Mechanisms of intestinal flora in colorectal cancer

The intestinal flora is a complex community of microbes that inhabit the digestive tract and live with their hosts symbiotically. Several gastrointestinal diseases, such as colorectal cancer (CRC), have been associated with dysbiosis, an imbalance between beneficial and opportunistic pathogens. Dysbiosis breaks the mucosal barrier, leading to inflammation and cancer. Increased numbers of harmful bacteria, such as Escherichia coli (E. coli) and Enterotoxigenic Bacteroides fragilis (ETBF), have been associated with chronic inflammation and the release of carcinogenic mediators, increasing the chances of inflammatory dysplasia. Compared with a healthy person, CRC patients showed reduced bacterial diversity and abundance, while Firmicutes and Bacteroidetes were increased. Specific bacteria have also been linked to the development and progression of CRC, such as E. coli, ETBF, and Enterococcus faecalis. Therefore, the aim was to analyze the association between the gut microbiota and CRC. Further research could assess the advantages of modulating the intestinal flora as protection for high-risk patients against CRC, affecting disease prognosis and patients' life.