The Mucosa Associated Microbiota Of Small Bowel In Patients With Crohn’s Disease

Background and AimCrohn’s disease (CD) is a chronic, lifelong, relapsing disease whose causes and mechanisms have not been totally clear yet, mainly affecting the gastrointestinal tract. CD and ulcerative colitis (UC) are the two main components of inflammatory bowel disease (IBD), which is one of the main health troubles in western countries. With the development of economy and the improvement of life quality, the incidence and prevalence of CD in Asia-Pacific area have increased sharply to date. There is a general agreement that variations in the patient’s genetic information, changes in the surrounding environment, alterations in the composition of the gut microbiota and the abnormal reactivity of the intestinal mucosal immune response are at the foundation of IBD pathogenesis. The interaction between intestinal mucosa and microbiota is drawing great interest currently. However, most of the former researcheres focused on the intestinal microbiota using fecal, colonic or terminal ileum samples. We still know little about the small intestinal mucosa associated microbiota, especially in CD patients.Now that we have single balloon enteroscopy (SBE) to reach the jejunum and proximal ileum to examine the inflammatory mucosa, we carried out this study. Our aim is to investigate the longitudinal distribution of the mucosa associated microbiota as well as the difference between segments with and without inflammation in patients with CD; to reveal the difference of the microbial composition between CD patients and non-IBD patients; to study the relationship between alteration of the microbiota and the activity and severity of CD.MethodsPatients who took single balloon enteroscopy were enrolled in this study from November 2014 to October 2015 in our hospital. They were divided into experiment group and control group separately. The former consisted of patients with CD and the latter non-IBD patients, including healthy individuals. Biopsies were taken from the small intestine and put in the liquid nitrogen immediately then kept under -80℃. The microbial information was obtained after PCR and high-throughput sequencing on Illumina MiSeq platform.ResultsThere were eight members, nineteen samples (out of twenty five patients, one hundred and fifty two samples in total) finally got sequenced, five in experiment group and three in control group. The abundance and diversity both decreased at the inflammatory region. The dominant phylum in all samples was Firmicutes, followed by Proteobacteria, Bacteroidetes and Actinobacteria in experiment group, while in control group by Bacteroidetes Proteobacteria, and Actinobacteria, which was similar to the former research. On the genus level, Bacillus, Enterococcus, Lactococcus, Alkaliphilus, Enterobacteriaceae, Raoultella, Oceanobacillus, Paenibacillus, Bacteroides dominated the experiment group; while the most microbiomes in control group were Lachnospiraceae_NK4A136_group, Bacillus, Bacteroidales_S24-7_group_norank, Enterococcus, Lachnospiraceae unclassified, Lactococcus, etc. Compared to control group, an obvious increase of Bacillus, Lactococcus, Enterococcus and a decrease of Clostridiales, Lachnospiraceae, Bacteroides could be observed in experiment group. Faecalibacterium prausnitzii was not seen maybe due to low concentration.Conclusions1. The CD patients had an obvious drop in the abundance and diversity when comes to the non-IBD patients;2. The portion of Proteobacteria increased while Bacteroidetes decreased in CD patients, which was different from non-IBD patients.3. There was microbial dysbiosis in the small bowel of CD patients definitely with an increased portion of Bacillus, Lactococcus and Enterococcus while a decrease portion of Clostridiales, Lachnospiraceae and Bacteroides.4. The abundance and diversity didn’t decrease much in inflammatory mucosa.SignificanceWe obtained precious small intestinal mucosal tissues with the help of single balloon enteroscopy for the first time and studied the relationship between the small bowel mucosa associated microbiota and Crohn’s disease.