Role of gut microflora and probiotic effects in the irritable bowel syndrome

Acta Biomed. 2006 Aug;77(2):85-9.


Background: Even though the cause of irritable bowel sindrome (IBS) is not yet known, alterations of the intestinal microflora may be important in its pathogenesis.

Aim: To evaluate the efficacy of rifaximine alone or in association with the probiotic strain of Bifidobacterium longum W11 in reducing symptoms in patients with IBS.

Methods: We performed a monocentric, prospective, randomized open trial including 70 patients randomized in to two groups: Group A (41 patients) receiving rifaximin 200 (2 cp bid for ten days in a month) followed by a formulation of the probiotic strain of Bifidobacterium longum W11(one granulated suspension for 6 days on alternate weeks ) and Group B (29 patients) receiving only rifaximin 200 (2 cp bid for ten days in a month). The clinical evaluation was performed at admission and after 2-months, taking into account the method of visual analogous.

Results: At the 2-month follow-up, Group A patients reported a greater improvement of symptoms compared to patients in group B (p = 0.010) even if the physician's opinion at T1 did not confirm these results (p = 0.07).

Conclusion: The increased colonisation by Bifi-dobacterium longum W11, after the cyclic administration of rifaximin, which eradicates the bacterial overgrowth of the small intestine, may reduce symptoms, especially those related to bowel habit and stool frequency in patients with IBS. The abnormalities observed in the colonic flora of IBS suggest, in fact, that a probiotic approach will ultimately be justified.

Publication types

  • Comparative Study
  • Evaluation Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Anti-Infective Agents / administration & dosage
  • Anti-Infective Agents / therapeutic use*
  • Bifidobacterium*
  • Data Interpretation, Statistical
  • Drug Therapy, Combination
  • Female
  • Follow-Up Studies
  • Gastrointestinal Agents / administration & dosage
  • Gastrointestinal Agents / therapeutic use*
  • Humans
  • Irritable Bowel Syndrome / diagnosis
  • Irritable Bowel Syndrome / microbiology*
  • Irritable Bowel Syndrome / physiopathology
  • Male
  • Middle Aged
  • Probiotics / therapeutic use*
  • Prospective Studies
  • Rifamycins / administration & dosage
  • Rifamycins / therapeutic use*
  • Rifaximin
  • Time Factors
  • Treatment Outcome


  • Anti-Infective Agents
  • Gastrointestinal Agents
  • Rifamycins
  • Rifaximin