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

Rom J Intern Med. 2013 Jul-Dec;51(3-4):143-7.


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.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Anti-Infective Agents / therapeutic use*
  • Bacterial Infections / complications
  • Bacterial Infections / drug therapy*
  • Blind Loop Syndrome / drug therapy*
  • Breath Tests / methods
  • Female
  • Hospitals, University
  • Humans
  • Intestine, Small / drug effects*
  • Intestine, Small / microbiology
  • Irritable Bowel Syndrome / drug therapy*
  • Irritable Bowel Syndrome / microbiology
  • Male
  • Middle Aged
  • Pilot Projects
  • Rifamycins / therapeutic use*
  • Rifaximin
  • Treatment Outcome


  • Anti-Infective Agents
  • Rifamycins
  • Rifaximin