suis serotype 2 were used as the target antigen. With increasing selection stringency, we could select the VH Abs that specifically bound to a S. suis serotype 2 surface antigen, which was identified as the capsular polysaccharide (CPS). From ELISA analysis, the specific phage clone 47B3 VH with the highest binding activity to S. suis serotype 2 was selected and shown to have no cross-reactivity with S. suis serotypes 1/2, 1, and 14 that shared a common epitope with serotype 2 and occasionally cause infections in human. Moreover, no cross-reactivity with other bacteria that can be found in septic blood specimens was also observed. Then, 47B3 VH was successfully expressed as soluble 47B3 VH in E. coli TG1. The soluble 47B3 VH crude extract was further tested for its binding ability in a dose-dependent ELISA assay. The results indicated that the activity of phage clone 47B3 was still retained even when the Ab occurred in the soluble form. A quellung reaction demonstrated that the soluble 47B3 VH Ab could show bioactivity by differentiation between S. suis serotypes 2 and 1/2. Thus, it will be beneficial to use this VH Ab in the diagnosis of disease or discrimination of S. suis serotypes Furthermore, the results described here could motivate the use of phage display VH platform to produce serotyping antibodies.