Determination of the discriminant score of intestinal microbiota as a biomarker of disease activity in patients with ulcerative colitis

BACKGROUND: In recent years, the gut microbiota has been found to provide an important link to the development of inflammatory bowel diseases (IBD) like ulcerative colitis (UC). Accordingly, inter-individual variation in the gut microbial community may be linked to inter-individual variation in the risk of IBD or other diseases. Further, the Terminal Restriction Fragment Length Polymorphism (T-RFLP) is a molecular biology technique for profiling bacterial species in faecal samples. This study was to evaluate a biomarker based on intestinal microbiota. METHODS: The study subjects were 69 patients with UC together with 80 relatives as controls. Twenty-three patients had active UC (group I) and 46 had quiescent UC (group II). The later included 17 patients with mild inflammation in the large intestine (group IIa), 29 without inflammation (group IIb). The patients’ relatives were consanguineous (group III, n = 47), and non-consanguineous (group IV, n = 33). Faecal samples were obtained from all subjects for the investigation of intestinal microbiota by applying the T-RFLP method. The Discriminant analysis of operational-taxonomic-unit (OTU) on T-RFLP fingerprints was performed. The Canonical Discriminant Function Coefficient (Df) for each OTU was calculated. The individual OTUs were multiplied by the Df value, and the sum was termed the Discriminant Score (Ds). RESULTS: The Ds decreased thus: group I > group IIa > group IIb > group III > group IV. Significant difference was calculated for group I vs group IV (P < 0.01), group I vs group IIb (P < 0.05), group I vs group III (P < 0.01), group IIa vs IV (P < 0.01), group IIb vs group IV (P < 0.01), group III vs group IV (P < 0.01), indicating a strong association between gut microbial species and the development of UC. CONCLUSIONS: In this study, the Ds related to UC, or otherwise absence of UC in the five groups. Potentially, Ds may become a clinically relevant biomarker of disease activity in UC. To our knowledge, this is the first application of the Ds to the study of microbiota in UC patients, consanguineous and non-consanguineous relatives. TRIAL REGISTRATION: Clinical trial No: UMIN 000004123.