• Zuojing Liu, Shiwei Zhu, Meibo He, Mo Li, Hui Wei, Lu Zhang, Qinghua Sun, Qiong Jia, Nan Hu, Yuan Fang, Lijin Song, Chen Zhou, Heqing Tao, John Y Kao, Huaiqiu Zhu, Chung Owyang, and Liping Duan.
• Department of Gastroenterology, Peking University Third Hospital, Haidian District, Beijing 100191, China.
• Chin. Med. J. 2022 Jul 20; 135 (14): 171617271716-1727.

BackgroundAs a non-invasive and effective diagnostic method for small intestinal bacterial overgrowth (SIBO), wild-use of breath test (BT) has demonstrated a high comorbidity rate in patients with diarrhea-predominant irritable bowel syndrome (IBS-D) and SIBO. Patients overlapping with SIBO respond better to rifaximin therapy than those with IBS-D only. Gut microbiota plays a critical role in both of these two diseases. We aimed to determine the microbial difference between IBS-D overlapping with/without SIBO, and to study the underlying mechanism of its sensitivity to rifaximin.MethodsPatients with IBS-D were categorized as BT-negative (IBSN) and BT-positive (IBSP). Healthy volunteers (BT-negative) were enrolled as healthy control. The patients were clinically evaluated before and after rifaximin treatment (0.4 g bid, 4 weeks). Blood, intestine, and stool samples were collected for cytokine assessment and gut microbial analyses.ResultsClinical complaints and microbial abundance were significantly higher in IBSP than in IBSN. In contrast, severe systemic inflammation and more active bacterial invasion function that were associated with enrichment of opportunistic pathogens were seen in IBSN. The symptoms of IBSP patients were relieved in different degrees after therapy, but the symptoms of IBSN rarely changed. We also found that the presence of IBSN-enriched genera ( Enterobacter and Enterococcus ) are unaffected by rifaximin therapy.ConclusionsIBS-D patients overlapping with SIBO showed noticeably different fecal microbial composition and function compared with IBS-D only. The better response to rifaximin in those comorbid patients might associate with their different gut microbiota, which suggests that BT is necessary before IBS-D diagnosis and use of rifaximin.RegistrationChinese Clinical Trial Registry, ChiCTR1800017911.Copyright © 2022 The Chinese Medical Association, produced by Wolters Kluwer, Inc. under the CC-BY-NC-ND license.

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