Hydrogen Breath Test an Instrument to Predict Rifaximin-Response in Irritable Bowel Syndrome Predominant Diarrhea

Rifaximin will be given during weeks 2-4

Subjects will undergo glucose and lactulose hydrogen breath tests for Small Intestinal Bacterial Overgrowth (SIBO) on consecutive days using a commercially available home base kits (Glucose Hydrogen Breath Test Collection Kit and Lactulose Hydrogen Breath Test Collection Kit for SIBO from Commonwealth Diagnostic International) prior to Rifaximin treatment and at week 13 of the study.