The investigators propose to study intensively the bacteriology of feces in C. difficile associated diarrheal disease, using a variety of conventional and very up-to-date techniques.

Clostridium difficile associated colitis is an increasing problem in hospitals throughout the developed world; the number of cases has increased, and the failure to respond to conventional therapy has become far more common. The investigators have recently documented in the medical literature (Clin Infect Dis, June, 2005; Lancet Infect Dis, August, 2005). Possible reasons for failure of treatment include persistence of C. difficile and/or imbalance of other bacterial flora in the colon. The bacteriology of fecal flora in C. difficile associated diarrhea has not been studied.

Inclusion Criteria:

• Patients with antibiotic-associated diarrhea with a positive assay for C. difficile toxin
• Patients with antibiotic-associated diarrhea with 3 negative assays for C. difficile toxin
• Patients with antibiotic-associated diarrhea that has failed to respond to conventional therapy
• Hospitalized patients who have received >2 antibiotics and who have no symptoms of diarrhea or abdominal discomfort

Exclusion Criteria:

• none

Patients positive for C. difficile