Deciphering the identity of oral and gut bacteria in colorectal cancer

Lisa Alves Azevedo

Key information

Authors:

Lisa Alves Azevedo (Lisa Alves Azevedo)

Supervisors:

Leonilde de Fátima Morais Moreira (Leonilde de Fátima Morais Moreira); Paul O’Toole

Published in

11/26/2018

Abstract

Colorectal cancer (CRC) is consistently the third deadliest cancer worldwide. Recent research has established that an altered community of bacteria (dysbiotic microbiota) is a feature of CRC and has questioned if these bacteria can be derived partly from the oral cavity. In this work, CRC patients were recruited, and a broad range approach was developed that includes histology and immunology techniques; microbiota metagenomic profiling; and a complete culture, isolation and identification methodology exploring multiple conditions that targeted faecal, oral and tumour bacteria of CRC patients. Oral colonization in CRC tumours was investigated by culturing and isolating bacteria from colonic tumours and oral swabs of 2 CRC patients; identifying bacteria by sequencing an amplicon from the full length 16S rRNA gene by Sanger sequencing; and performing random amplified polymorphic DNA (RAPD) genetic fingerprinting of strains to compare the genomic structure of oral and colonic isolates of the same species. Oral colonization in CRC tumours was demonstrated by successful culture from both locations of a considerable range of isolated species - 15 species belonging to 6 different families and 2 phyla - whose ability to elicit inflammation, cytokine production and cell proliferation can now be investigated. This project allowed the creation of a defined phylogenetic collection with 500 pure archived cultures, belonging to 95 different species (containing 10 strains considered until now uncultured and unsequenced by the Human Microbiome Project), 28 families and 5 phyla. Their future study might bring new insights into CRC disease mechanisms.