FIG. 4.

SEM images of cecal tissue infected with C. difficile. Tissues were obtained 1 h after the onset of diarrhea (approximately 29 h postinfection for B1 and approximately 44 h postinfection for 630). (A) Control uninfected tissue. (B and D) Infection of the tissue with both 630 (B) and B1 (D) resulted in denuded patches of microvilli (open arrows), and organisms appeared to anchor themselves to the mucosal surface. (C and E) For 630, attachment was mediated largely at the pole of the organism (C), while for B1, the organisms appeared to be interacting with the surface by means of pilus-like structures between 200 and 300 nm long (E) (arrow). (F) Higher magnification of pilus-like structures in panel E (arrows).