Alterations in the tongue coating microbiome in patients with diarrhea-predominant irritable bowel syndrome: a cross-sectional study

Background: The gut microbiota plays a critical role in the occurrence and development of irritable bowel syndrome with predominant diarrhea (IBS-D), however, IBS-D-associated tongue coating microbiome dysbiosis has not yet been clearly defined.Methods: The structure and composition of tongue coating microbiome were analyzed in 23 IBS-D patients and 12 healthy controls using 16S rDNA high-throughput sequencing analysis.Results: The 16S rRNA sequencing results revealed that the overall observed OTUs of tongue coating microbiome in IBS-D patients exhibited a significant decrease compared with the healthy controls. Alpha diversity analysis showed that the diversity and community richness were significantly reduced in IBS-D patients, and PCoA revealed a distinct clustering of tongue coating microbiome between the IBS-D patients and healthy controls. Microbial comparisons at the genus level showed that the abundance of Veillonella, Prevotella, in IBS-D patients were higher than those in healthy controls, while Streptococcus, Haemophilus, Granulicatella, and Rothia, were significantly reduced compared with the healthy volunteers. Functional analysis results showed significant differences in 88 gene functional metabolic pathways between the IBS-D patients and the healthy controls, including fatty acid biosynthesis.Conclusion: These findings identified the structure, composition, functionality of tongue coating microbiome in IBS-D patients, and hold promise the potential for biomarkers and therapeutic targets during IBS-D management.