Oral microbiota and salivary levels of oral pathogens in gastro‐intestinal diseases: Current knowledge and exploratory study

Various bi‐directional associations exist between oral health and gastro‐intestinal diseases. The oral microbiome plays a role in the gastro‐intestinal carcinogenesis and fusobacteria are the most investigated bacteria involved. This paper aims to review the current knowledge and report the preliminary data on salivary levels of Fusobacterium nucleatum, Porphyromonas gingivalis and Candida albicans in subjects with different gastro‐intestinal conditions or pathologies, in order to determine any differences. The null hypothesis was “subjects with different gastro‐intestinal diseases do not show significant differences in the composition of the oral microbiota”. Twenty‐one subjects undergoing esophagastroduodenoscopy or colonscopy were recruited. For each subject, a salivary sample was collected before the endoscopy procedure, immediately stored at ‐20°C and subsequently used for genomic bacterial DNA extraction by real‐time PCR. Low levels of F. nucleatum and P. gingivalis were peculiar in the oral microbiota in subjects affected by Helicobater pylori‐negative chronic gastritis without cancerization and future studies will elucidate this association. The level of C. albicans did not statistically differ among groups. This preliminary study could be used in the future, following further investigation, as a non‐invasive method for the search of gastrointestinal diseases and associated markers.