This study aims to understand the epidemic distribution characteristics,antimicrobial resistance,virulence genes,and biofilm adhesion ability of Enterococcus in yaks on the Tibetan plateau.Three hundred and forty-six fresh yak fecal samples and 311 milk samples were collected from four provinces on the Tibetan plateau(Xizang,Sichuan,Gansu,Qinghai),totaling 657 sam-ples.Bacterial isolation and identification were conducted,followed by 16S rDNA gene detection and the construction of a systematic evolutionary tree.The isolated strains were tested for antimi-crobial resistance and virulence genes using PCR,and sensitivity tests were performed using 18 types of antibiotics.The biofilm adhesion ability of the isolated bacteria was determined using an improved semi-quantitative crystal violet staining method.The results showed that the total isola-tion rate of Enterococcus was 32.27％,with Sichuan having the highest at 60.23％,followed by Gansu,Qinghai,and Tibet autonomous region at 42.70％,23.47％,and 18.31％respectively.In terms of sample types,the isolation rate in fecal samples was 36.71％,and in milk samples,it was 27.33％.Through PCR amplification,bands of approximately 1 400 bp were obtained,and 5 strains were selected for evolutionary analysis,forming a separate cluster.Among the 212 isolated strains,a high resistance to clindamycin,quinupristin-dalfopristin,linezolid,levofloxacin,and erythromycin was observed,with various resistance phenomena,accounting for 60.85％.Only 5 out of 12 resist-ant genes were detected,namely erm(B),tet(L),tet(O),tet(M),and ant(6)-Ia.All 13 virulence genes were detected in Enterococcus,with detection rates in the range of 5.19％to 95.76％,where cpd was 95.75％,gelE was 91.98％,efaA was 86.79％,asal was 86.32％,and the rest ranged from 5.19％to 55.66％.The fsr virulence gene was not detected in Enterococcus from milk sources.Among the isolated strains,3.30％showed medium adhesive ability,48.58％showed weak adhesive ability,and 48.11％showed no adhesive ability.The above research revealed the preva-lence of yak derived Enterococcus,the carrying status of resistance and virulence genes,and the correlation between biofilm phenotypes,laying the foundation for mastering research data on yak-derived Enterococcus in the Tibetan plateau.

This study aims to understand the epidemic distribution characteristics,antimicrobial resistance,virulence genes,and biofilm adhesion ability of Enterococcus in yaks on the Tibetan plateau.Three hundred and forty-six fresh yak fecal samples and 311 milk samples were collected from four provinces on the Tibetan plateau(Xizang,Sichuan,Gansu,Qinghai),totaling 657 sam-ples.Bacterial isolation and identification were conducted,followed by 16S rDNA gene detection and the construction of a systematic evolutionary tree.The isolated strains were tested for antimi-crobial resistance and virulence genes using PCR,and sensitivity tests were performed using 18 types of antibiotics.The biofilm adhesion ability of the isolated bacteria was determined using an improved semi-quantitative crystal violet staining method.The results showed that the total isola-tion rate of Enterococcus was 32.27％,with Sichuan having the highest at 60.23％,followed by Gansu,Qinghai,and Tibet autonomous region at 42.70％,23.47％,and 18.31％respectively.In terms of sample types,the isolation rate in fecal samples was 36.71％,and in milk samples,it was 27.33％.Through PCR amplification,bands of approximately 1 400 bp were obtained,and 5 strains were selected for evolutionary analysis,forming a separate cluster.Among the 212 isolated strains,a high resistance to clindamycin,quinupristin-dalfopristin,linezolid,levofloxacin,and erythromycin was observed,with various resistance phenomena,accounting for 60.85％.Only 5 out of 12 resist-ant genes were detected,namely erm(B),tet(L),tet(O),tet(M),and ant(6)-Ia.All 13 virulence genes were detected in Enterococcus,with detection rates in the range of 5.19％to 95.76％,where cpd was 95.75％,gelE was 91.98％,efaA was 86.79％,asal was 86.32％,and the rest ranged from 5.19％to 55.66％.The fsr virulence gene was not detected in Enterococcus from milk sources.Among the isolated strains,3.30％showed medium adhesive ability,48.58％showed weak adhesive ability,and 48.11％showed no adhesive ability.The above research revealed the preva-lence of yak derived Enterococcus,the carrying status of resistance and virulence genes,and the correlation between biofilm phenotypes,laying the foundation for mastering research data on yak-derived Enterococcus in the Tibetan plateau.