Diarrheic and septicemic colibacillosis of the neonates and young animals are the most common and devastating bacterial diseases in farm animal industry. Most Escherichia coli strains are commensal inhabitants of the gastraintestinal tract but some strains express virulence factors that enhance their ability to cause a wide variety of intestinal and extraintestinal diseases in calves, lambs, piglets, and human beings.
Besides enterotoxigenic, verotoxigenic, and enteropathogenic E. coli there is evidence of the emergence of other types of pathogenic E. coli.
The so-called NecroToxigenic E. coli (NTEC) which produce the Cytotoxic Necrotizing Factors (CNFS) 1 and 2 must be recognized as a major developping problem on the basis of (i) epidemiological data; (ii) experimental infections in piglets and calves; (iii) activity of CNFs and of NTEC on cell cultures; (iv) association in clusters on the chromosome or on a plasmid of the cnfl and cnf2 genes with genes coding for other putative virulence factors, especially adhesins of the P, 5, F17, and AFA families The research goals of this proposal are: (i) the comparison of NTEC strains from various animal species and human beings at the bacterial and molecular levels; (ii) the definition of the contribution of the CNFs to the pathogenicity of NTEC strains at the molecular, cellular, and wholeanimal levels. In the first part of the proposal, classical and virulence associated properties of NTEC1 and NTEC2 strains, their putative virulence factors and plasmids will be studied and compared by classical and molecular epidemiology techniques. The putative colonization factors will be precisely identified, characterized and compared at the molecular level with already described members of their respective families. Finally the diagnosis of the CNFs in routine diagnostic laboratories will be facilitated by the development of monoclonal antibody-based ELISAs assays In the second part, two different and complementary approaches will be followed to study the contribution of CNFs to the pathogenicity of NTEC strains: (i) in vivo models of infections in germ-free piglets with NTEC strains and in colostrum-deprived calves with NTEC2 strains; and (ii) in vitro models of interaction of NTEC1 and NTEC2 strains with epithelial cell cultures, either HeLa cells or polarized cells. In both in vivo and in vitro models the wild-type NTEC strains will be compared to their isogenic mutants in the cnfl or cnf2 genes, obtained by allelic exchange
Funding SchemeCSC - Cost-sharing contracts
BT4 3SD Belfast
J2S 7C6 Saint-hyacinthe