Abstract
Altered bacterial composition and small intestinal bacterial overgrowth (SIBO) may be associated with irritable bowel syndrome (IBS). This study aimed to determine the fecal and mucosa-associated bacterial composition along the gastrointestinal (GI) tract and to assess SIBO in IBS. Bacterial composition of feces, and mucosa of the duodenum and sigmoid colon was determined by 16S rRNA-amplicon-sequencing. SIBO was evaluated by bacterial culture of duodenal aspirate, glucose and lactulose breath tests. Mucosal antibacterial gene expression was assessed by PCR Array. The bacterial profiles of feces and the mucosa of sigmoid colon, but not duodenum, differed between IBS patients (n = 17) and HS (n = 20). The IBS specific bacterial profiles were linked to the colonic antibacterial gene expression. Fecal bacterial profile differed between IBS subtypes, while the mucosa-associated bacterial profile was associated with IBS symptom severity and breath tests results at baseline (H2 and/or CH4 ≥ 15 ppm). The prevalence of SIBO was similar between IBS patients and HS. This study demonstrates that alterations in the bacterial composition of the sigmoid colon of IBS patients were linked to symptoms and immune activation. While breath tests reflected the mucosa-associated bacterial composition, there was no evidence for high prevalence of SIBO or small intestinal bacterial alterations in IBS.
Highlights
Irritable bowel syndrome is a chronic functional bowel disorder which affects around 6% of the population[1]
The majority of studies reporting high prevalence of small intestinal bacterial overgrowth (SIBO) in irritable bowel syndrome (IBS) patients are based on results from glucose and lactulose breath tests[2], measuring the amount of hydrogen and methane produced by bacteria after digestion of ingested fermentable sugars, but do not include quantification of bacteria
Fewer correlations between the expression of antimicrobial genes (n = 2 and n = 11, respectively) and mucosa-associated or fecal bacteria were found in healthy (Fig. 5b,d). This exploratory study demonstrated an altered bacterial composition in the colon of IBS patients compared to healthy subjects, where differences in both fecal and mucosal samples were detected
Summary
Irritable bowel syndrome is a chronic functional bowel disorder which affects around 6% of the population[1]. Previous results from our group showed a subset of IBS patients with an altered bacterial composition in feces[9,10], and that the mucosa-associated bacterial composition of the colon in IBS patients was linked to mucosal low-grade immune activation[11,12]. In this study we hypothesized that IBS patients have an altered bacterial composition in the small and/or large intestine, which in turn is associated with the symptom pattern and the hosts intestinal immune response. The aim of this study was to determine the bacterial composition of fecal samples and biopsies from the small and large intestine, respectively, and to determine the link to symptom pattern and intestinal immune response in IBS patients. This study aimed to explore the consistency between evaluation methods for SIBO and to explore the accordance between breath test results and intestinal bacterial composition
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