FIG. 5.

C. rodentium bacteria at day 10 p.i. penetrate deeper into the colonic crypts of iNOS-deficient mice than in wild-type mice. (A) During the course of C. rodentium infection in wild-type C57BL/6 mice, the majority of the bacteria were found attached to superficial epithelial cells (arrowheads) and within the lumen. There is little evidence of bacteria penetrating deeply into colonic crypts. (C) Under higher magnification, one can see individual bacteria (arrowheads) on the surface of these superficial epithelial cells while the base of the crypts are uninfected. (B) In contrast, bacteria infecting iNOS-deficient mice at day 10 p.i. were found to penetrate deeper into crypts, sometimes reaching even the base of the glands. The asterisks identify crypts that are heavily infected with C. rodentium reaching to the base of the crypt. (D) At higher magnification, one can see several crypts filled down to their base with C. rodentium (arrowheads). This effect was transient with the infection in iNOS-deficient mice, again becoming superficial at later time points in the infection. Original magnification for all, ×400.