Gut Microbiota In Diarrhea Predominant Irritable Bowel Syndrom Patients

Background and objectsIrritable bowel syndrome (IBS) is a functional gastrointestinal disease characterized by abdominal pain, bloating, altered bowel habits and altered fecal consistency. According to the symptoms, IBS were further classified as diarrhea predominant IBS (IBS-D), constipation predominant IBS (IBS-C), mixed IBS (IBS-M) and unsubtyped IBS1. The etiology is still not completely clear yet, altered gut microbiota plays an important role in the pathogenesis of IBS. We aimed to investigate the differences of gut microbiota between diarrhea predominant irritable bowel syndrome (IBS-D) patients and healthy controls by Miseq high-throughput sequence and Quantitative real time PCR (QPCR). Evaluate correlation between severity of symptoms, life of quality and quantity of specific gut bacteria.Methods40 IBS-D patients who met Rome III criteria and 20 healthy controls were recruited in this study. The patients were asked to fill out questionnaires about IBS symptoms and SF-36 quality of life scales.16S rDNA were extracted from stools of healthy controls and IBS patients, randomly pick up 3 samples each for high-throughput sequence, then to testify its results by QPCR with more samples. Evaluate correlation between severity of symptoms, life of quality and quantity of specific gut bacteria.Results:1) The intestinal microbiota of IBS-D patients differed significantly from that of controls. High throughput sequence shows that fecal bacteria in IBS-D patients is mainly composed by Prevotella (69.06%) whereas in healthy controls is Bacteroides (60.62%).2) The microbiota of IBS-D patients, compared with controls, increased number of E coli (P<0.01) and decreased numbers of Bifidobacteria and Lactobacillus (P<0.05) were observed. The most strikingly, Prevotella is over 100-fold in IBS-D than in healthy controls.3) The quantity of Prevotella, Bacteroides, Bifidobacteria Lactobacillus and E coli showed no correlation with severity of symptoms and quality of life of patients.ConclusionIncreased Prevotella abundance appears in IBS patients, Prevotella might play an important role in the mechanism of IBS.PART II Establishment of a mouse model of post-infectious irritable bowel syndrome and analysis of gut microbiotaBackground and objectsThe symptoms of part of IBS patients initiated after acute intestinal infection, the term post-infectious irritable bowel (PI-IBS) was presented. We use Trichinella spiralis infection mouse model to analyze their gut microbiota by QPCR to further testify the role of gut microbiota in the pathogenesis of IBS.MethodsEstablish a mouse model of post-infectious irritable bowel syndrome, evaluate visceral hypersensitivity and intestinal inflammation, investigate gut microbiota of this model and compare the differences with healthy controls.ResultsPI-IBS mouse expressed higher visceral hyperactivity. The abundance of fecal Prevotella was significantly increased with about 3 fold change in PI-IBS mice when compared with control groups (p<0.05). Bacteroides, E. coli., Bifidobacteria and Lactobacillus showed no statistical differences between PI-IBS and control mice.ConclusionPrevotella increased in PI-IBS mice while others showed no differences, it might play a critical role in the pathogenesis of IBS.