Alterations in the feline oral microbiome in common oral diseases - A comprehensive review

The most prevalent diagnostic conditions in domestic cats (Felis catus) are oral diseases, affecting up to 90% of older cats. Periodontal disease (PD), feline chronic gingivostomatitis (FCGS), and tooth resorption (TR) are the principal clinically relevant entities, each with distinct histopathological and microbiological features. Certain molecular techniques, including 16S rRNA sequencing, shotgun metagenomics, and metatranscriptomics, have substantially advanced our understanding of the feline oral microbiome alterations. This review summarizes the findings of the healthy oral microbiome and its disease-associated shifts in PD, FCGS, TR, and feline immunodeficiency virus (FIV)-associated pathology. The healthy oral cavity is dominated by Proteobacteria, Bacteroidota, Bacillota, Fusobacteria, and Actinobacteria, notably Porphyromonas, Moraxella, Capnocytophaga, and Fusobacterium. Dental disease is characterised by expansion of Bacteroidota and Spirochaetota, enrichment of Treponema, Peptostreptococcus, Filifactor, and Fusobacterium nucleatum, and depletion of commensals. The contributions of fungi, viruses, and host immunity are critically evaluated, alongside the development of microbiome-based diagnostics and therapeutics. We argue that dysbiosis is a unifying (albeit not monocausal) feature of feline oral pathology and identify gaps in current knowledge that require further investigation.