Small intestinal bacterial overgrowth is associated with irritable bowel syndrome and is independent of proton pump inhibitor usage

BACKGROUND: Current knowledge suggests that small intestinal overgrowth participates in the pathogenesis of irritable bowel syndrome. It is questionable if this association is modulated by intake of proton pump inhibitors (PPIs). METHODS: In a prospective study, quantitative cultures of duodenal aspirates were performed for aerobic species in 897 consecutive patients undergoing upper GI tract endoscopy. SIBO was defined as equal to or more than 10(3) cfu/ml. The effect of PPI intake on the relationship between SIBO and IBS was the primary endpoint. RESULTS: Analysis among patients without any history of PPI intake (n = 713) showed that odds ratio (OR) for IBS in the event of SIBO was 5.63 (3.73–8.51, p < 0.0001); this was 4.16 (1.91–9.06) when analysis was done among patients with history of PPI intake (n = 184, p: 0.498 between patients without and with PPI intake). Multiple logistic regression analysis found that factors independently associated with SIBO were age above or equal to 60 years (OR: 2.36), body mass index more than or equal to 22 kg/m(2) (OR: 0.60), presence of IBS (OR: 6.29), type 2 diabetes mellitus (OR: 1.59) and gastritis (OR: 0.47). CONCLUSIONS: The association between IBS and SIBO was completely independent from PPI intake. Although gastritis was protective against SIBO, results show that PPI intake cannot prime SIBO.