| This article mostly dealt the predominant serogroups of pathogenic E.coli and its distribution in environment of a large farm, tried to find out the transmission sources of avian pathogenic E.coli, in order to focus on prevention and control of avian colibacillosis. So we sampled from the diseased birds associated with avian colibacillosis in twenty-eight factories of that farm, and pathogen isolation, cultivation and identification were also done from the year 2000 to the year 2002.The year 2000, isolated 87 isolates, serogrouped 65 ones, of these isolates there were O78 twenty isolates, fifteen O1 isolates, five 01 isolates, the three serogroupss were the predominant ones of the year; The year 2001 isolated 244 isolates, serogrouped 218 isolates, of these isolates, there were ninety-five 078 isolates, thirteen O91 isolates thirteen O107 isolates, nine 036 isolates, the four serogroups were the predominant serogroups of the year; The year 2002, isolated 113 isolates, serogrouped 87 isolates, of these isolates there were thirty-seven O78 isolates, twenty-five O2 isolates, eight O15 isolates, The three sereogroups were the predominant serogroups the year.The relative pathogenicity of 108 E.coli isolates belonged to predominant serogroups of each year was evaluated in 1-day-old susceptible chicken. Six birds per isolate were inoculated intratracheally with 0.1 ml of a 24-hour-Luria-Bertani (LB) broth culture containing 107 colony forming units (CFU) of E.coli. Based on mortality and lesions examined during a 7-day postinoculation period, 85.18%, 7.41%, 71.41% of the isolates were characterized as high, intermediate and low pathogenicity respectively. The results suggested that 92.6% of these isolates were intermediate or high pathogeincity.Antibiotic sensitivity test of 102 isolates which isolated in the year 2000 to 14 kinds antimicrobial agents which are frequently used in the poultry industry showed that Chloraphenical, Gentamicin, Kanamycin and Spectinomycin were highly efficacious, and high sensitive isolates were more than 80 percent.48 strains isolated from 115 dead chicken embryos in late hatching period, among which we determined 33 isolates belonged to 10 serogroups. The predominant serogroups were O128 and O93.The O serogroup identification of E.coli isolated from different sources showed theO serogroups distribution as follow: From atmosphere we isolated 235 isolates, serogrouped 176 ones, of these isolates there were twenty-five O6 isolates, twenty O21 isolates, twenty O4 isolates, fourteen O38 isolates, fourteen O93 isolates, eleven O78 isolates, these serogroups were predominant ones of atmosphere. From the clocal swap samples of diseased birds we isolated 66 isolates, serogrouped 54 ones, of these isolates there were eight O6 isolates, five isolates O4, four isolates O2, four isolates O107, the four srogroups were the predominant ones of clocal swaps from diseased birds. From the clocal swap sample of healthy bird we isolated 66 isolates, serogrouped 49 isolates, of these isolates there were eight isolates O4, seven isolates 015, seven isolates O2, five isolates O6, these four serogroup were the predominant ones originated from health birds. From the drunken water we isolated 124 isolates, serogrouped 89 ones, of these isolates there were twenty isolates O2, nineteen isolates O9, ten isolates O4, these three serogroups were were the predominant ones distributed in drunken water. From nest material we isolated 139 isolates, serogrouped 1 Bones, of these isolates there were twenty-three isolates O4, seventeen isolates O2, nine isolates O10, eight isolates O20, these were the predominant ones from nest material. From the diseased bird in the environment, we isolated 60 isolates, serogrouped 53 ones, of these isolates there were twenty-eight O78 isolates, nine isolates O2, seven isolates O15, four isolates O6, these were the predominant ones originated from diseased birds in this environment.The relative pathogenicity of same serogrop E.coli isolates from different sources was e... |
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