Molecular Epidemiological Survey Of Resistance And Virulence Genes Of Escherichia Coli From Dead Duck Embryos

Escherichia coli(E.coli)is an important foodborne pathogen,ithas extensive host nature,and it can cause zoonosis.It has become one of the serious damage to the breeding of pathogenic bacteria for development,especially E.coli can cause death in duck embryo hatching process,but also likely to cause a large area of infection and caused serious damage to the breeding.This paper studies the infection status of pathogenic bacteria in dead duck embryos to explore the causes of death of duck embryos during hatching.;Through the drug sensitivity test and drug resistance gene detection,the drug resistance and resistance genes of E.coli from duck embryo were mastered.The pathogenicity of E.coli derived from duck embryo was investigated by detecting the virulence genes of Escherichia coli and the type of ETT2 virulence island.This study is divided into five parts.1.Isolation and identification of bacteria in dead duck embryosThrough isolating,Staining microscopy and 16 SrDNA identification of bacteria in undamaged dead duck embryos.A total of 370 strains of bacteria belonging to 27 species were isolated from 415 duck embryos,and 324 duck embryos were infected by bacteria with78.1% infection rate.Among all the isolated bacteria,E.coli and Salmonella accounted for33.2% and 25.4%,which were the main bacteria in the dead duck embryos.The results showed that the infection of bacteria was the main reason for the increase of embryo mortality and weak hatchability,and E.coli was one of the main pathogens.2.Investigation of drug resistance of E.coli from duck embryosThe resistance of 18 kinds of antibiotics(aminoglycosides,quinolones,β-lactam drugs)to 123 E.coli strains from ducks was detected by the disk method(Kirby-Baure method)that recommended by WHO(WHO).The results showed that 123 E.coli strains showed different degrees of resistance to the 18 antibiotics: to beta lactam drugs,the resistance rates tocephalexin,ampicillin and cefalothin were 82.9%,77.2% and 72.4%,respectively;to quinolone,the resistance rates to ciprofloxacin,norfloxacin and levofloxacin were 54.5%,49.6% and 48%,respectively.To aminoglycoside drugs,the resistance rates to streptomycin,kanamycin and gentamicin were 39%,30.9% and 10.6%,respectively.the drug resistance in the rate of,The resistant rate to polymyxin B was 13.8%,which was the lowest one in the resistant rates to the 18 kinds of antibiotics.The study shows that the aminoglycosides and polymyxin B can be selectively used in the treatment and prevention of pathogenic bacterial infections in breeder ducks in Taian city.3.Detection and identification of resistance genes of E.coli from duck embryosBased on three PCR detection to 123 strains of E.coli carbepenems gene,the results showed that 123 strains of E.coli were amplified by ant(3 ")-Ia,AAC(6")-Ib,APH(3’)three specific bands of-IIa,resistance gene carrying rate were 22.8%,3.3%,2.4%.The 16 S methylation gene was amplified by PCR.The results showed that 123 E.coli strains amplify the three heavy specific bands of armA,rmtA and rmt B,and the carrier rate of drug resistance was 95.1%,19.5% and 0.8% respectively.The results of PCR amplification of quinolone resistant strain showed that the carrying rate of qnrD was 11.4%,the carrying rate of qnrS was22.0%,the carrying rate of oqxA was 22.0%,and the carrying rate of oqxB was 15.4%.QnrA,qnrB and qnrC were not detected.The detection and identification of the beta lactam resistance gene PCR showed that 50 strains of 123 E.coli strains carry TEM type beta lactamase resistance genes,and the gene carrying rate is 40.7%.4.Detection and identification of virulence genes of E.coli from duck embryosFor 123 E.coli strains,18 kinds of virulence genes were detected by multiple PCR,and42 strains were isolated,which accounted for 34.1%.Among these five genes,yijp,fim C,ISS,ibeB and ompA have a very high detection rate.This investigation provides a theoretical basis for long-term monitoring and research of avian pathogenic E.coli.In this study,E.coli isolated from dead duck embryos of Tai’an duck breeding plant was amplified by PCR.Results showed that 100 of the 123 strains of E.coli had ETT2 pathogenicity islands,with a detection rate of 81.3%.123 strains of duck source Escherichiacoli ETT2 virulence Island were divided into 11 types of A~K,including 1 complete and 10 different degrees of deletion.Among them,the detection rates of B and C type ETT2 virulence island were the highest,and the detection rates were 31.7%(39 strains)and 26.8%(33 strains)respectively.This experiment investigated the distribution of ETT2 virulence island in duck E.coli,and laid a foundation for further studying the pathogenicity mechanism of ETT2 pathogenicity island in duck E.coli.