Alterations in the oral and gut microbiome of colorectal cancer patients and association with host clinical factors

Previous studies have suggested that gut microbiota plays a critical role in colorectal cancer (CRC). Although preliminary comparisons of the oral and gut microbiota between CRC and healthy control (HC) patients have been made, the association between microbiome abundance and host clinical factors has not been fully illustrated, especially oral health conditions. Matching samples of unstimulated saliva, cancer tissues or biopsies and stools were collected from 30 CRC and 30 HC patients from Shanghai Jiao Tong University affiliated Renji Hospital for 16S rRNA sequencing analysis. The diversity in salivary and mucosal microbiome, but not stool microbiome of CRC group, was significantly different from that of HC, as demonstrated by the Principal Component Analysis. Logistic regression analysis revealed that older age and higher oral hygiene index (OHI) were independent risk factors for CRC, with odds ratios and 95% confidence intervals of 1.159 (1.045‐1.284) and 4.398 (1.328‐14.567), respectively. Salivary Firmicutes to Bacteroides ratio in CRC was significantly higher than that in the HC group (P