Isolation And Identification Of Porcine Staphylococcus Aureus And Analysis Of Their Drug Resistance And Virulence Gene Distribution

Staphylococcus aureus(S.aureus)is a zoonotic pathogen with potential risk to both human and animals,especially with the inceasing of methicilln-resistant Staphylococcus aureus(MRSA),which causes great trouble in clinical treatment.To study the drug resistance,virulence factors,agr type strains and pathogenicity of Staphylococcus aureus is of great significance to public health and safety.(1)Isolation and identification:S.aureus was isolated from 300 samples collected from pig farms in Hunan Province.Biochemical characteristics were identified;NUC and 16 S r RNA genes were identified by PCR;5 of them were used as S.aureus evolution analysis.Results 65 strains of S.aureus were successfully isolated,the isolation rate was 21.67%.The isolation rate of sows was 19.71%(28 / 142)and piglets was 23.41%(37 / 158).NCBI comparative analysis of 16 S r RNA sequencing results:the similarity is 98.0% ? 100.0%.(2)Drug resistance analysis:15 kinds of common antibiotics were used for drug sensitivity test,cefoxitin method was used to identify MRSA,and 11 genes of 8 kinds of antibiotics were detected by PCR.Results: all the isolates were not resistant to vancomycin.CHL,GEN,PEN,EM,CLI,LEV,AMP,TET,NOR,CIP,SXT,FOX,OXA and CEF were100%,96.92%,95.38%,95.38%,84.61%,80%,72.3%,72.3%,69.23%,69.23%,63.07%,4.61%,6.15% and 6.15%,respectively.All isolates were resistant to at least 4 different antibiotics.Among the multi drug resistant strains,10 were the most resistant,followed by 9,11 and 7.The positive rates of gyr A,blaz,aac(6 ')/ aph(2'),tet K and tet M genes were all higher than 90%,while Van A was not detected,most of the isolates carried multiple drug resistance genes.(3)Agr typing,pathogenicity test and distribution of virulence factors:Detection of 11 virulence genes,agr typing and mouse test.Results: HLB and HLD genes were detected in all isolates;the detection rate of HLA and ICAA was more than 90%;the carrying rates of sea,SEB,ETA,ETB and fnba were 23.07%,40%,29.23% and 30.76%,respectively.The detection rate of TST gene was 4.61%.The detection rate of PVL gene was 1.53%.There are7 kinds of species carrying multiple virulence factors,which are 3,4,5,6,7,8 and 9,accounting for 3.07%,29.23%,24.51%,13.84%,7.69%,18.46% and 3.07% respectively.In the experiment of infecting mice,17 strains of isolated bacteria infected Kunming mice during the experiment,and the pathogenicity rate was 26.15%(17 / 65).Agr typing: 42 strains of 64.62%(42 / 65)S.aureus were classified and identified.Among them,the proportion of agr type ? was the highest,and 23 strains of S.aureus were not identified as agr type.The number of virulence factors of agr positive strains was significantly higher than that of negative strains.The drug resistance rate of Staphylococcus aureus isolated from lung is higher than that of swab,the number of virulence factors of coagulase positive bacteria is higher than that of negative bacteria,and the pathogenicity of coagulase positive bacteria is stronger than that of negative bacteria.