Multilocus Sequence Typing Analysis Of Chicken Escherichia Coli

Chicken colibacillosis is caused by avian pathogenic colibacillosis.The clinical manifestations are septicemia,gasbag inflammation,peritonitis,perihepatic inflammation,pericarditis,ophthalmitis,arthritis,etc.The incidence rate is 11%-69%,and the mortality rate is 3.8%-72.9%,which brings huge losses to the poultry industry.There are many pathogenic strains of Escherichia coli,and the diseases of Escherichia coli are complicated.Therefore,the timely diagnosis of colibacillosis and the accurate typing of E.coli are of great significance for the control of chicken colibacillosis.From the visceral organs of the sick chicken and the air of the chicken coop,the morphology of the colony and the fungus were observed,the DNA of the isolates was extracted,the 16 S rDNA amplification was carried out,and the isolated strains were identified by sequencing ratio.At the same time,the pathological observation was carried out by observing the lesions of the diseased chickens and collecting the regular paraffin slices of the diseased materials.The results showed that the colony of the isolated strain on nutrient agar was round convex,smooth,moist,translucent and gray-white.The colonies on the eosin methylene blue agar plate showed metallic luster and round brown colonies.Brevibacterium with gram negative staining and bipolar staining.The homology with GeneBank Escherichia coli was 98.2%-99.3%.According to sequence analysis and bacterial colony morphology,sixty-five strains of Escherichia coli were identified,of which forty-two strains originated from clinic and tweenty-three strains from environment.The necropsy of sick chickens revealed hepatomegaly,cellulose exudation,cloudy air sac and yolk-like substance in abdominal cavity.Tissue observation showed that extrahepatic membrane was thickened and its surface was covered with fibrous pseudomembrane.Inflammatory cells increased around blood vessels and portal areas.The epicardium of myocardium was thickened,with a large amount of fibrous exudate on the surface,inflammatory cell infiltration,disordered arrangement of myocardial fibers and fracture of individual myocardial fibers.Through pathological changes and isolation and identification of Escherichia coli,chicken colibacillosis was diagnosed.Sixty-five strains of Escherichia coli were classified by multilocus sequencetyping,and virulence gene,serotype and drug sensitivity were analyzed to explore the relationship between genotype and pathogenic gene,serotype and drug resistance.The results showed that sixty-five strains of E.coli were divided into thirty-two sequence types(ST).Among them,there were thirteen known STs and nineteen new STs.The thirty-two STs belong to nine homologous complexes and two unique types in the database.It was divided into five groups and fourteen individual types by UPGMA.The air isolates of chicken houses were mainly ST-21,the anal swab isolates were mainly nST-8,the adult diseased chicken isolates were mainly ST-88,and the diseased chick isolates were mainly nST-11.STs from different sources have different crossovers except for individual strains,indicating that the main STs of different isolates are different.The types and dominant sequece types of E.coli are related to their parasitic environment and host age.There are nine strains of Escherichia coli and fourteen strains of ST,including three serotypes and seven STs in the chicken house air isolates;six serotypes and eight STs in adult chicken isolates.The serotype of the adult diseased chicken isolates contain the serotype of the chicken house air isolates,but the genotypes are individually crossed.It can be seen from the results that the ST resolution is higher and finer.Drug resistance of twenty-three strains(fourteen kinds of ST)of Escherichia coli to six kinds of twelve kinds of antibiotics was analyzed.The results showed that the isolates had the highest resistance rate to lincosamides(LINs),up to 100%,?-lactams(BLs)were 95.65%,tetracyclines(TCs)were 91.30%,aminoglycosides(AGs)and macrolides(MALs)were 86.96%,quinolones(QLs)were 82.61%.18 resistant spectrums were formed.E.coli is resistant to a variety of drugs.The detection rates of glgP,menA,fimC and fimH genes of sixty-five strains of Escherichia coli were 100%,the detection rate of evgA was 95.40%,and the detection rate of traB was 33.8%.Sixty-five isolates were formed with three virulence profiles,mainly glgP-menA-evgA-fimC-fimH virulence.