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Updated: Feb 27, 2026

Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR RS-PCR
Published on: November 4, 2016
A single amino acid polymorphism in the glycosyltransferase CpsK defines four Streptococcus suis serotypes
David Roy1, Taryn B T Athey2, Jean-Philippe Auger1
1Swine and Poultry Infectious Diseases Research Centre, Faculty of Veterinary Medicine, University of Montreal, Saint-Hyacinthe, QC, J2S 2M2, Canada.
Abstract:
The capsular polysaccharide (CPS) is the major virulence factor of the emerging zoonotic pathogen Streptococcus suis. CPS differences are also the basis for serological differentiation of the species into 29 serotypes. Serotypes 2 and 1/2, which possess identical gene content in their cps loci, express CPSs that differ only by substitution of galactose (Gal) by N-acetylgalactosamine (GalNAc) in the CPS side chain. The same sugar substitution differentiates the CPS of serotypes 14 and 1, whose cps loci are also identical in gene content. Here, using mutagenesis, CPS structural analysis, and protein structure modeling, we report that a single amino acid polymorphism in the glycosyltransferase CpsK defines the enzyme substrate predilection for Gal or GalNAc and therefore determines CPS composition, structure, and strain serotype. We also show that the different CPS structures have similar antiphagocytic properties and that serotype switching has limited impact on the virulence of S. suis.
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