P673. Determination of the discriminant score of intestinal microbiota as a biomarker of disease activity in patients with ulcerative colitis
K. Fukuda, Y. Fujita, St Luke's International Hospital, Department of Gastroenterology, Tokyo, Japan
The gut microbiota has been recognized as an essential factor in ulcerative colitis (UC). Further, the Terminal Restriction Fragment Length Polymorphism (T-RFLP) is a molecular biology technique for profiling microbial communities based on the position of a restricted site closest to a labeled end of an amplified gene. T-RFLP is an established technique for analysing bacterial species in faecal samples.
This was a quantitative analysis with a major focus on evaluating a biomarker based on intestinal microbiota. The subjects were 69 UC patients together with an 80 relatives as controls. Twenty-three patients had active UC (group I) and 46 had quiescent UC (group II). The latter included 17 with mild inflammation in the large intestine (group IIa), and 29 without inflammation (group IIb). The patients' relatives were consanguineous (group III, n = 47), and non-consanguineous (group IV, n = 33). The Discriminant analysis of operational-taxonomic-unit (OTU) on T-RFLP fingerprints was done. The Canonical Discriminant Function Coefficient (Df) for each OTU was calculated by using group I and group IV, in whom the difference of intestinal flora was thought to be greatest. The individual OTUs were multiplied by the Df value, and the sum was termed the Discriminant Score (Ds). The analyses was by SPSS (IBM Statistics 20.0).
The Ds decreased thus: group I > group IIa > group IIb > group III > group IV. As certain strains of bacteria are associated with the development of UC, while others not, this should show up in the OTU values in T-RFLP analysis. The analysis was set to factor this assumption, and the OUTs with 0 value ≥95% of all cases together with the OTUs of structure matrix value <0.01 according to the Discriminant analysis were excluded. 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. group IV (P < 0.01), group IIb vs. group IV (P < 0.01), group III vs. group IV (P < 0.01).
In this study, the Ds related to UC activity, 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.