To understand the pathogenicity,virulence genes,drug resistance genes,and drug resistance of Staphylococcus aureus isolated from yaks in some areas of Lhasa and Nagqu City,55 yak nasal swab samples were analyzed for S.aureus in this study.The cocci were isolated and identified,and the carriage of virulence genes and drug resistance genes,as well as the pathogenicity and drug sensitivity of the isolated S.aureus strains,were detected with PCR,artificially infected mice,and the K-B drug susceptibility disk method.Seven strains of S.aureus were isolated from the 55 yak nasal swab samples,with an iso-lation rate of 12.73％.The isolated strains were all pathogenic to mice,with a fatality rate exceeding 60％.These seven strains of S.aureus carried three drug resistance genes(tetM,tet,and mecA)and six virulence genes(seb,sec,clfA,hla,hlb,and nuc).The detection rate of the three drug resistance genes was 100％,whereas the detection rate of the six virulence genes in the isolates ranged from 83.33％to 100％.The resistance rates of the isolated strains to penicillin,ampicillin,and cotrimox-azole reached 85.71％-100％,whereas the resistance rates to tetracycline and ceftazidime were both 28.57％.Thus,yaks in Lhasa and Nagqu cities were found to be infected by S.aureus strains carrying various drug-resistance genes and virulence genes.These strains were highly pathogenic and showed sensi-tivity to most antibacterial drugs.These findings may serve as a reference for treating S.aureus infection in yaks in the cities of Lhasa and Nagqu.