Pan-genome analysis ofStreptococcus suisserotype 2 revealed genomic diversity among strains of different virulence

Streptococcus suis(SS) is an emerging zoonotic pathogen that causes severe infections in swine and humans. Among the 33 known serotypes, serotype 2 is most frequently associated with infections in pigs and humans. To better understand the virulence characterization ofS. suisserotype 2 (SS2) and discriminate the difference between virulent and avirulent strains in SS2, characterization of the genomic features of strains with different virulence is required. The result showed thatStreptococcus suishave an open pan-genome. The pan-genome shared by the 19S. suisserotype 2 strains was composed of 1,239 core genes and 2,436 accessory genes. COG analysis indicated that core genes are involved in the basic physiological function, but accessory genes related to tachytely evolution. Comparative analysis between core genomes of virulent strains and 9 avirulent strains suggested that srtBCD pilus cluster was a significant discrepancy between virulent and avirulent strains. Analysis between high virulent and group B low virulent strains showed 53 and 58 genes specific to each other. Moreover, genomes of avirulent strains tend to be larger than virulent strains; avirulent strains tend to possess more prophages sequences than virulent strains. Our findings could be contributed to a better understanding of the genomics ofS. suisserotype 2.

Automated summary

Streptococcus suis is an emerging zoonotic pathogen that causes severe infections in swine and humans, with serotype 2 being most frequently associated with infections. Understanding the genomic features of different virulent strains is important, with core genes involved in basic physiological functions and accessory genes related to evolution. Comparative analysis revealed significant differences in pilus clusters between virulent and avirulent strains, with avirulent strains having larger genomes and more prophage sequences.