Changes in oral flora of patients with functional dyspepsia.

To explore the changes in oral flora in people with functional dyspepsia (FD). Unstimulated saliva was collected from 21 FD patients diagnosed according to the Rome IV criteria and from 12 healthy controls (HCs) for 16SrRNA sequencing. The pH of saliva samples and community periodontal index (CPI) were tested. The prevalence of small intestinal bacterial overgrowth (SIBO) was obtained by the methane-and hydrogen-based breath test. At the phylum level, FD patients had a higher relative abundance of Spirochaetes and a lower relative abundance of Fusobacteria, TM7 and Proteobacteria than HCs (p < 0.01). In the saliva, Kingella and Abiotrophia genus levels showed significant changes between the FD and HC groups (p < 0.01). Salivary species level marker Intermedia was significantly different between FD and HC groups (p < 0.01). The oral pH of FD patients was higher than that of HCs (p < 0.01). The mean CPI of the FD group was 1.52 and that of the HC group was 0.17 (p < 0.01). Moreover, 71.4% of the FD group was positive for SIBO. The oral flora of FD patients was different from that of HCs. Spirochaetes, Kingella, Abiotrophia, and Intermedia may be diagnostic indicators of FD.