Abstract
Promoter alterations in the csgD gene of Escherichia coli O157:H7 strains ATCC 43894 and ATCC 43895 are associated with variations in curli expression and the ability to bind Congo red dye. Red variants of each strain were more invasive for cultured HEp-2 cells than were white variants. An ATCC 43895 red variant was more virulent than a white variant in a mouse model. However, there were no differences in Shiga toxin production between red and white variants.