E. coli O157 adherence to squamous and columnar epithelium at the RAJ in experimentally inoculated E. coli O157-positive cattle. Immunoperoxidase (IP), immunofluorescence (IF) and immunogold (IG) labeled RAJ tissue sections are shown. In the IP stained sections (40x magnification), epithelial cells are blue and E. coli O157, brown. In the IF stained sections (20x magnification), epithelial cells are orange-red with blue nuclei, and E. coli O157 are green. IG micrographs are shown at 6800x, 23000x, 9300x, 49000x magnifications, respectively, with E. coli O157 encased in 10 nm colloidal gold label. C, columnar epithelium; S, stratified squamous epithelium; O, E. coli O157. Arrows indicate examples of adhering E. coli O157.