Patient description: A 17 year old boy complains of vomiting, non-bloody diarrhea, abdominal pain, fever, chills and loss of appetite for the past 3 days. He ate a salad at a restaurant prior to his diarrhea onset. Physical exam was remarkable for pallor, jaundice, and diffuse abdominal tenderness. Lab results were as follows: Hemoglobin: 9.7 g/dL Platelet: 110,000 /cu.mm Creatinine: 3.6 mg/dL blood urea nitrogen (BUN): 73 mg/dL direct bilirubin: 2.4 mg/dL lactate dehydrogenase (LDH): 881 IU/L (normal: 110-265 IU/L) Peripheral blood smear showed a moderate number of schistocytes and helmet cells. Shiga-like toxin-producing E. coli (STEC) stx1/stx2 were found in stools. He has no other underlying disease and he is not on any medications.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Clostridium Difficile Age ≥ 18 years In-patients with new onset of colitis evidenced by diarrhea (≥3 unformed stools within 24 hours), with one or more of the following: abdominal pain or cramps; peripheral leukocytosis, otherwise unexplained; or fever, otherwise unexplained C. difficile toxin A or B detected in a stool specimen obtained within 7 days before enrollment by enzyme immunoassay Patients able to take oral medications Patients willing to avoid the following medications during the study: oral and intravenous metronidazole, oral vancomycin, anti-peristaltic drugs, opiates, Saccharomyces cerevisiae (baker's yeast), Lactobacillus GC, cholestyramine or colestipol. [Patients on opiates may be included in the study as long as they were taking opiates prior to enrollment and the dose is not increased during the study] Patients willing to abstain from alcohol during the 10-day treatment duration and for two days following treatment  Patients with other known causes of diarrhea or colitis (e.g., Shigella, Salmonella, Cryptosporidium parvum, Giardia lamblia, Entamoeba histolytica, inflammatory bowel disease, irritable bowel syndrome, advanced AIDS or chemotherapy for malignancy) Use within 1 week of enrollment of any drug or therapy with anti-C. difficile activity such as oral or intravenous metronidazole and oral vancomycin. [Patients that have taken up to 2 doses of metronidazole or vancomycin can be included in the study] Females of child bearing age who are either pregnant, breast-feeding or not using birth control. A double barrier method, oral birth control pills administered for at least 2 monthly cycles prior to study drug administration, an IUD, or medroxyprogesterone acetate administered intramuscularly for a minimum of one month prior to study drug administration are acceptable methods of birth control for into the study. In addition, female patients of child-bearing potential should have a baseline pregnancy test and should agree to continue an acceptable method of birth control for the duration of the study (including follow-up) Patients taking phenytoin, celecoxib, and/or losartan. [Patients taking Coumadin® (warfarin) may be included as long the prothrombin time is monitored at least twice weekly during the first 2 weeks of the study and at least weekly thereafter] Patients with severe renal or hepatic impairment Patients who are clinically unstable (e.g., patients with signs of toxic megacolon or imminent perforation) Serious systemic disorders incompatible with the study History of hypersensitivity to metronidazole