Alterations of Gastric Fluid Microbiota in Functional Dyspepsia and Its Subtypes Including Postprandial Distress Syndrome and Epigastric Pain Syndrome: A Pilot Study

Background/Aims: Evidence suggests that dysbiosis is potentially associated with the pathophysiology of functional dyspepsia (FD).As a pilot study, this study aims to explore alterations of gastric fluid microbiota in FD and the potential differences in gastric microbiota between postprandial distress syndrome (PDS) and epigastric pain syndrome (EPS), with a limited sample size, compared with healthy controls.Methods: Eighteen Korean patients with FD and 14 healthy controls were enrolled in the study.Gastric fluid was collected using a sterilized tube inserted through the working channel of the endoscope.DNA was extracted from the fluid samples and 16S rRNA sequencing was performed using the MiSeq™ platform.Samples from 11 patients with FD and 6 healthy controls were included in the final analysis.Results: The Chao1 and Shannon indices did not differ significantly between the FD, PDS, or EPS groups and the control group.No significant differences in beta diversity were observed at the phylum level between the FD and control groups.Significant differences in beta diversity were observed at the genus level in the FD, PDS, and EPS groups, compared to the control group.At the genus level, Centipeda was differentially associated with the FD and PDS groups, while Collinsella, Holdemanella, and Paraprevotella were differentially associated with the EPS group.Species associated with the PDS group differed from those associated with the EPS group.Conclusions: The microbiota composition of gastric fluid appears to be altered in patients with FD, compared with healthy controls.Potential differences in gastric microbial composition exist between the PDS and EPS subtypes, requiring additional research to elucidate the mechanistic roles of those microbes.