Original Article

Digestive Diseases and Sciences

, Volume 57, Issue 5, pp 1321-1329

First online:

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

  • Emmannouil PylerisAffiliated withDepartment of Gastroenterology, Sismanogleion General Hospital
  • , Evangelos J. Giamarellos-BourboulisAffiliated with4th Department of Internal Medicine, University of Athens, Medical School4th Department of Internal Medicine, ATTIKON University Hospital Email author 
  • , Dimitrios TzivrasAffiliated with4th Department of Internal Medicine, University of Athens, Medical School
  • , Vassilios KoussoulasAffiliated withDepartment of Gastroenterology, Sismanogleion General Hospital
  • , Charalambos BarbatzasAffiliated withDepartment of Gastroenterology, Sismanogleion General Hospital
  • , Mark PimentelAffiliated withGI Motility Program, Cedars-Sinai Medical Center

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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.


Irritable bowel syndrome Intestinal bacterial overgrowth Diabetes mellitus Proton pump inhibitors