Table 2.

Evidence for a Role for the Gut Flora in Irritable Bowel Syndrome

1. Direct evidence of an altered gut microbiota Postinfectious irritable bowel syndrome Small intestinal bacterial overgrowth Altered colonic microbiota

2. Evidence of physiologic effects of an altered microbiota Alterations in the microbiota leading to an increase or decrease in bile salt deconjugation – Changes in stool volume/consistency Alterations in the microbiota leading to an increase or decrease in bacterial fermentation – Alterations in gas volume/composition

3. Mediator of a proinflammatory state

4. Therapeutic impact of altering the microbiota Antibiotics Probiotics Prebiotics