The gut microbiome and colorectal cancer: a review of bacterial pathogenesis

Colorectal cancer (CRC) is the third most common newly diagnosed cancer in both men and women in the Unites States. Colonoscopy has become increasingly popular in CRC screening and represents the gold standard for detecting and removing pre-cancerous lesions. Although colonoscopy is considered a relatively safe procedure, it is invasive and bowel preparation can be challenging for patients. As interest in the gut microbiome has expanded, there have been new links established between bacteria and the development of CRC. These developing associations could prove to be a useful adjunct to colonoscopy for CRC screening in the future. This review examines current research evaluating multiple proposed pathogenic microorganisms including sulfidogenic bacteria such as Bilophila wadsworthia, as well as Streptococcus bovis, Helicobacter pylori, Bacteroides fragilis, and Clostridium septicum. This discussion primarily focuses on bacterial pathogenesis, evidence of association with CRC, and the proposed mechanisms of carcinogenesis.