The small (0.5-0.75 um) Clostridial endospores are highly resistant to solvents, acids, bases, radiation, heat, cold, pressure, vacuum and most sporicides. C.difficile causes antibiotic induced pseudomembranous colitis, and is responsible for almost 20% of nosocomial diarrheas in todays hospitals. These endospores have been found on hospital floors, sheets and bedding, as well as on the hands and white coats of hospital personnel.

Our previous studies revealed that these endospores attach to agar by using a two phase attachment process. To examine if this mechanism for spore attachment is also responsible for C.difficile pathogenesis in the human colon, spore attachment and invasion of monolayers of human colon carcinoma cells (Caco-2 cells) using two strains of C.difficile,(ATCC 43594 an isolate from a patient with pseudomembranous colitis [FIG.1A] and ATCC 9689 a clinical microbology laboratory quality control strain) was studied. Cell monolayers grown on 6mm coverslips were inoculated with 10 ul of spore suspension (0.5 McFarland turbidity in sterile water),