Fungal-Bacterial Interactions in Oral Candidiasis and Periodontal Disease: A Narrative Review

Fungal-bacterial interactions in the oral environment represent a multidimensional and underexplored aspect of oral microbiology and pathogenesis. Polymicrobial biofilms involving Candida albicans and periodontopathogenic bacteria such as Streptococcus mutans , Fusobacterium nucleatum , and Porphyromonas gingivalis exhibit enhanced virulence, stability, and pathogenic synergy. These multispecies communities engage in cooperative processes including mutualistic adhesion, metabolite cross-feeding, interkingdom quorum sensing, and the formation of robust extracellular matrices. Such interactions facilitate colonisation, promote immune evasion, and reduce the efficacy of conventional antifungal and antibacterial therapies. This review examines the molecular mechanisms underlying these interkingdom interactions, including adhesion, metabolic cooperation, signalling pathways, and biofilm architecture, as well as metabolic modulation and environmental buffering, along with their clinical relevance in oral candidiasis and periodontal disease. A deeper understanding of these polymicrobial systems is essential for the development of advanced diagnostics, targeted therapeutics, and effective biofilm-disrupting strategies in oral healthcare.