Taxon-specific oral mycobiome differences and bacterial–fungal associations in kidney transplant recipients and donors

Abstract Aims This study characterised the pre-transplant salivary mycobiome of kidney transplant recipients and living donors and investigated cross-kingdom associations with the bacteriome. Methods and Results Mycobiome profiling was performed using ITS sequencing of donor and recipient samples, while paired bacteriome data were obtained from our previous study. No significant differences in fungal or bacterial alpha diversity or beta diversity were detected between recipients and donors, indicating an absence of broad community-level separation. Malassezia and Candida were the dominant fungal genera in both groups. Differential abundance analyses using ANCOM-BC2 and DESeq2 consistently identified lower Malassezia abundance in recipients, alongside predominantly lower abundance of several bacterial taxa. Cross-kingdom network analysis showed low Jaccard similarity in highly central taxa between donors and recipients, despite no significant differences in global network properties. This pattern persisted across most sample-size-matched subsamples. Conclusions These findings suggest that oral microbiome differences between kidney transplant recipients and donors are more apparent in specific taxonomic changes, particularly the reduction in Malassezia, and in the relative organisation of central community members than in broad shifts in overall microbial composition.