Characteristics of the Salivary Microbiota in Patients With Various Digestive Tract Cancers

Abstract

The salivary microbiota is constantly swallowed and delivered to the digestive tract. These bacteria may be associated with gastrointestinal diseases. This case-control study examined the salivary microbiota in patients with digestive tract cancer (DTC) and evaluated their differential distribution based on the cancer sites. We collected saliva samples from 59 patients with cancer in any part of the digestive tract (tongue/pharynx, esophagus, stomach, and large intestine) and from 118 age- and sex-matched control subjects. There was no significant difference in periodontal status between DTC patients and control subjects ( P = 0.72). We examined the bacterial diversity and composition in saliva by 16S ribosomal RNA gene sequencing. Salivary bacterial diversity in DTC patients was significantly higher than that in control subjects [number of operational taxonomic units (OTUs), P = 0.02; Shannon index, P < 0.01; Chao1, P = 0.04]. Eleven differentially abundant OTUs in DTC patients were identified using the linear discriminant analysis effect size (LEfSe) method. Based on the cancer sites, the diversity of salivary bacteria was especially higher in tongue/pharyngeal or esophageal cancer patients than in control subjects. Among the 11 differentially abundant OTUs in DTC patients, an OTU corresponding to Porphyromonas gingivalis was more abundant in the saliva of all groups of DTC patients compared to that in control subjects, and an OTU corresponding to Corynebacterium species was more abundant in all groups other than gastric cancer patients ( P < 0.01). In addition, the relative abundances of OTUs corresponding to Fusobacterium nucleatum , Streptococcus parasanguinis II, and Neisseria species were significantly higher in tongue/pharyngeal cancer patients compared to their abundances in control subjects ( P < 0.01). The relative abundance of an OTU corresponding to the Neisseria species was also significantly higher in gastric cancer patients and that of an OTU corresponding to Actinomyces odontolyticus was significantly higher in colorectal cancer patients ( P < 0.01). These results suggest that the salivary microbiota might be associated with various digestive tract cancers.

Oral health and gastrointestinal cancer: A nationwide cohort study

“…First, the systemic spread of oral bacteria could enable oral disease to affect gastric tissue. Oral bacterial infections, including with Porphyromonas gingivalis , can be closely associated with GI cancer (Kageyama et al., 2019; Yuan et al., 2017). The dissemination of oral bacteria by swallowing saliva, which contains a large number of bacteria, could explain its involvement in inflammation in the GI tract (Nasidze, Li, Quinque, Tang, & Stoneking, 2009; Socransky & Haffajee, 2005).…”

Characterization of the Esophageal Microbiota and Prediction of the Metabolic Pathways Involved in Esophageal Cancer

“…Alpha diversity indexes were calculated using MOTHUR (version 1.30.1) (Schloss et al, 2009 ). Principal coordinates analysis (PCoA) based on the weighted and unweighted UniFrac distance and analysis of similarities (ANOSIM) was carried out to compare the global microbial composition at the operational taxonomic unit (OTU) level (Kageyama et al, 2019 ). Welch's t- test and the Wilcoxon rank-sum test were used to identify species at phylum and genus levels.…”

“…The detection of discriminant bacterial species was performed using the linear discriminant analysis effect size (LEfSe) (Segata et al, 2011 ). The linear discriminant analysis score (LDA score) indicated the effect size of each OTU, and OTUs with an LDA score >3.0 were defined as differentially abundant OTUs (Yang et al, 2018 ; Kageyama et al, 2019 ). Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) (Langille et al, 2013 ) analysis was used to identify Kyoto Encyclopedia of Genes and Genomes (KEGG) biochemical pathways, and the results were visualized as a heatmap with the Multiple Experiment Viewer (version 4.9.0).…”

The salivary microbiota in health and disease

“…Accordingly, high salivary levels of T. forsythia and A. actinomycetemcomitans and low bacterial diversity were reported in patients with precancerous gastric lesions [82]. On the other hand, gastrointestinal cancers of various origins were associated with an increased salivary bacterial diversity and high levels of P. gingivalis as compared to matched healthy controls [83]. In line, a study from 2019 used NGS of SM to discriminate patients with throat cancer from healthy controls and patients with vocal cord polyps with an AUC = 0.87 [84].…”