title: Attenuation of an avian pathogenic Escherichia coli strain due to a mutation in the rpsL gene.
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 10(6) 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 10(6) CFU of the wild-type strain EC317 was investigated. Vaccination by both aerosol (day 1) and oral (days 14 and 28) routes using 10(8) 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.
authors.affiliation: Veterinary Infectious Disease Organization, 120 Veterinary Road, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 5E3.
authors.forename: K K
authors.initials: KK
authors.lastname: Amoako
authors.forename: T
authors.initials: T
authors.lastname: Prysliak
authors.forename: A A
authors.initials: AA
authors.lastname: Potter
authors.forename: S K
authors.initials: SK
authors.lastname: Collinson
authors.forename: W W
authors.initials: WW
authors.lastname: Kay
authors.forename: B J
authors.initials: BJ
authors.lastname: Allan
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002645:Chickens; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011201:Poultry Diseases / Q000382:microbiology / Q000517:prevention & control; D000091243:Ribosomal Protein S9; D013307:Streptomycin / Q000494:pharmacology; D014611:Vaccination / Q000662:veterinary; D014774:Virulence / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D000091243:Ribosomal Protein S9; C000717190:RpsI protein, E coli; D013307:Streptomycin