Background and aims: The pathogenesis of primary biliary cholangitis (PBC) is associated with alterations of gut microbiota. We compared the gut microbiota of PBC patients and healthy controls from Zhejiang province, and assessed the use of gut microbiota composition as a tool for diagnosis of PBC. Methods First, 16S rRNA gene sequencing was used to characterize the gut microbiota of patients with treatment-naive PBC (n = 25) and matched healthy controls (n = 25). Then, the use of gut

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... composition for the diagnosis of PBC and as an indicator of PBC severity was determined. Results The gut microbiota of PBC patients had lower in three metric of alpha-diversity (ace, Chao1, and observed features) and fewer overall number of genera (all p < 0.01). PBC patients had significantly enrichment of 4 gut genera and significant depletion of 8 gut genera. We identified 6 amplicon sequence variants (Serratia, Oscillospirales, Ruminococcaceae, Faecalibacterium, Sutterellaceae, and Coprococcus) as optimal biomarkers to distinguish PBC patients from controls, based on receiver operating characteristic analysis which indicated the area under the curve was 0.824. PBC patients who were anti-gp210-positive had lower levels of Oscillospiraceae than those who were anti-gp210-negative. KEGG functional annotation suggested the major changes in the gut microbiota of PBC patients were related to lipid metabolism and biosynthesis of secondary metabolites. Conclusion We characterized the gut microbiota of treatment-naive PBC patients from Zhejiang province. These patients had significant alterations in their gut microbiota, suggesting a potential use of gut microbiota as a non-invasive tool for the diagnosis of PBC.