In vitro and in vivo expression of virulence genes in Trueperella pyogenes based on a mouse model

Trueperella pyogenes is an important opportunistic pathogen causing a number of pyogenic infections in ruminants and other animals. This microorganism expresses several extracellular virulence proteins that contribute to its pathogenic potential. To investigate the expression levels of haemolytic exotoxin pyolysin, neuraminidases, collagen-binding protein and fimbriae of T. pyogenes in routine culture and infection process, 10 T. pyogenes isolates which simultaneously harbored ftsY, plo, cbpA, fimA, fimC, nanP, and nanH genes were injected into 10/group Kunming (KM) mice to determine their virulence. In vitro expressions of these genes were determined by quantitative PCR. Subsequently, three typical isolates including an avirulent, a moderately virulent and a strongly virulent isolate were respectively injected into mouse model to determine the in vivo expression of these genes. Finally, significant correlation was observed between collagen-binding protein, neuraminidases, and fimbriae. The expression level of pyolysin was negatively correlated with the survival of injected mice. The time course of virulence gene expression was monitored based on the expression of virulence genes in mouse model. In conclusion, the in vitro and in vivo gene expression study showed a clear difference in virulence gene expression between virulent and non-virulent isolates.