Comparative Genome Analysis of Two Serotype 8 Strains Identifies Two New Virulence-Associated Genes.

is an important zoonotic pathogen that can cause meningitis and septicemia in swine and humans. Among numerous pathogenic serotypes, serotype 8 has distinctive characteristics such as a high detection rate and causing multi-host infection. There is no complete genome of serotype 8 strains so far. In this study, the complete genome of two serotype 8 strains, virulent strain 2018WUSS151 and non-virulent strain WUSS030, were sequenced. Comparative genomic analysis showed that the homology of the two genomes reaches 99.68%, and the main difference is the distinctive prophages. There are 83 genes unique to virulent strain 2018WUSS151, including three putative virulence-associated genes (PVGs). Two PVGs, and are passenger genes in ISSsu2 family transposons that are able to form circular DNA intermediates during transposition, indicating the possibility of horizontal transmission among strains. The deletion mutant of PVGs or attenuated the virulence of serotype 2 virulent SC070731 in a mouse infection model, confirming their role in virulence. These findings contribute to clarifying the genomic characterization of serotype 8 and pathogenesis.