The Pathogenic Characteristics Of CTX-M Multidrug Resistance Escherichia Coli Isolates From Chicken

Avian pathogenic E.coli is a potential pathogen to humen and animals,including many virulence factors.Resistance gene is one of the main causes of resistance to bacterias.However,the domestic and foreign scholars have a clear controversy on the change trend of pathogenic force after the sensitive bacterias become resistant bacterias.The purpose of this paper is to explore the differences of the pathogenicity among CTX-M-1 chicken E.coli,CTX-M-9 chicken E.coli and non-CTX-M chicken E.coli by analysing the PFGE typing,O antigen serogroups,virulence factors,the relative expression of some virulence factors in vitro study of these three kinds of chicken E.coli.91 of 106 chinkens E.coli strains can be typed by PFGE and they were divided into P1-P46 46 genotypes.Although the phylogenetic relationships are dispersed,the clonal propagation still play a certain role in the spread of the CTX-M genes.The clones of P12 and P3 were dominant clones,which accounted for 13.19% and 8.79%respectively.Comparing with the non-CTX-M strains,the clonal propagation played a more significant role in the CTX-M strains,especially in the CTX-M-9 strains for the reason that there were 53.85%(21/39)PFGE type determined strains belonging to only 4 clones.The 106 strains of chicken E.coli were identificated by 13 kinds of E.coli O antigen factor serum and 55 strains had identification results.O8,O14 and O36 were the popular serotypes in these tested strains.Different CTX-M subsets of chicken E.coli had different dominant serotype.The serotypes of CTX-M-9 isolates in Henan is more complex and variable than the serotypes of CTX-M-1 isolates.There were 3O26 E.coli and 4 O111 E.coli that belonged to shigella toxin-producing E.coli,which may lead to a large area of CTX-M bacterias infection.We explored the epidemiologies of the virulence genes in CTX-M-1 cluster Escherichia coli,CTX-M-9 cluster isolates and non-CTX-M ones by multiplex-PCR.The results showed that all of E.coli contained almost similar virulence genes and the detection rates of feo B,fim H,tra T,and sit A were higher than the others.The CTX-M-1 cluster and the CTX-M-9 cluster E.coli harbored significantly morevirulence factors than non-CTX-M isolates,with the tra T and irp-2 in the CTX-M-1cluster and the iron,iss and irp-2 in CTX-M-9 cluster.Moreover,the partial virulence factors showed significantly difference between the CTX-M-1 cluster and the CTX-M-9 cluster.The cva C and sfa S genes in the former were significantly more than those in the latter,but the iro N and iss genes were significantly fewer.In conclusion,the pathogenicities of CTX-M-producing E.coli maybe more powerful,and the CTX-M genotypes maybe had close relationship with their pathogenicity.The pathogenic of the bacterias not only attributed to the presence of the differents virulence genes but also related to the expression quantities of related virulence genes.In this study,we used fluorescence quantitative PCR method to compare the expression level of iss,iro N in three kinds of bacterias in vitro culture to determine the differences of the pathogenicity between the CTX-M chicken E.coli and non-CTX-M chicken E.coli.Our research results show that although the iss,iro N in CTX-M-9 chicken E.coli were significantly more than those in the CTX-M-1chicken E.coli and non-CTX-M chicken E.coli,but the genes expressions in vitro among these three types of chicken E.coli had no differents.In summary,the 106 strains of E.coli had large number of PFGE serotypes,which meaned that their relationship was distantly.These strains carried a lot of adhesin-related genes,iron-related genes and protectins genes.We had a preliminary understanding of the epidemiology of avian E.coli virulence genes in the Henan areas and had a preliminary understanding of the change trend of pathogenic force after the sensitive bacterias become resistant bacterias.In terms of the types and numbers of virulence factors,the pathogenicity of CTX-M-1 and CTX-M-9 may be stronger than that of the susceptible strains,but the m RNA expression of iss iro N gene in vitro was not different in the 3 kinds of bacterias.