Abstract:[Background] As an opportunistic pathogen, Trueperella pyogenes is frequently associated with mixed infections with porcine reproductive and respiratory syndrome virus, porcine circovirus, or Pasteurella, which can cause various non-specific suppurative infections. Some clinical symptoms are similar to those of Haemophilus parasuis infection. In this study, a bacterial pathogen showing β-hemolysis was isolated from the lung of an infected pig that died of respiratory symptoms in Jiangxi Province. [Objective] To investigate the species, biological characteristics, and genomic characteristics of the isolated pathogen. Our study aimed for better understanding of the pathogenesis of bacterial infection. [Methods] The morphology of the isolated bacteria was characterized by transmission electron microscopy and scanning electron microscopy. The pathogenicity, biological characteristics, and genomic characteristics of the bacteria were confirmed through animal experiments, drug sensitivity test, whole genome sequencing and bioinformatics analysis, respectively. [Results] Through morphology observation, identification of 16S rRNA gene, and phylogenetic analysis, it was confirmed that the isolated pathogen was Trueperella pyogenes and named JX18. Results of the drug sensitivity test showed that JX18 was resistant to clindamycin and lincomycin, but sensitive to other selected drugs. The results of animal experiments showed that typical symptoms of suppurative infection appeared in the abdomen of mice after the challenge of T. pyogenes JX18. All mice challenged with the highest dose died. Results of the whole-genome sequencing showed that JX18 carries important virulence genes, including plo, nanH, nanP, fimA, fimC and fimE. Moreover, these virulence genes have high homology with that of other T. pyogenes strains. Results suggested that genes involved in the carbohydrate transport and metabolism have the highest proportion in the genome of JX18. According to the VFDB and UniProtKB/Swiss-Prot databases, JX18 carries multiple histidine-kinase genes, response regulator genes, genes of the bicomponent regulatory system, and virulence genes related to adhesion, invasion, and secretion. [Conclusion] In this study, a high pathogenic pathogen, T. pyogenes JX18, was isolated in Jiangxi province and had been identified. Our study may enrich the pathogenic information of T. pyogenes, and provide the foundation for exploring strategies for the prevention and control of T. pyogenes infection.
