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1 January 2004 Attenuation of an Avian Pathogenic Escherichia coli Strain Due to a Mutation in the rpsL Gene
K. K. Amoako, T. Prysliak, A. A. Potter, S. K. Collinson, W. W. Kay, B. J. Allan
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Abstract

The diseases caused by pathogenic Escherichia coli constitute a major economic loss to the poultry industry. The development of a live oral E. coli vaccine to prevent or reduce diseases in poultry had been the objective of our work. Four spontaneous streptomycin-dependent (str-dependent) mutants were generated from a virulent avian strain that contains a mutation in the fur region of the chromosome. Genetic analysis of the mutants indicated that the str-dependent phenotype was due to a base change of C → T at base 272 in the rpsL gene. The mutants were tested for attenuation using the day-old chick model. Day-old birds, in groups of 20, were either challenged with 106 colony-forming units (CFU) of the str-dependent mutant, the parent strain (containing the fur mutation), or the wild-type strain without the fur mutation. The parent strain and the wild-type strain were highly virulent, and 80% or more of the birds died. None of the birds challenged with the str-dependent mutants died, indicating attenuation of the mutants. The protective effect of the mutant as a live vaccine against the challenge with 106 CFU of the wild-type strain EC317 was investigated. Vaccination by both aerosol (day 1) and oral (days 14 and 28) routes using 108 CFU of the str-dependent mutant (EC1598) had no effect on the occurrence of cellulitis in the birds. Two vaccinations given as aerosol on day 1 and given orally on day 14 also had no significant effect on the occurrence of systemic lesions. Three immunizations on days 1, 14, and 28 resulted in a significant reduction in the number of birds with systemic lesions. Antibody titers prior to challenge were not predictive of outcome of challenge.

K. K. Amoako, T. Prysliak, A. A. Potter, S. K. Collinson, W. W. Kay, and B. J. Allan "Attenuation of an Avian Pathogenic Escherichia coli Strain Due to a Mutation in the rpsL Gene," Avian Diseases 48(1), 19-25, (1 January 2004). https://doi.org/10.1637/6025
Received: 1 July 2002; Published: 1 January 2004
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