Lower Level of Bacteroides in the Gut Microbiota Is Associated with Inflammatory Bowel Disease: A Meta-Analysis.

Background and Aims. Multiple studies have reported associations between inflammatory bowel disease (IBD) and the flora disequilibrium of Bacteroides. We performed a meta-analysis of the available data to provide a more precise estimate of the association between Bacteroides level in the gut and IBD. Methods. We searched PubMed/MEDLINE, EMBASE, Cochrane Library, Wiley Library, BIOSIS previews, Web of Science, CNKI, and ScienceDirect databases for published literature on IBD and gut microbiota from 1990 to 2016. Quality of all eligible studies was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS). We compared the level of Bacteroides in IBD patients with that in a control group without IBD, different types of IBD patients, and IBD patients with active phase and in remission. Results. We identified 63 articles, 9 of which contained sufficient data for evaluation. The mean level of Bacteroides was significantly lower in Crohn's disease (CD) and ulcerative colitis (UC) patients in active phase than in normal controls. The level of Bacteroides in remission CD and UC patients was much lower than patients in the control group. Bacteroides level was even lower in patients with CD and UC in active phase than in remission. Conclusions. This analysis suggests that lower levels of Bacteroides are associated with IBD, especially in active phase.