Clinical Isolation Of Avian Escherichia Coli And Analysis Of ETT2 Pathogenicity Island

At present,diseases caused by.coli·are still numerous in poultry diseases,causing economic losses to farmers of all sizes and causing many problems.A newly discovered E.coli.pathogenicity island ETT2.The full name is E.coli type 3 secretion system 2,About 29.9kb in size.ETT2 is likely related to the evolution and pathogenicity of E.coli.Therefore,detection and analysis of ETT2 E.coli will help to study the pathogenicity in E.coli.In this study,the ETT2 gene sequences published in GenBank were used as the reference sequence.ECs3703 and ECs3737 at both ends of ETT2 were selected as detection marker genes.Establish a Duplex PCR assay,Through the testing of 65 farmer samples,among them,48 households(73.8%)were found to have ETT2+E.coli.infection;91(63.2%)were ETT2+ in 144 diseased and dead birds;252 of clinical samples were found to have ETT2+ E.coli.infection of 115(45.6).%);Through the detection of 437 strains of avian E.coli clinical isolates,it was found that ETT2+E.col.was 227(51.9%).In order to detect the gene type of E.coli ETT2 from avian,three pairs of primers were designed according to the Ecs3709,Ecs3712 and Ecs3727 gene sequences in Genbank,and the other 30 pairs of primers for detecting Ecs3704?ECS3736 gene were synthesized by reference.Using the reference strain S451524 as a positive template control,the ETT2 gene types of 227 strains of ETT2+ E.coli.were detected by PCR.The results showed that the avian E.coli.ETT2 can be divided into 10 regular types and other types without special rules;the regular types include A type(12 strains),C type(3 strains),D type(2 strains),E type(16 strains);F type(1 strain),L type(54 strains)are the most abundant type,M type(4 strains),O type(6 strains),Q type(11 strains),P type(5 strains)and others without special patterns(113 strains).In order to detect the integration site of ETT2 in the avian E.coli.genome,according to the ETT2 gene sequences published in Genbank,Ecs3737 was used as the upstream,and the glyU tRNA was a downstream PCR specific primer.Through the detection of 227 strains of ETT2 E.coli,the probability of ETT2 binding to the glyU tRNA locus in the avian E.coli genome was found to be 59%(134 strains).To understand whether there is a correlation between ETT2 and other virulence factors of avian E.coli.In this study,F1 pilus,HPI virulence islands,PAP pilus,and LEE virulence islands were detected in 227 strains of E.coli.with ETT2 and 210 strains of E.coli without ETT2.The results showed that the detection rates of F1 pilus,HPI virulence islands,PAP pilus,and LEE pathogenicity island in ETT2 E.coli were 94.2%(214 strains),36.9%(90 strains),3.5%(8 strains),and 13.7%(31 strains);and the detection rates in E.coli not carrying ETT2 were 60%(127 strains),9%(19 strains),7.6%(16 strains),and 5.7%(12 strains).