Small intestinal bacterial overgrowth produces symptoms in irritable bowel syndrome which are improved by rifaximin. A pilot study.

AIM: Searching for the role of small intestinal bacterial overgrowth (SIBO) in the pathogenesis of mechanisms and symptoms in patients with irritable bowel syndrome (IBS).

METHOD: 72 patients with IBS according to Rome III criteria were screened for proximal small intestinal bacterial overgrowth by glucose hydrogen breath test (GHBT). Positive patients received a 14 day therapy with the antibiotic rifaximin 1200 mg/day and were retested 1 week after completing the treatment.

RESULTS

SIBO was found in 8 patients out of 72 (11.1%) All patients receiving rifaximin according to an open label protocol and retested 1 week after the end of treatment were found negative for SIBO 85.7% . Simultaneously the symptoms of IBS improved, according to the measurement by a Likert scale. Patients with IBS-D had a 5.6 RR of presenting SIBO than non IBS-D.

CONCLUSIONS

Rifaximin effectively normalized the GHBT and reduced the IBS symptoms by possibly counteracting the SIBO. Whether such therapeutic approach is ultimately associated with symptom improvement in the long term, however, requires additional studies.