The purpose of this study is three fold: 1)To collect serum from patients with documented Clostridium difficile infection and test for the presence of antibody to C. difficile toxin at the start and at the end of therapy, and again if a relapse or recurrence occurs. 2)To collect stool samples for test of C. difficile toxin at similar time intervals. 3)To assay random serum samples from the VA lab in order to determine the rate of antibody to C. difficile toxin in our patient population.

Clostridium difficile is the leading cause of nosocomial diarrheal disease associated with antibiotic therapy. This is a debilitating condition with substantial morbidity and mortality that may be around 2-3%. Current recommended therapy for this condition is metronidazole, given orally. Our observations suggest that about 10-20% of patients fail to respond to initial therapy with metronidazole, and 20% relapse after treatment. The reason why some persons are cured whereas others relapse is, at present, unknown. There is a suggestion in the medical literature that recurrent infection is associated with the failure to generate antibody to C. difficile toxin. It is also possible that those patients who become infected lack antibody, whereas others in the population tend to have such antibody. The investigators propose to study our patients at VAMC Houston in order to relate occurrence and/or the failure to respond to therapy or the appearance of recurrent disease to the presence of anti-toxin antibody. The investigators also propose to study sera obtained at random from VAMC patients in order to determine the prevalence of antibody in our patient population.

Inclusion Criteria:

• All patients at the Houston VA with documented C. difficile infection

Exclusion Criteria:

• None

Patients positive for C. difficile.