Oral Dysbiosis in Oral Squamous Cell Carcinoma (OSCC).
Background: Oral dysbiosis plays an important role in pathogenesis of oral squamous cell carcinoma (OSCC). Our study aimed to perform pairwise comparison of oral microbiota, especially the bacteriome, of OSCC tumoral surface vs healthy oral mucosa and supragingival dental plaque samples and evaluate the association of a novel bacteriome-based Oral Dysbiosis Index (bbODI) with the OSCC surface.  Methods: This pilot observational study used in total 84 patient-matched samples from 21 patients with OSCC. Samples were taken from OSCC tumoral surface (swabs and biopsies), healthy oral mucosa (tongue and buccal swabs), and supragingival dental plaque swabs. Bacteriomes from all types of swabs were analyzed by 16S rRNA amplicon sequencing. The presence of microscopic fungi was evaluated in buccal swabs using conventional culture techniques, and immunohistochemical analysis of selected viruses was performed in paraffin-embedded tumor tissues.  Results: The bacteriome a-diversity indices were similar among all studied matrices. The relative abundance of genus Fusobacterium, ratio of relative abundances of gram-negative to gram-positive bacterial genera, and the bbODI significantly differed on the tumor surface vs patient-matched healthy oral mucosa (both buccal and tongue swabs) and supragingival dental plaque samples. Oral candidosis was found in 25 % of patients; all patients were negative for cytomegalovirus and Epstein-Barr virus.  Conclusions: Our study showed that certain characteristics of bacteriome composition of the OSCC surface differ from patient-matched samples of healthy oral mucosa and supragingival dental plaque. The proposed bbODI appears to be a promising non-invasive tool for identification of bacteriome disruption on OSCC surface.