Detection of enterotoxigenic Bacteroides fragilis in patients with ulcerative colitis

PURPOSE Ulcerative colitis (UC) as a type of inflammatory bowel disease (IBD), presumed to occur as a consequence of increased immune responses to intestinal microbiota in genetically susceptible individuals. Enterotoxigenic Bacteroides fragilis (ETBF) strains are important intestinal bacteria that can be involved in IBD. The aim of this study was to design a quantitative assay for detection of B. fragilis and ETBF and also to find their association with UC. METHODS Ninety-five biopsies were collected from patients with UC (n = 35) and with no IBD (nIBD, n = 60). All the specimens were cultured in Bacteroides bile esculin agar medium. Specific primers and probes were designed for quantitative real-time PCR (QRT-PCR) based on 16S rRNA and bft genes sequences of ETBF. RESULTS The bft genes were detected in 51.4% of UC samples and 1.6% of nIBD samples, respectively. In UC patients, 37.1% of samples with diarrhea and 11.4% of samples without diarrhea, harbored the bft gene. Mean value of the number of ETBF with bft gene in UC and nIBD samples were 4.46 ן 102 and 1.96, respectively. Likewise these result for 16S rRNA gene in UC and nIBD samples were 2.0 × 103 and 8.4 × 103, respectively. CONCLUSIONS There was no significant association between presence and numbers of 16S rRNA gene of B. fragilis and UC. ETBF was detected more in UC specimens and biopsies of UC patients with diarrhea than in the control group. These data demonstrated that ETBF is associated with development of UC and as a causative agent for the development of diarrhea in these patients.