Novel Capsular Polysaccharide Loci and New Diagnostic Tools for High-Throughput Capsular Gene Typing in Streptococcus suis.

Abstract

Streptococcus suis is an important pathogen of pigs and may cause serious disease in humans. Serotyping is an important tool for detection and epidemiological studies of S. suis Thirty-three reference serotypes and nine novel cps loci (NCLs) are recognized in S. suis To gain a better understanding of the prevalence and genetic characteristics of NCLs, we investigated the serotype identity of 486 isolates isolated between 2013 and 2015 in China by capsular gene typing methods. Two hundred seventy-six isolates carried NCLs belonging to 16 groups, 8 of which appear to have not been reported previously. These isolates showed autoagglutination, polyagglutination, or nonagglutination with reference antisera and thus were nonserotypeable. Almost all isolates carrying the unknown NCLs were encapsulated, with various capsular thicknesses, indicating that they are most likely novel serotypes. To simultaneously identify the currently recognized 17 NCLs, an 18-plex detection system using the Luminex xTAG universal array technology was developed. Our data also provide valuable genetic information for monitoring the variations within NCLs by investigating the genetic characteristics of different subtypes within NCLs.