Small intestinal bacterial overgrowth is associated with Diarrhea-predominant irritable bowel syndrome by increasing mainly Prevotella abundance

Abstract

Objective: Diarrhea-predominant irritable bowel syndrome (IBS-D) is the main subtype of IBS, a chronic functional gastrointestinal disorder. Small intestinal bacterial overgrowth (SIBO), which is characterized by dysbiosis of the bowel, causes gastrointestinal symptoms quite similar to IBS-D. However, whether SIBO correlates with IBS-D and its further mechanism remain unknown.

Materials and Methods: The study included 60 IBS-D patients that fulfilled Rome IV criteria and 60 healthy controls. All subjects were undergoing a lactose breath test (LBT) to diagnose SIBO. IBS-D patients were further assigned to negative SIBO (SIBO^-) subgroup and positive SIBO (SIBO⁺) subgroup to analyze the scores of symptoms and differences in the fecal microbiota.

Results: The prevalence of SIBO in IBS-D patients was higher than that in healthy controls (51.7% vs. 16.7%, p ≤ .001). In addition, IBS-SSS in SIBO⁺ subgroup was significantly higher than SIBO^- subgroup (p = .015). The 16S rRNA analyses showed that composition and abundance of fecal microbiota were obviously different between the two subgroups. There was a remarkable increase in Prevotella in IBS-D patients, especially in IBS-D SIBO⁺ sufferers. Meanwhile, there were a moderately positive correlation of the abundance of Prevotella (rho = 0.458, p ≤ .001) with IBS-SSS.

Conclusion: SIBO is associated with IBS-D, which may be related to alteration in the intestinal microbiota. These findings suggest the potent role of Prevotella in gastrointestinal symptoms between SIBO and IBS-D, thus provide a novel insight into the connection between SIBO and IBS-D.

Keywords:

• Small intestinal bacterial overgrowth
• Diarrhea-predominant irritable bowel syndrome
• intestinal microbiota
• Prevotella

Disclosure statement

All authors declare that there is no conflict of interest.

Additional information

Funding

This work was supported by the Science and Technology Innovation Project, the Military Scientific Committee of the People’s Liberation Army of China [Grant number 17-163-12-ZT-002-060-01], Medical Science and Technology Pilot Project for Youth Investigators, the Military Scientific Committee of the People’s Liberation Army of China [16QNP098], Funds for Clinical Medical Research, the Daping Hospital and Research Institute of Surgery Clinical Research affiliated to the Third Military Medical University [2014YLC05] and Chongqing Science and Technology Commission [cstc2015shmszx120047].