Start Date: Dec 28, 2010
End Date: Dec 27, 2015
Experimental animal models, tissue cultures, and specific mutants will be used to describe molecular mechanism(s) enabling Escherichia coli (E. coli) O157:H7 bacteria to grow, adhere, and colonize the cattle intestine. Mutant strains lacking one or more of the virulence factors, such as type III secretion, motility, and bacterial cell surface fimbriae, will be constructed and tested in adherence assays using cultured cells and/or bovine intestinal tissues to delineate the importance of these factors in adherence of non-O157 Shiga toxin-producing E. coli (STEC) to these tissues. Reporter gene fusions and global gene analysis technologies will be used to determine effects of host gastrointestinal environment and innate immune system on the expression of specific bacterial genetic systems and metabolic pathways that promote E. coli O157:H7 persistence in cattle intestine. Select group of non-O157 STEC strains will also be examined for the effects of signaling molecules, especially stress hormones norepinephrine or epinephrine, and fermentation products produced in the bovine intestinal tract on the expression of virulence factors and adherence of these STEC strains to bovine intestinal tissues. The focus would be to examine virulence factors that are secreted through the type III secretion system or those expressed on bacterial cell surface for promoting bacterial motility, adherence, and aggregation on bovine intestinal tissues. Emerging non-O157 STEC serotypes will be compared with E. coli O157:H7 to identify genetic and molecular features unique to these serotypes. Bacterial genes or gene products identified in these studies will be used, based on their importance in colonization, for developing whole-cell or protein/subunit protein vaccines for reducing or eliminating E. coli O157:H7 and non-O157 STEC colonization and shedding in cattle.