BACKGROUND AND AIMS The mucosa-associated microbiota (MAM) is not as frequently studied in diarrhea-predominant irritable bowel syndrome (IBS-D) compared to the fecal microbiota. Here, we examined the MAM in the terminal ileum and its correlation with bowel symptoms in IBS-D. METHODS Mucosal biopsies of the terminal ileum from 25 IBS-D patients and 25 healthy controls (HCs) were collected for 16S ribosomal RNA (rRNA) gene sequencing. Correlation analysis was performed. RESULTS Compared to HCs, the MAM in the terminal ileum showed a decreased alpha-diversity in the IBS-D cohort (Chao1 and Shannon indexes, P < 0.05). And the overall MAM profile clustered separately in two groups (ADONIS, P < 0.05). At the phylum level, the relative abundance of Proteobacteria was significantly higher in the ileal MAM of patients with IBS-D while that of Firmicutes was significantly lower. At the genus level, the relative abundance of Pseudomonas was significantly higher in the IBS-D cohort, with lower Bacteroides and Ruminococcus. Moreover, 40.0% of IBS-D patients had multiple small nodules (nodular lymphoid hyperplasia, NLH) on the mucosal surface of the terminal ileum, which indicated a low-grade inflammation. In the IBS-D patients with NLH, the changes of Pseudomonas and Bacteroides were more overt. Correlation analysis revealed that the relative abundance of Pseudomonas positively correlated with abdominal pain and the severity of IBS. CONCLUSION IBS-D patients showed a dysbiosis of MAM in the terminal ileum, which may be associated with bowel symptoms. Moreover, 40.0% of them displayed mucosal low-grade inflammation, with a more severe mucosal microbial disturbance.

中文翻译：

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回肠末端粘膜相关微生物群失调与腹泻为主的肠易激综合征的肠道症状相关。

背景和目的 与粪便微生物群相比，在腹泻型肠易激综合征 (IBS-D) 中，粘膜相关微生物群 (MAM) 的研究并不频繁。在这里，我们检查了回肠末端的 MAM 及其与 IBS-D 肠道症状的相关性。方法 收集 25 名 IBS-D 患者和 25 名健康对照 (HC) 的回肠末端粘膜活检样本，进行 16S 核糖体 RNA (rRNA) 基因测序。进行相关分析。结果 与 HC 相比，IBS-D 队列中回肠末端的 MAM 显示 α 多样性降低（Chao1 和 Shannon 指数，P < 0.05）。总体 MAM 概况分别聚类为两组 (ADONIS, P < 0.05)。在门水平上，IBS-D患者回肠MAM中变形菌门的相对丰度显着较高，而厚壁菌门的相对丰度显着较低。在属水平上，IBS-D 队列中假单胞菌的相对丰度显着较高，拟杆菌和瘤胃球菌的相对丰度较低。此外，40.0%的IBS-D患者回肠末端黏膜表面存在多个小结节（结节性淋巴样增生，NLH），提示存在低度炎症。在伴有NLH的IBS-D患者中，假单胞菌和拟杆菌的变化更为明显。相关分析显示，假单胞菌的相对丰度与腹痛和IBS严重程度呈正相关。结论 IBS-D 患者回肠末端 MAM 失调，这可能与肠道症状有关。此外，其中40.0%表现出粘膜低度炎症，粘膜微生物紊乱更为严重。