What is the difference between the use of one drug (Oral Metronidazole) versus the use of this same drug combined with another drug (Rifampin) in treatment of bacteria and infection-associated diarrhea in patients? This infection is an important cause of morbidity and mortality in both the community and hospitals, and the leading cause of hospital and chronic facility-acquired diarrhea. Research is important for the treatment of this infection. Patient care with use of two medication treatment regimens will be studied.

Clostridium difficile infection contributes to both community and hospital acquired morbidity and mortality. Metronidazole alone is usually considered the drug of choice, however, frequent relapses occur at a rate of 10-40%. The purpose of this study is to address the use of a combined drug regimen treatment (Metronidazole and Rifampin) for the treatment of CDAD. These drugs used together have been successful. Objectives are to determine the time (days) to resolution of symptoms in each treatment arm; to measure clinical relapse rates; and to assess adverse reactions related to treatment.

Inclusion Criteria:

• Inpatients + outpatients diagnosed with CDAD based on SHEA definition [Laboratory confirmation for presence of C.difficile toxin using enzyme immunoassay and no other etiology for diarrhea + Presence of 1 or more of the following: diarrhea (6 watery stool over 36 hours or 3 unformed stools in 24 hours for at least 2days), pseudomembranes at endoscopy].

Exclusion Criteria:

• Age < 14 yr
• Known hypersensitivity to metronidazole, rifampin
• Receiving medication(s) with potential significant drug interaction with rifampin
• Active liver disease as indicated by ALT > 200 U/L
• Adynamic ileus
• Toxic megacolon
• Pregnancy