Isolation And Identification Of Fox-derived Escherichia Coli And Study On Immunogenicity Of Extracellular Products In Qinhuangdao

Escherichia coli(E.coli)has brought serious losses to the fox breeding industry,in addition to using antibiotics to treat E.coli disease,the vaccine is also an effective way to prevent and control E.coli disease.In this study,we isolated and identified the pathogenic E.coli from fox.CHL-147 strain was used as the test strain to extract and purify its extracellular products(ECP).The enzyme activity,pathogenicity,and immunogenicity of ECP were detected.To provide reference data for exploring new potential subunit vaccines of E.coli.In this experiment,47 strains of E.coli from fox were isolated and identified from 165 samples collected from fur animal farms by routine laboratory methods,and the detection rate was 28.5%,of which 36 strains were pathogenic.7 different serotypes were detected by the glass plate agglutination test.O1 and O78 were the dominant serotypes in this region.In this experiment,47 strains of E.coli of fox were identified from 165 samples collected from fur animal farms by conventional laboratory methods such as differential culture and biochemical identification,with a detection rate of 28.5%.Among them,36 strains were confirmed to be pathogenic by the mouse challenge test.Through the glass plate agglutination test,7 different serotypes were detected in 36strains of pathogenic E.coli.O1 and O78 were the dominant serotypes in this region.The ECP of E.coli CHL-147 strain was extracted and purified by the saturated ammonium sulfate precipitation method.The enzyme activity of ECP was detected by the plate diffusion method,the results showed that the ECP of E.coli CHL-147 had protease activity and hemolysin activity.The protein components of ECP were preliminarily identified by SDS-PAGE gel electrophoresis and SDS-PAGE showed that the ECP was mainly distributed at 180 k Da and 110 k Da.Mice were injected intraperitoneally to detect the pathogenicity of the ECP.The results showed that E.coli CHL-147 strain ECP had weak pathogenicity,but ECP were associated with CHL-147 strains from 1.01×10~7 CFU to 7.08×10~5 CFU when ECP was infected with CHL-147 strains.The results showed that the ECP of E.coli CHL-147 strain could stimulate the humoral immune system of mice and increase the antibody level of mice,but it can't stimulate the cellular immune system.The results showed that the immunized mice had good resistance to CHL-147 strain,protection rate is 60%.A total of 852 proteins were detected by LC-MSMS,which have a wide range of biological functions.It was involved in many signaling pathways such as antibiotic synthesis,amino acid synthesis and carbon metabolism.Conclusion:O1 and O78 serotypes were predominant in 36 strains of pathogenic E.coli of the fox.ECP of CHL-147 strain had hemolysin and protease activities,which could reduce the LD50 of CHL-147 strain;ECP contains 852 protein ingredients,immunized mice excitation mouse liquid immune systems,have good immunization effects.