Analysis Of Drug Senstivity And Genetic Correlation For Swine Extraintestinal Pathogenic Escherichia Coli

Escherichia coli is an important zoonotic pathogen.Piglets edema disease,yellow or white scour of newborn piglets are typical diseases caused by E.coli.They trouble the veterinary clinic for long.New symptoms such as Pneumonia,nephritis, meningitis and septicemia caused by E.coli are increasing with the development of swine industry.And these extraintestinal infections are also similar to human.The specialized strains of E.coli that cause most extraintestinal diseases were classified as extraintestinal pathogenic E.coIi(ExPEC),which shows higher morbidity,mortality and no typical serotypes.Now antimicrobial therapy is the only available tool for treating clinical infections of ExPEC because of no vaccine.The resistance of ExPEC emerged due to the wrong use of the antibiotics and the feedstuff additive at the clinic. Extended-spectrumβ-lactamase(ESBL)-producing strains and the dissemination of resistant vectors are of increasing concern of the failure of antibiotic therapy and public health.It's helpful for clinical treatment to detect the resistance of ExPEC to common antibiotics and the possibility of resistance transmission,based on the detecting of serotype,virulence factors and animal experiments of ExPEC.so we carried out the following work to analyse the drug senstivity and molecular characteristics for swine ExPEC:1.We researched the drug minimum inhibitory concentration of 315 swine ExPEC isolates from the clinic.These isolates of Expec showed multiple drug resisitance, and only sensitived to cephalosporins.95.2%were resistant to at least five antimicrobials and 60.6%resistant to more than 10.the most popular multiresistant patterns was AMP+STR+KAN+NEO+GEN+CIP+OFX+TE+TMP+SDM.2.We established the PCR methods for detection of 27 resistance genes includingβ-lactams,aminoglycosides,tetracyclines,quinolones,trimethoprim and sulfonamides,then appliesed them to the ExPEC.For each antimicrobial agent, ampicillin resistance was primarily mediated by bla_TEM,aminoglycosides by aac(3)-Ⅳ, strAstrB and aphA1,quinolones resistance by mutations in gyrA,tetracycline resistance by tet(B) and tet(G),trimethoprim resistance by dfrA7,dfrA12,dfrA13,and sulfadimidine resistance by sul1 and sul2.Strains which harbored several genes that conferred resistance to the same antimicrobial agent were often significantly more multiresistant than others.3.We detected the intⅠgene to identify integron,and amplified variable region to determine gene cassettes.86(27.3%) ExPEC isolates were integron positive,which harbored dfrA14,aadA2,aadA22,aadA5,dfrA17,dfrA17-aadA2,dfrA1-aadA1, dfrA12-aadA2,dfrA17-aadA5 gene cassettes in five major different variable regions.4.We identified ESBL isolates and classified their genotypes.Two isolates with bla_TEM-I+bla_CTX-M-I4-genotype ESBL were selected.They were both resistant to more than 10 drugs.5.We reseached genetic correlation for 38 swine ExPEC isolated from twelve pig farms of three provinces.Analysis of plasmid map proved that 1 to 2 different plasmids were popular in a farm,but distinguishing to the other farms.BOX-PCR demonstrated that the genetic correlation was higher in the same farm than in the others.Resistant phenotype and genotype in the same farm were not significantly (P＞0.05).These above paved a way to certify that strains,plasmids and antibiotic resistance are regional and transmissible in the pig farm.