Mucosa-Associated Microbial Profile Is Altered in Small Intestinal Bacterial Overgrowth

Abstract

The overall gut microbial profile of patients with small intestinal bacterial overgrowth (SIBO) has not been thoroughly investigated. We investigated the microbial communities of mucosal specimens from the duodenum, ileum, sigmoid colon, and feces of patients with and without SIBO, as diagnosed by lactulose breath testing. The bacteria present in the mucosal and fecal samples were identified using 16S rRNA gene sequencing. Further analysis was performed using the linear discriminant analysis (LDA) effect size method, random forest analysis, and receiver operating characteristic analysis. The microbial diversities of the fecal samples were significantly lower than those of the mucosal samples from the duodenum, ileum, and sigmoid colon (P < 0.001, P < 0.001, and P < 0.001, respectively), while the bacterial compositions of the ileac mucosal samples and sigmoid mucosal samples were similar. The bacterial composition of either the fecal or duodenal mucosal samples were significantly different from those of the other three groups (ANOSIM R = 0.305, P = 0.001). The bacterial compositions of the mucosal samples of the duodenum, ileum, and sigmoid colon in the SIBO + subjects were significantly different from those of the SIBO− subjects (ANOSIM P = 0.039, 0.002, and 0.007, respectively). The relative abundances of 7, 18, and 8 genera were significantly different (LDA score > 3) in the mucosal samples of the duodenum, ileum, and sigmoid colon between the SIBO + and SIBO− groups. Four genera (Lactobacillus, Prevotella_1, Dialister, and norank_f__Ruminococcaceae) showed similar changes among the mucosal samples of the duodenum, ileum, and sigmoid colon in the SIBO + subjects. A signature consisting of four genera in the duodenal mucosa, three genera in the ileac mucosa, or six genera in the mucosa of the sigmoid colon exhibited predictive power for SIBO (area under the curve = 0.9, 0.93, and 0.87, respectively). This study provides a comprehensive profile of the gut microbiota in patients with SIBO. Dysbiosis was observed in the mucosa-associated gut microbiome but not in the fecal microbiome of patients with SIBO. Furthermore, we identified mucosa-associated taxa that may be potential biomarkers or therapeutic targets of SIBO. Further investigation is needed on their mechanisms and roles in SIBO.

The small intestine: dining table of host–microbiota meetings

“…However, the efforts in characterizing the small intestinal ecology in SIBO patients may result in diverging results due to the difference in sampling locations across different study cohorts (Leite et al 2020a , Li et al 2021 ) (Table 7 ). Additionally, inconsistencies among SIBO studies might also be related to the type of SIBO, often not indicated.…”

Risk factors for small intestinal bacterial overgrowth in patients with acute ischaemic stroke

“…According to a recent study, mucosal microbial compositions were significantly different, and microbial richness values were dramatically lower in the ileac of SIBO-positive participants than in those negative for SIBO. This suggests that SIBO may be an indicator of intestinal flora dysbiosis [27]. Therefore, we explored the occurrence of such dysbiosis in patients with AIS by assessing SIBO.…”

Alterations of ileal mucosa-associated microbiota in hypercholesterolemia patients

“…After bowel preparation with oral polyglycol powder, colonoscopy was performed for each subject to take a biopsy of the terminal ileum, 5–10 cm from the ileocecal valve as described in previous studies [ 9 , 22 ]. The biopsy was taken during insertion, not exit, of the colonoscopy to minimize contamination of the proximal intestine by microbiota.…”

“…As described in previous studies [ 9 ], the V3–V4 hypervariable region of the 16S rRNA bacterial gene was amplified by PCR using Primers 338F (5′-ACTCCTACGGGAGGCAGCAG-3′) and 806R (5′-GGACTACHVGGGTWTCTAAT-3′). A total of three amplification replicates with a volume of 20 μl were obtained for each sample, and all PCR products from these three replicates were aggregated, as well as purified and quantified using the AxyPrep DNA Gel Extraction Kit (Axygen, USA) and a Quantus™ Fluorometer (Promega, USA), respectively.…”

“…The gut microbiota plays a variety of roles on the host, including protection against potential pathogens, initiation and training of the immune system, providing nutrition to the epithelium, maintaining the mucosal barrier function, and extracting energy from the diet [ [5] , [6] , [7] ]. However, it is also a possible contributor to numerous human disorders [ 8 , 9 ]. In addition to Crohn's disease and ulcerative colitis, a growing number of studies have linked the gut microbiota to certain metabolic disorders, such as atherosclerosis [ 2 ], obesity [ 10 ], type 2 diabetes mellitus [ 11 ], and non-alcoholic fatty liver disease (NAFLD) [ 12 ].…”