Supragingival Plaque Microbiome Composition Associated with Oral Lichen Planus Activity and Desquamative Gingivitis Severity: An Exploratory, Cross-Sectional, Shotgun Metagenomic Study

Abstract The microbial contribution to desquamative gingivitis (DG), a frequent and debilitating form of immune-mediated oral lichen planus (OLP), remains undefined. This study employed shotgun metagenomic sequencing to investigate the role of the oral microbiome in DG site involvement and severity, as well as OLP disease activity. In this exploratory, cross-sectional study, supragingival plaque samples were collected from nine OLP patients at desquamative gingivitis-affected sites (DG sites), sites not affected by desquamative gingivitis (non-DG sites), and pooled full-mouth samples. Shotgun metagenomic sequencing was performed to reveal oral microbial profiles and their functional pathways. Disease severity was assessed using the Oral Lichen Planus Disease Activity Scale (OLP-DAS) and the Desquamative Gingivitis Clinical Score (DGCS). Associations between microbial profiles and disease severity were assessed using Spearman's correlation. Microbial and functional pathway profiles were compared between DG and non-DG sites using the paired Wilcoxon signed-rank test. A p-value <0.05 was considered statistically significant. Significant differences in microbial composition between DG and non-DG sites were identified, including 6 genera and 17 species (p < 0.05). Several taxa showed notable correlations with disease severity (r ≥ 0.7), according to DGCS, with 10 genera and 16 species positively associated with DGCS, and 5 genera and 8 species associated with OLP-DAS. Notably, the fructan biosynthesis pathway showed a significant inverse correlation with DG severity (r = − 0.70, p < 0.05) and was linked to Actinomyces sp. oral taxon 448, which was enriched in DG sites. This suggested that increasing disease severity may be associated with reduced microbial polysaccharide-production potential. The DG microbiome shows distinct functional and taxonomic changes. Fructan biosynthesis was more abundant in DG sites than in non-DG sites, but showed an inverse correlation with DG severity, highlighting candidate biomarkers and potential therapeutic targets.