Immunogenicity Of Type Ⅰ Fimbriae Of Avian Pathogenic E.coli And Cloning And Nucleotide Sequence Analysis Of FimA And FimH Gene

107 avian pathogenic E.coli strains were isolated from Shandong province, of which 16 high pathogenic E.coli strains were identified for serum type ,and most strains of serum type was O78.By hemagglutination and PCR analyze, 16 isolates mainly expressed type 1 pili. The results showed that after 72 hours of incubation,pili can be expressed well.Shaker cultures were observed to have an increased growth of pili compared with the stationary cultures.The molecular weight of pili was about 17KDa.Three high pathogenic avian E.coli(O2,O78,O24) isolates ,which had been identified type â… pili by MSHA and PCR,were used to prepare fimbriae vaccines.Some chickens were vaccinated once on one day-old , another chickens vaccinated twice on one day-old and 14 day-old,respectively.Then challenged with E.coli(O2,O78,O24) via the air sac on 4 week-old. The results was that the chickens can efficiently resist attack of homologous E.coli via the air sac,and vaccinated twice with pili vaccine was good at vaccinated once.Cross-protection experiment showed that the pili of the three isolates had certain cross protection.Chickens vaccinated with multivalent pili oil-emulsified vaccine can efficiently resist attack of three homologous E.coli(O2,O78,O24) via the air sac.According to the published type 1 pili FimA nucleotide sequences of avian E.coli,two pairs of primers were designed and synthesized.Fourteen 549bp products were amplificated by polymerse chain reaction(PCR) Two ofthe which were cloned into pMD-18-T vectors, respectively.By analysis of the nuleotide sequences,the homologies of the two strains was 99.8ï¼….The homologies of the FimA gene of two isolates with published type 1 nucleotide sequences of avian E.coli was 92.9ï¼…~100ï¼…. Using two pairs of primers designed according to the published sequences,the FimH genes of three isolates which had been identified type â… pili by MSHA and PCR were obtained through PCR method.The amplified products of 839bp in length were cloned into pMD-18-T vectors, respectively.The analysis of the nuleotide sequences and its deduced amino acid sequences revealed that the homologies of the three isolates' FimH genes was 99.6ï¼… ~99.9ï¼…; the homologies of duced amino sequences of the three was the same; the homologies of the three isolates' FimH with published type 1 pili FimH gene nucleotide sequences of avian E.coli was 97.9ï¼… ~ 100ï¼….