RESUMO
In order to obtain the serotype distribution of E.coli from duck and to screen the vaccine bacterial strains,the serotype identifications and biological characteristics of E.coli were analyzed in recent years from Shandong,Hebei and other areas of commercial duck field;selections of vaccine strains were detected by the virulence and immunogenicity.Totally 44 isolated bacterial strains of E.coli from duck were identified to a total of six serotypes:O78,O93,O76,O2,O92 and O32.The O78 serotype was the dominant serotype,accounting for 56.8％ (25/44);O93 serotype for 15.9％ (7/44) according to bacterial Oantigen typing.The strain SD (O78 serotype) was confirmed to have strong virulence and good immunogenicity.The O78,O93 and O76 are the dominant serotypes of duck E.coli in the study areas.The SD strain could be used as the candidate for the next development of inactivated vaccine.