Western
Meeting of Poultry
Clinicians and Pathologists
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Clinicians and Pathologists
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Characterization of Escherichia coli Isolated from Cases of Avian Colibacillosis Brenda J. Allan, Jan V. van de Hurk, and Andrew A. Potter Veterinary Infectious Disease Organization
Escherichia coli infection in turkeys and chickens in manifested in several forms, the most common being colibacillosis. This disease is characterized by septicemia, airacculitis, pericarditis, and perihepatitis. Such infections frequently develop as a secondary even subsequent to infection with another agent or environmental stress. Fifty western Canadian isolates of Escherichia coli associated with colibacillosis of turkeys and chicks were characterized. The isolates belonged to 17 O serogroups, with 42% of the strains being nontypeable. Only six serogroups were represented by more than one isolate. The literature suggests that serogroup O1, O2, and O78 are most common among E. coli isolated from cases of colibacillosis in poultry. In our collection of strains these three serogroups accounted for 20% of the isolates. A high frequency of resistance to tetracycline, kanamycin, neomycin, cephalothin, streptomycin, and erythromycin was observed. Many strains were resistant to several antibiotics, but no pattern predominated. Only wide spread sensitivity to ampicillin and chloramphenicol was also observed. The ability to grow in a low iron environment has been linked to pathogenicity. Of the 50 E. coli strains examined 94% produced aerobactin, a siderophore that aids in the sequestering of iron from the environment. E. coli belonging to serogroups O1, O2, and O78 were tested for the ability to produce high molecular weight iron-regulated outer membrane proteins (IROMPS) that may facilitate the uptake of iron. All strains tested produced two or more IROPMS in response to low iron conditions. All strains produced pili after 72 hours of culture at 37oC and exhibited mannose-sensitive hemagglutination of avian red blood cells. The presence of pili facilitates the initial colonization of the animal by E. coli. The five strains of serotype O1 and O2 were resistant to killing by normal turkey serum. Only 2 of the 5 isolates of serotype O78 were serum resistant. As bacteraemia is a component of colibacillosis the ability to resist killing by normal serum will contribute to the overall pathogenicity of the bacteria. Using the young chick model, it was determined that the 5 strains belonging to serogroups O1 and O2 were highly virulent. The 5 strains belong to serogroup O78 were less virulent. The strains examined exhibit several characteristics that have been associated with pathogenicity. These include the ability to produce pili, production of aerobactin and iron regulated outer membrane proteins, and the ability to resist killing by normal turkey sera. The diversity observed in the O serogroups has been reported for other groups of avian isolates of E. coli. This diversity will necessitate the use of several serogroups in a vaccine to prevent colibacillosis. This work was supported by grants from the Alberta Turkey Growers’ Marketing Board, B.C. Turkey Marketing Board, Manitoba Turkey Producers’ Marketing Board, Saskatchewan Turkey Producers’ Marketing Board, Canadian Turkey Marketing Agency and Alberta Agricultural Research Institute.
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