Bacteroides, Metabolites, and Lymphocytes: A Triad of Biomarkers in Small Intestinal Bacterial Overgrowth

The purpose of this study was to investigate the clinical characteristics of small intestinal bacterial overgrowth (SIBO) and analyze its relationship with changes in intestinal microbiota and metabolites. The study included patients from Beijing Shijitan Hospital (Feb 2021-Nov 2023) who underwent hydrogen-methane breath tests, hematological tests, and completed questionnaires. Baseline characteristics of SIBO patients were analyzed using descriptive statistics and independent t-tests. Logistic regression and Receiver Operating Characteristic (ROC) curve analysis identified potential SIBO predictors. Chi-square tests assessed the association between SIBO and symptoms. Stool samples from 29 patients underwent 16S rRNA sequencing to analyze gut microbiota and metabolites. Then we explored links between microbiota, metabolites, symptoms, and serum markers. 405 persons in all completed the hydrogen methane breath test, of whom 109 (26.91%) were in the SIBO- and 296 (73.09%) were in the SIBO+. No significant differences were observed between the SIBO+ and SIBO- groups in terms of gender, age, or BMI. However, lymphocyte counts were significantly different between the groups, with lymphocyte count proving to be a better predictor of SIBO in middle-aged and elderly non-obese men. SIBO was significantly associated with diarrhea and acid reflux symptoms. 16S rRNA sequencing of stool samples from 29 patients revealed that Bacteroides was the predominant intestinal microbiota in SIBO patients. Metabolic pathways involving various metabolites were identified as significantly altered in these patients. Additionally, there were significant correlations between various intestinal flora and metabolites with serum markers.