| E.coli is a Gram-negative bacillus with a wide range of hosts,divided into symbiotic and pathogenic bacteria.Pathogenic E.coli is the leading cause of diarrhea,global foodborne disease outbreaks,and various parenteral infections.Donkeys are one of the hosts of E.coli,and diarrhea or mastitis is observed in infected donkeys,which seriously affects large-scale farming of donkeys.1.Isolation and identification of diarrhea donkey foal pathogens332 samples were collected in 20 large-scale donkey farms in Liaocheng,Shandong Province from December 2017 to October 2019,including 220 intestinal contents and 112 anal swabs.The obtained samples were identified by the XK bacteria identification instrument,and 196 of the 334 samples were E.coli,and it was selected and cultured on Mac Conkey agar medium and eosin blue medium,Observation of the purified bacteria sample with electron microscope,the shape was medium-sized rod-shaped bacteria.Red short rod-shaped colonies,no spores,obtuse at both ends,distributed individually or in pairs were observed by Gram STaining,and conform to E.coli Morphological characteristics.Ten samples of escherichia coli were intraperitoneally injected,all of which could cause different degrees of morbidity or mortality in mice.Tests showed that most of the samples were pathogenic escherichia coli.2.Detection and analysis of virulence factors in E.coli30 E.coli strains virulence factors were explore,and the positive rate was respectively OMPA(73%),sfa D(77%),tra Ta(73%),the STa(67%),EAST1(67%),amadeus(63%),ksp II(60%),irp2(73%),iuc D(57%),the eae A(57%)and VAT(47%),the iss(33%),cva(27%),ETT2(73%),K88(60%).The virulence factor gene profile test showed that the significant differences in virulence genes were observed in the 30 E.coli,with up to 13 virulence genes,and surpassing 10 virulence genes were appear in 9 E.coli strains.The results may be explained that most of the E.coli isolated from the diarrhea colt carried multiple virulence factors and the pathogenicity was high.3.Whole genome analysis of E.coliIn this study,p E.Coil La18 strain was selected for whole genome sequencing,and the sequencing sequences were compared and analyzed.The G+C sequence contains 51%content and is predicted to contain 4,544 genes,including 3,247 genes with a length greater than 500 bp and 1,626 genes with a length greater than 1000 bp,with an average gene length of 913 bp.It can be found that the virulence factors fep B,ent C,fep A,fep D,ent B,fep C,and omp A all match more than 99% by virulence factor screening.These virulence factors were mainly mapped to Escherichia coli CFT073 and Escherichia coli O18: K1:H7 str.RS218 bacterium.Analysis of virulence factors showed that the clinically obtained strain was more likely to be Escherichia coli CFT073.Sugar transfer and hydrolysis were mainly process which the genes of pathogenic bacteria involve by analysis of carbohydrate active enzyme.The pathogen host interaction results showed that this strain may evolve in the direction of weakening and loss of virulence.The strain used in this study was closest to Escherichia＿coli＿O15＿H18＿str.＿K1516:1446601 by evolutionary tree analysis.Cluster analysis showed that the evolution direction of the strains in this study was similar to that of the Escherichia＿coli＿UMEA＿3151＿1 strain. |
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