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The Prevalence of Overgrowth by Aerobic Bacteria in the Small Intestine by Small Bowel Culture: Relationship with Irritable Bowel Syndrome

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Many studies have linked irritable bowel syndrome (IBS) with small intestinal bacterial overgrowth (SIBO), although they have done so on a qualitative basis using breath tests even though quantitative cultures are the hallmark of diagnosis. The purpose of this study was to underscore the frequency of SIBO in a large number of Greeks necessitating upper gastrointestinal (GI) tract endoscopy by using quantitative microbiological assessment of the duodenal aspirate.


Consecutive subjects presenting for upper GI endoscopy were eligible to participate. Quantitative culture of aspirates sampled from the third part of the duodenum during upper GI tract endoscopy was conducted under aerobic conditions. IBS was defined by Rome II criteria.


Among 320 subjects enrolled, SIBO was diagnosed in 62 (19.4%); 42 of 62 had IBS (67.7%). SIBO was found in 37.5% of IBS sufferers. SIBO was found in 60% of IBS patients with predominant diarrhea compared with 27.3% without diarrhea (P = 0.004). Escherichia coli, Enterococcus spp and Klebsiella pneumoniae were the most common isolates within patients with SIBO. A step-wise logistic regression analysis revealed that IBS, history of type 2 diabetes mellitus and intake of proton pump inhibitors were independently and positively linked with SIBO; gastritis was protective against SIBO.


Using culture of the small bowel, SIBO by aerobe bacteria is independently linked with IBS. These results reinforce results of clinical trials evidencing a therapeutic role of non-absorbable antibiotics for the management of IBS symptoms.

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The study was funded in part by a kind donation by Vianex SA, Greece. The study was funded in part by an unrestricted educational grant by Alfa Wassermann, Alanno, Italy.

Conflict of interest

E.P, E.J.G.B., D.T., V.K. and C.B. have no conflict of interest to declare in relationship with this submission. M.P. is funded by the Beatrice and Samuel A. Seaver Foundation, he is a consultant for Salix Pharmaceuticals, has grant funding from Salix Pharmaceuticals and Cedars-Sinai Medical Center has a licensing agreement with Salix.

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Correspondence to Evangelos J. Giamarellos-Bourboulis.

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Pyleris, E., Giamarellos-Bourboulis, E.J., Tzivras, D. et al. The Prevalence of Overgrowth by Aerobic Bacteria in the Small Intestine by Small Bowel Culture: Relationship with Irritable Bowel Syndrome. Dig Dis Sci 57, 1321–1329 (2012).

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