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Small intestinal bacterial overgrowth in patients with irritable bowel syndrome.
  1. Iris Posserud (iris.posserud{at}
  1. Sahlgrenska University Hospital, Sweden
    1. Per-Ove Stotzer
    1. Sahlgrenska University Hospital, Sweden
      1. Einar Björnsson (einar.bjornsson{at}
      1. Sahlgrenska University Hospital, Sweden
        1. Hasse Abrahamsson (hasse.abrahamsson{at}
        1. Sahlgrenska University Hospital, Sweden
          1. Magnus Simren (magnus.simren{at}
          1. Sahlgrenska University Hospital, Sweden


            Background & aims: Small intestinal bacterial overgrowth (SIBO) has been proposed to be common in irritable bowel syndrome (IBS), with altered small bowel motility as a possible predisposing factor. The aim of this investigation was to assess the prevalence of SIBO, using culture of small bowel aspirate, and its correlation to symptoms and motility in IBS.

            Methods: We included 162 IBS patients who underwent small bowel manometry. and culture of jejunal aspirate. Cultures from 26 healthy subjects served as controls. Two definitions of altered flora were used: standard definition of SIBO (≥105 colonic type bacteria/mL), and mildly elevated counts of small bowel bacteria (≥95th percentile in controls).

            Results: SIBO (standard definition) was found in 4% of both patients and controls. Signs of enteric dysmotility were seen in 86% of patients with SIBO and 39% of patients without SIBO (p=0.02). Patients with SIBO had fewer phase IIIs (activity fronts) compared with patients without SIBO (p=0.08), but otherwise no differences in motility parameters were seen. Mildly elevated bacterial counts (≥5x103/mL) were more common in patients compared with controls (43% vs. 12%; p=0.002), but this was unrelated to small intestinal motility. No correlation between bacterial alterations and symptom pattern could be observed.

            Conclusions: Our data do not support an important role for SIBO according to commonly used clinical definitions, in IBS. However, mildly elevated counts of small bowel bacteria seem to be more common in IBS and needs further investigation. Motility alterations could not reliably predict altered small bowel bacterial flora.

            • bacterial overgrowth
            • gastrointestinal dysmotility
            • hydrogen breath test
            • irritable bowel syndrome

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