| Avian Salmonellosis is one of the main bacterial infectious diseases that endanger the healthy development of poultry industry in China.Salmonella can not only spread horizontally,but also spread vertically through eggs,which can cause more infection.In production practice,Salmonellosis is often controlled by antibiotics,due to the irrational use of antibiotics,Salmonella resistance is becoming more and more widespread.In order to understand the prevalence and drug resistance of Salmonella gallinarum in Hebei Province,this study carried out isolation in this area,as well as detection of virulence genes and drug resistance.The findings are as follows:1.Isolation and identification of Salmonella gallinarum in Hebei ProvinceIn this study,collected 588 anal swab samples from 16 chicken farms in Hebei,including Qinhuangdao,Tangshan,and Zhangjiakou in 2019~2020,using routine bacterial isolation and identification,staining microscopy,biochemical identification and PCR methods to detect Salmonella infection.The results showed that 150 strains of Salmonella were isolated,and the positive rate of farm was 50%,the average positive rate of individuals was 25.51%;The serotypes of isolates were identified by glass plate agglutination test,the results revealed that S.Gallinnnarum-Pullorum detection rate was 61.33%(92/150),S.Enteritidis detection rate was24.00%(36/150),S.Paratyphi A detection rate was 11.33%(17/150),S.Paratyphi B detection rate was 1.33%(2/150)and S.Aberdeen detection rate was 0.67%(1/150),S.Gallinnnarum-Pullorum and S.Enteritidis were the dominant serotypes.2.Detection of virulence gene and pathogenicity of Salmonella gallinarum isolates in Hebei Province27 virulence genes were detected by PCR method,and its result was that 25 virulence genes were detected,and the total detection rate was 92.59%.Among them,spv A,sii E,spv B,spv R,inv H,sse L,mgt C,spv D,spi4 H virulence genes was between 97.33~100%;The detection rate of sop E,sip C,sef A,sif A,orf319,mis L,pip C virulence genes was between 90.00%~95.33%;The detection rate of spv C,hil A,pef A,sip A,stn P1,rck virulence genes was between 81.33%~89.33%;The detection rate of sop B,ssr A,ssa B virulence genes was between 61.33%~70.00%;ssa R and rmb A virulence genes were not detected.There were many virulence genes,among which the highest proportion of Salmonella gallinarum isolates containing 24 virulence genes was 34.67%(52/150).According to the isolation area,serotype results and virulence gene carrying status of Salmonella gallinarum,a total of 34 representative strains were screened for pathogenicity test.It was found that the test group had disease status,and the total lethality rate was as high as 81.18%,and in different regions and serotypes.3.Detection of drug-resistant phenotypes and drug-resistant genes of Salmonella gallinarum isolates in Hebei ProvinceThe drug-resistant phenotype test found that 150 strains of Salmonella gallinarum were resistant to 21 kinds of antibiotics,and resistant to streptomycin,ampicillin,sulfisoxazole,penicillin,erythromycin and lincomycin antibiotics,the highest proportion were between87.33%~99.33%;Resistant strains to ciprofloxacin,tetracycline,doxycycline,gentamicin,kanamycin,compound trimethoprim and neomycin antibiotics accounted for 30.00%~38.67%;Resistant strains to florfenicol,polymyxin B,enrofloxacin,cephalexin and cefradine antibiotics accounted for 22.67%~29.33%;The proportion of resistant strains to spectinomycin,ceftriaxone and ofloxacin was the lowest,being 10.00%,9.33% and 2.00% respectively.150 strains of Salmonella have serious multi-drug resistance to 21 antibiotics,with the highest resistance to 20 antibiotics,of which 6 antibiotics have the highest proportion of resistance to 48.67%(73/150).The resistance spectrum was P +AM+STR+SF+EM+LIN was the most popular.The detection of drug resistance genes found that a total of 19 drug resistance genes were detected among the 23 drug resistance genes,and the total detection rate was 82.61%(19/23).Among them,the detection rate of aad A1,bla TEM resistance genes is more than 90%;The detection rate of sul2 resistance genes is more than 80%;The detection rate of cat A1,sul1,bla OXA,aac(6)-Ib,aac C4,aad A2,tet B resistance genes were between 38.67%~50.00%;The detection rate of qnr B,sul3,aad B,qnr S,tet A resistance genes were between 11.33%~24.00%;The detection rate of bla PSE,qnr A,aac C2,and flo R resistance genes were between 0.67 %~9.33%;bla SHV,bla CMY,tet G and cml A resistance genes were not detected.The carrying of multidrug resistance genes showed that the highest proportion of Salmonella gallinarum isolates containing 3 drug resistance genes was 21.33%(32/150),and up to 16 drug resistance genes were carried at the same time.And found that drug-resistant phenotype and drug-resistant genes were positively correlated.The coincidence rate of the drug-resistant phenotype and drug-resistant genes of ?-lactam antibiotics was higher,which was 99.32%. |
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