Figure 4. Histopathology in the colon of C. difficile-infected animals during early infection. (A) Colon of a mouse with clinically severe CDI infected with VPI 10463. There is severe submucosal edema accompanied by inflammatory cells within the mucosa and invading the submucosal lymphoid tissue. The epithelial surface is also irregular and eroded. (B) Colon of a mouse infected with BI1 that shows significant submucosal edema and scattered inflammatory cells. (C) Colon of a mouse infected with the 630 strain of C. difficile shows minimal to no histopathological changes. (D) Colon of a mouse colonized with F200 which shows some inflammation but otherwise no significant histopathological changes. HE. All images were the same magnification (x200). Scale bar = 100 µm.