Gut oralisation signatures in Parkinson's disease: an integrative multi-study analysis.

Background: Parkinson's disease (PD) compromises oral hygiene and oral health, potentially increasing oral bacterial input to the gut. Whether PD is associated with reproducible faecal enrichment of oral disease-linked taxa remains unclear. Objective: To determine whether oral disease-linked taxa are enriched in the faecal microbiota of individuals with PD. Methods: We conducted a pooled re-analysis of 23 faecal 16S rRNA datasets, comprising 3,594 PD and control samples. eHOMD was used to resolve oral-associated taxa, including caries/endodontic- and periodontitis-linked taxa. SILVA-based profiles were used to assess community diversity and ordination patterns. Differential-abundance analyses accounted for variation between studies. Results: PD samples showed heterogeneous but reproducible enrichment of oral disease-linked taxa, with a prominent caries/endodontic-associated component. The cariogenic-enriched subgroup showed reduced evenness and increased representation of oral taxa including Conclusions: This pooled re-analysis identifies a gut oralization-associated signal in a subset of individuals with PD. Faecal enrichment of oral-associated taxa may represent one component of gut microbiome heterogeneity and may indirectly reflect variation in oral ecosystem status, supporting oral health assessment in future PD microbiome studies.