Trueperella pyogenes(TP),an important livestock and poultry pathogen,can cause vari-ous diseases such as suppurative pneumonia,arthritis,and mastitis in animals.The newly brought calves of one cattle farm occurred respiratory diseases and accompanied death in Yunyang,Chongqing,based on post-mortem examination,suppuration nodules were found in the lungs,and microscopic observation of tissue smears with staining showed that a lot of short rod shape bacteri-a were in tissue.The bacteria were isolated and purified from the clinic lung tissue and analyzed by 16S rRNA sequence,the result showed the infectious bacteria was Rueperella pyogenes,and it was nominated as TpCQ-yy1.TpCQ-yy1 cultured on rabbit blood agar plates could form double-zone hemolysis,and can utilize glucose and lysine.Interestingly,the drug-resistance characteristics of TpCQ-yy1 partially changed along with the variation of the culture medium.Pathogenicity analysis showed that TpCQ-yy1 could make suppurative lesions in the lungs of mice infected via the thorac-ic and intraperitioneal route,and later led mice to death,while the subcutaneous and intramuscular routes of infection had only suppurative foci at the site of injection and were dose-dependent and non-lethal.The genome size of TpCQ-yy1 is 2.335 Mb,which encoding 2 107 proteins,and the phy-logenetic analysis showed TpCQ-yy1 is close to Trueperella pyogenes TP1 strain but away from other strains.TpCQ-yy1 infection could promote the secretion of inflammatory factors of macro-phage.TpCQ-yy1 inactivated bacterial vaccine and recombinant hemolysin(rPLO)subunit vaccine could induce high levels of antibodies production in mice immunized via subcutaneous and muscle route,but only provided 33.3％-66.7％protection to the immunized mice against TpCQ-yyl infec-tion via intraperitioneal route.This research provides a fundamental basis for the understanding of the biological characteristics,pathogenicity,and prevention and control of Trueperella pyogenes.