Oral microbiome and history of smoking and colorectal cancer

Abstract

Background: The equilibrium of oral microbiome may be altered by environmental factors, including cigarette smoking. Severalrecent studies also suggest that oral pathogens causing periodontal disease, such as Fusobacterium nucleatum, are involved inpathogenesis of colorectal cancer.

Methods: For this study oral rinse DNA samples from 190 participants in a population-based case-control study for colorectalcancer were used to amplify a V3-V4 region of bacterial 16S rRNA gene. The amplicons were sequenced using Illumina MiSeqpaired end chemistry on two runs, yielding approximately 35 million filtered reads which were assigned to bacterial phyla.

Results: No association was found between Fusobacterium abundance or presence and colorectal cancer. However, adjustedfor age and experimental batch, colorectal cancer history was associated with increased presence of genus Lactobacillus andincreased relative abundance of Rothia by 28% and current smoking was associated with a 33% decrease in relative counts of Betaproteobacteria (primarily Neisseria) and 23% increase in relative abundance of Veillonellaceae family. We also found thatsmoking had significant effects on the 2^nd component scores and 2^nd coordinate distances in principal component and coordinateanalyses.

Conclusions: It remains to be elucidated whether the observed differences can be translated into biochemical changes in oralenvironment, thus potentially affecting oral health.