7 WORLD GASTROENTEROLOGY NEWS JANUARY 2016 Gastro 2015: AGW-WGO | Expert Point of View | Gastro 2016: EGHS-WGO | WDHD News | WGO & WGOF News | WGO Global Guidelines | Calendar of Events Gut Microbiota, Diet, and Antibiotics in IBD Pathogenesis; from a Developing Country Perspective Tarkan Karakan, MD Gazi University Department of Gastroenterology Ankara, Turkey There is a close relationship between the human host and the intestinal microbiota, which is an assortment of microorganisms protecting the intestine against colonization by ex-ogenous pathogens. Recent advances in culture-independent techniques, including next generation sequencing and metagenomics, have improved our overall understanding of the gut microbiota as well as the importance of its interaction with the mucosal immune system in the pathogenesis of inflammatory bowel disease (IBD) 1. Antibiotics are able to change the microbiota composition in the gut by decreasing microbiome diversity as well as negatively affecting the overall metabolic status of the gut microbi-ome 2. This change is thought to have long-lasting impact on immune toler-ance and sensitivity to pathogens, thus favoring the onset of IBD. Recent literature revealed an increased risk of IBD in adults related to childhood exposure to antibiotics in a dose-de-pendent manner. The exposure to any kind of antibiotics increased the risk of developing Crohn’s disease (CD) (OR 1.7, 95% CI 1.4–2.2), but not ulcerative colitis (UC) 3-5. IBD patients have lower microbial diversity and Firmicutes and Bacte-roidetes phyla 6. Studies profiling the gut microbiota in patients with IBD compared with controls have consis-tently shown changes in microbiota composition as well as reduction in overall biodiversity 7. Disease state is associated with a drop in abundance of several taxa. Faecalibacterum praus-nitizi is decreased in ileal CD and it is increased during recovery phase of UC 8. Other studies showed decreased numbers of adherent-invasive E. coli, Enterobacteria, Fusobacteria, Myco-bacterium avium paratuberculosis, and Clostridium difficile. Moreover, Bacteroides, Clostridia, Bifidobacteria, and Ruminococcaceae are increased in IBD patients. Metagenomic studies revealed more stability of functional-ity than microbiota at phylogenetic level 9. One study identified only nine bacterial classes associated with UC patients compared with controls, but 21 differences in functional and meta-bolic pathways, with similar findings for CD patients 10. Gut microbiota in IBD is also shows spatial variations from proximal to distal parts. By sys-tematically sampling both mucosa and lumen associated microbiota, Lavella et al found significant differences in both UC and control patients. Few studies investigated the role of fungal signatures in IBD patients. Two decades ago, S. cerevisia mannan (ASCA) was found in the sera of CD patients. Fungi and C. albicans are particularly profound in CD patients, as in first-degree healthy relatives of them. Pediatric IBD is associated with reduced diversity in both fungal and bacterial gut microbiota. Specific Can-dida taxa were found to be increased in abundance in the IBD samples 11. Microbiota also has a predictive val-ue for disease recurrence in IBD. Pres-ence of R. gnavus, B. vulgatus, and C. perfringens and absence of Blautia and Roseburia in fecal samples of patients with UC before surgery is associated with a higher risk of pouchitis 12. Early endoscopic Crohn’s recurrence was associated with high counts of E. coli, Bacteroides, and Fusobacteria. A lower proportion of F. prausnitzii on resected ileal Crohn’s mucosa was as-sociated with endoscopic recurrence at six months (P = 0.03), suggesting that there may be a microbial signature, detectable at the time of resection, that can inform disease behavior, and the risk of recurrence postoperatively. The role of diet in shaping the gut microbiota is widely recognized, and several recent reviews provide a com-prehensive treatment of the subject. Microbiota is modulated through diet and nutritional habits even if, as the composition of gut microbiota seems to be rather stable over long periods of adulthood, its richness may be individually different. Reduced richness of gut microbiota has been found in patients with IBD. However, until recently, not many studies have broadly and systematically considered the association between habitual diet and gut microbiota. Some popula-tions eat differently because they have different access to foods, and this can determine significant differences in the taxonomic composition of their gut microbiota, distinguishing agrarian and Western diets. Specific compositional patterns of the gut microbiota have also been associated with habitual diet, clearly linking dif-
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