IDDF2023-ABS-0089 Shifts of gut microbiota in fecal microbiota transplantation for ulcerative colitis detected by a novel absolute abundance quantitative method

BackgroundHigh-throughput sequencing has been widely used in characterizing microbial communities and revealing microbial-host interactions. However, the abundance produced by this technique is semi-quantitative, leading researchers to focus on the relative abundance of microbes and ignore the total microbial load. Moreover, changes in relative abundance do not accurately reflect the actual shifts in microbial load, which may hinder further microbiological research.MethodsIn this study, a bacterial absolute abundance quantitative method based on high-throughput 16S rRNA gene V4 sequencing was developed and used to reveal the changes in the gut microbiota of patients with ulcerative colitis (UC) who underwent fecal microbiota transplantation (FMT) (IDDF2023-ABS-0089 Figure 1 (a) Design and workflow of spike-in bacterium DNA). Samples were collected and analyzed before FMT (W0) and at 1 (W1), 4(W4) and 12 (W12) weeks after FMT.ResultsThe spike-in bacterium Bacillus baekryungensis 700Cs for absolute abundance analysis was well distinguishable from the gut bacteria and did not affect the bacterial composition of fecal samples. The overall bacterial communities changed significantly (P