Comparison of oral and intestinal human microbiota and association of Fusobacterium nucleatum infection in patients with colorectal cancer: A pilot study
Edda Russo, Giovanni Bacci, Carolina Chiellini, Camilla Fagorzi, Elena Niccolai, Antonio Taddei, Federica Ricci and Amedeo Amedei,
University of Florence, Italy
Azienda Ospedaliera Universitaria Careggi (AOUC) Florence, Italy
The study used next-generation sequencing (NGS) to analyze and compare human microbiota from three different environments, saliva, feces, and cancer tissue (CT), of a selected cohort of 10 Italian patients with colorectal cancer (CRC) vs. 10 healthy controls (saliva and feces). Furthermore, the Fusobacterium nucleatum (F. nucleatum) abundance in the same districts was investigated trough quantitative polymerase chain reaction (RT-qPCR) to assess the association with CRC. The difference of bacterial taxonomic composition, F. nucleatum abundance between CRC and healthy controls and the relationship of F. nucleatum presence with clinical variables were evaluated. Taxonomic analysis revealed the presence of three main bacterial phyla, which comprises ca. 80% of reads: Firmicutes (39.18%), Bacteroidetes (30.36%), and Proteobacteria (10.65%). The three examined environments showed different bacterial assemblages; in particular, we observed the enrichment of members of Bacteroidetes within fecal samples of CRC patients, while Firmicutes were over-represented in the fecal samples of healthy controls. The CT samples show the highest alpha diversity values. F. nucleatum in patients was shown to be more abundant in saliva samples than in feces samples and, notably related to the presence of metastases. These results highlight a different taxonomic composition of feces from CRC compared to healthy controls and that the F. nucleatum presence is positively associated with the clinical course of CRC patients (metastasis). So, our results could be useful to promote the development of novel bacteria-related diagnostic tools and therapeutic interventions in CRC patients.