Gut microbiota in colorectal cancer: Evidence from observational studies

This study proposes to update knowledge about the relationship between microbiota and Colorectal Cancer (CRC). This is a review carried out using the methodology of the Preferred Report Item for Systematic Analysis and Meta-Analysis (PRISMA) and search for original articles, indexed in the Pubmed, Cochrane and Science Direct databases, published between 2011 and 2019, in English. Ten articles showed changes in bacterial composition and its influence on the development and progression of CRC, and only two addressed changes in the composition of fungi and their relationship with CRC. Most studies have shown that the increase in Fusobacterium nucleatum and bacteroides fragilis is strongly associated with the occurrence of CRC due to inflammatory mechanisms; and that Faecalibacterium prausnitzii is a protective factor through the production of butyrate. Additional research is recommended to assess the relationship of microorganisms with the development of CRC, with an emphasis on fungi.