Fecal Microbiota Alterations Associated With Diarrhea-Predominant Irritable Bowel Syndrome

Abstract

Altered gut microbiota are assumed to be involved in the pathogenesis of irritable bowel syndrome (IBS). However, gut microbiota alterations reported in different studies are divergent and sometimes even contradictory. To better elucidate the relationship between altered gut microbiota and IBS, we characterized fecal microbiota of diarrhea-predominant IBS (IBS-D) patients and further explored the effect of rifaximin on gut microbiota using bacterial 16S rRNA gene-targeted pyrosequencing. In our study, IBS-D patients defined by Rome III criteria and age-and-gender matched healthy controls (HC) were enrolled to investigate the fecal microbiota alterations. These IBS-D patients were then treated with rifaximin for 2 weeks and followed up for 10 weeks. Fecal microbiota alterations, small intestine bacterial overgrowth (SIBO) and gastrointestinal (GI) symptoms of IBS-D patients were analyzed before and after treatment. Our results showed fecal microbiota richness but not diversity was decreased in IBS-D patients as compared to HC and there were alterations of fecal microbiota at different taxonomy levels. The abundant phyla Firmicutes was significantly decreased and Bacteroidetes was increased in IBS-D patients. Moreover, the alterations of predominant fermenting bacteria such as Bacteroidales and Clostridiales might be involved in the pathophysiology of IBS-D. In addition, rifaximin was effective in terms of SIBO eradication and even GI symptoms of IBS-D patients achieved at least 10-week improvement after treatment. Furthermore, rifaximin induced alterations of some special bacteria rather than affected the overall composition of microbiota in IBS-D patients. Meanwhile, a potential decrease in propanoate and butanoate metabolism was found in these IBS-D patients after rifaximin treatment. Taken together, there were alterations of gut microbiota in IBS-D patients as compared to HC. Rifaximin could relieve GI symptoms, modify gut microbiota in IBS-D patients and eradicate SIBO in those patients with SIBO, suggesting an additional therapeutic mechanism of rifaximin in the treatment of IBS-D. Our findings of compositional gut microbiota alterations in IBS-D and the effect of rifaximin on the gut microbiota implied that altered gut microbiota were associated with the pathogenesis of IBS.

Duodenal and rectal mucosal microbiota related to small intestinal bacterial overgrowth in diarrhea‐predominant irritable bowel syndrome

“…The microbial richness and diversity increased in duodenal mucosa while decreased in rectal mucosa in SIBO + IBS‐D. In condition of SIBO, bacteria thriving and ectopic colonization resulted in raised microbial diversity in the small intestine, as well as in the duodenum; on the contrary, overgrowth of the dominant strains in the colorectum was speculated to restrain the biological diversity . There were marked changes of both duodenal and rectal mucosal microbiota in SIBO + compared with SIBO − IBS‐D patients, with increased MDI values but completely distinct genera increase or decrease between the duodenum and the rectum.…”

Irritable Bowel Syndrome between Molecular Approach and Clinical Expertise—Searching for Gap Fillers in the Oxidative Stress Way of Thinking

“…On the other hand, no important differences were noted among Bacteroides-Prevotella group, Enterococcus, Escherichia coli, or Clostridium coccoides within these patients. In IBS-D patients, Lactobacillus and Bifidobacterium strains' concentration is lower compared with IBS-C, with the higher prevalence in Chinese subjects [43,44]. A study conducted by using cohorts from Iberian and Scandinavian Peninsula with different ages and diagnosed according to Rome II and III criteria concluded that dysbiosis was detected in 73% of IBS patients, as compared to healthy controls in which dysbiosis was 16% [45].…”

The propionic acid and butyric acid in serum but not in feces are increased in patients with diarrhea-predominant irritable bowel syndrome

“…Irritable Bowel Syndrome (IBS) is one of the most common functional bowel disorders characterised by recurrent or chronic abdominal pain accompanied by changes in bowel habits or associated with bowel movements [1]. It affects 7% to 21% of the population worldwide and 1 to 16% in China [2]. It Short-chain fatty acids (SCFAs) are metabolites formed by gut microbiota from complex dietary carbohydrates.…”