Small intestinal bacterial overgrowth is associated to symptoms in irritable bowel syndrome. Evidence from a...

Small intestinal bacterial overgrowth (SIBO) is involved in the pathogenesis of irritable bowel syndrome (IBS). It has been suggested that by treating SIBO in IBS, symptoms may be improved. The aim of this study was to evaluate the prevalence of SIBO in patients with IBS compared with healthy volunteers (HV), to assess the effect of an intestinal antibiotic in eradicating SIBO and on the symptoms, in patients with IBS.

Design: a cross-sectional multicentre study with cohort comparison performed in 6 medical centers from Romania. 331 consecutive patients diagnosed with IBS according to Rome III criteria and 105 HV were screened for SIBO using glucose hydrogen breath test (GHBT). Positive patients received 7 days therapy with the antibiotic rifaximin 1200 mg/day and were retested 1 week after completing the treatment. The IBS symptoms were assessed before and after treatment. The group was controlled with 20 age and sex matched IBS patients who did not receive any antibiotic therapy for their condition (control patients).

SIBO was found in 105 patients with IBS (31.7%) and in 7 HV (6.6%) (OR= 6.5, p < 0.0001). Patients with IBS have been classified according to Rome III criteria into 4 groups: IBS-constipation, IBS-diarrhea, IBS-mixed (alternation of constipation/and diarrhea) and IBS-unclassified. Diarrhea and mixed symptoms were found to be predictive for SIBO (OR= 2.5 for IBS-diarrhea and OR = 2.23 for mixed). Among patients with SIBO, 85.5% were found negative after treatment (p = 0.0026). SIBO patients showed an important relief of their symptoms, with complete improvement in 46.6% and partial in 31.4%.

This study is the first to estimate the prevalence of SIBO in ibs patients from Romania (31.7%). SIBO was present in nearly half of the IBS-D patients (45.7%). Rifaximin is effective in treating SIBO in IBS patients and controlled trials are warranted.