عنوان

Phenotypic and genetic analyses of P and type 1 fimbriae of pathogenic Escherichia coli from poultry

TLpq304286408

انگلیسی

Phenotypic and genetic analyses of P and type 1 fimbriae of pathogenic Escherichia coli from poultry

[Thesis]

C. M. Dozois

J. M. Fairbrother

Universite de Montreal (Canada)

1995

253

Ph.D.

Universite de Montreal (Canada)

1995

The aim of this study was to identify the virulence factors associated with pathogenic E. coli from poultry colisepticemia and to characterize one group of virulence factors, the fimbrial adhesins. To identify virulence factors associated with avian colisepticemia, E. coli strains from healthy or septicemic poultry were screened phenotypically and genotypically for virulence factors associated with extra-intestinal E. coli from humans and livestock. Presence of pap- and fim (pil)-hybridizing DNA, the aerobactin siderophore system, certain O serogroups (particularly O78 and O1), and serum resistance were more commonly associated with strains from septicemic birds than with E. coli from healthy birds. P fimbrial expression in usdpap\sp+usd strains and the frequency of the detection of the aerobactin system differed considerably between strains from septicemic chickens and septicemic turkeys, suggesting different mechanisms for the development of colisepticemia in these two avian species. To characterize P and type 1 fimbriae of avian pathogenic E. coli, pap strains grown on different media were examined using hemagglutination and immunotechniques. P fimbriae were only produced by a limited number of strains and possessed an 18 kDa major subunit most closely related to the F11 serotype. Type 1 fimbriae from usdpap\sp+/fim\sp+usd E. coli exhibited major fimbrial subunits with a 17 to 18.5 kDa molecular weight. In addition, usdpap\sp+/fim\sp+\ E.\ coliusd from septicemic poultry could be divided into three phenotypic groups based on differences in the expression of type 1 fimbriae when strains were grown on different media. Strains of each of the different phenotypic groups generally belonged to the same serogroup. To explain the lack of expression of P fimbriae by most usdpap\sp+usd strains, we examined the genetic organization of P fimbrial gene clusters in these strains. Differences in the P fimbrial gene content and organization correlated with the P fimbrial phenotypes of the strains. Most of the strains possessed sequences related to the felA gene, which encodes the F11 major subunit. However, only strains expressing P fimbriae contained one complete copy of a P fimbrial gene cluster, whereas P non-expressing strains contained partial or divergent sequences of P fimbrial gene clusters. The roles of type 1 and P fimbriae in the development of avian colisepticemia were investigated by in vivo infection studies and in vitro adherence tests. Type 1 fimbriae were expressed in vivo by bacteria in the trachea and air sacs of infected birds, and mediated in vitro adherence to tracheal tissue sections, suggesting a role for type 1 fimbriae in the colonization of the upper respiratory tract of poultry. P fimbriae, on the other hand, were expressed in vivo in the air sacs, lungs, and blood, but not in the trachea of infected birds and mediated in vitro adherence to air sac and lung sections but not to tracheal tissues. Hence P fimbriae may play a role in the colonization of systemic tissues and in the development of septicemia. (Abstract shortened by UMI.)

Animal diseases

Animal diseases

Biological sciences

Genetics

Microbiology

Molecular biology

C. M. Dozois

J. M. Fairbrother

p

[Thesis]

276903

a

Y