title: Role of virulence factors in resistance of avian pathogenic Escherichia coli to serum and in pathogenicity.
abstract: In chickens, colibacillosis is caused by avian pathogenic Escherichia coli (APEC) via respiratory tract infection. Many virulence factors, including type 1 (F1A) and P (F11) fimbriae, curli, aerobactin, K1 capsule, and temperature-sensitive hemagglutinin (Tsh) and plasmid DNA regions have been associated with APEC. A strong correlation between serum resistance and virulence has been demonstrated, but roles of virulence factors in serum resistance have not been well elucidated. By using mutants of APEC strains TK3, MT78, and chi7122, which belong to serogroups O1, O2, and O78, respectively, we investigated the role of virulence factors in resistance to serum and pathogenicity in chickens. Our results showed that serum resistance is one of the pathogenicity mechanisms of APEC strains. Virulence factors that increased bacterial resistance to serum and colonization of internal organs of infected chickens were O78 lipopolysaccharide of E. coli chi7122 and the K1 capsule of E. coli MT78. In contrast, curli, type 1, and P fimbriae did not appear to contribute to serum resistance. We also showed that the iss gene, which was previously demonstrated to increase resistance to serum in certain E. coli strains, is located on plasmid pAPEC-1 of E. coli chi7122 but does not play a major role in resistance to serum for strain chi7122.
authors.affiliation: Département de Pathologie et Microbiologie, Faculté de Médecine Vétérinaire, Université de Montréal, St. Hyacinthe, Québec J2S 7C6, Canada.
authors.forename: Melha
authors.initials: M
authors.lastname: Mellata
authors.forename: Maryvonne
authors.initials: M
authors.lastname: Dho-Moulin
authors.forename: Charles M
authors.initials: CM
authors.lastname: Dozois
authors.forename: Roy
authors.initials: R
authors.lastname: Curtiss
authors.forename: Peter K
authors.initials: PK
authors.lastname: Brown
authors.forename: Pascal
authors.initials: P
authors.lastname: Arné
authors.forename: Annie
authors.initials: A
authors.lastname: Brée
authors.forename: Clarisse
authors.initials: C
authors.lastname: Desautels
authors.forename: John M
authors.initials: JM
authors.lastname: Fairbrother
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000235:genetics / Q000378:metabolism; D001770:Blood Bactericidal Activity; D002645:Chickens / Q000382:microbiology*; D004926:Escherichia coli / Q000254:growth & development / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000276:immunology / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D009154:Mutation; D011201:Poultry Diseases / Q000276:immunology* / Q000382:microbiology; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides; D037521:Virulence Factors