Irritable Bowel Syndrome and the Small Intestinal Microflora. What Do We Know?

Irritable bowel syndrome, one of the most common functional gastro intestinal disorders all over the world is considered to have a multi factorial pathogenesis. Recently more and more studies are focusing on the changes that take place in the microbiota of patients with irritable bowel syndrome, underlining the bacterial role in this pathogenesis. As a consequence, bacterial overgrowth, along with intestinal dysmotility, altered brain-gut axis and genetic factors are considered part of this pathophysiology. This report intends to summarize the actual knowledge on irritable bowel syndrome and small intestinal bacterial overgrowth syndrome, from details on the epidemiology, clinical manifestation, pathophysiology, diagnosis, treatment to details on the relationship between these two syndromes.

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

BACKGROUND AND AIMS: 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. METHODS: 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). RESULTS: 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%. CONCLUSIONS: 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.

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.