Relationship between wzy genes and serotype of Streptococcus suis

Objective To study the relationship between serotype-specific wzy genes and serotype of Streptococcus suis and evaluate the feasibility of Whole-Genome Sequencing (WGS) -based serotyping strategy for the serotype-specific wzy genes.

Methods Amino acid database of 54 wzy genes (1–31, 33, 1/2, NCL1-20 and Chz) for serotyping was established. All 767S. suis isolates available with WGS data and conventional serotype information were subjected to WGS-based serotyping by using the database.

Results Among the 767 genomes, 1 of 54 wzy genes was detected in 765 genome sequences. The remaining 2 genomes carried a novel wzy gene, named as NCL21 in this study. WGS-based serotyping predicted serotype of 94.13% (722/767) genomes, consistent with conventional serotyping. Discrepancy of two methods was observed in 45 genomes. The cps sequences of these genomes were obviously different from those of the serotype reference strains indicated by conventional serotyping method.

Conclusion WGS-based serotyping strategy for the serotype-specific wzy genes of S. suis is superior to conventional serotyping method.