Microbiota Dysbiosis a Cause of Colorectal Cancer or Not? A Systematic Review

Deaths from colorectal cancer (CRC) are still rising, and various links to etiology have been proposed. However, a direct link between microbial dysbiosis and colorectal cancer has not been postulated. This study aimed to identify the role of microbes in the pathogenesis of colorectal cancer. This systematic review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A systematic search was done considering papers published over the past 12 years, using PubMed, PubMed Central, Cochrane, Google Scholar, and ScienceDirect databases. Studies were selected based on the following predefined eligibility criteria: English-language systematic reviews, meta-analysis, randomized controlled trials (RCTs), and clinical trials, which included papers on microbes playing roles in colorectal cancer with the derived data transferred to a template. Following this, quality assessment was done using each study's relevant assessment tool. The initial search generated 128 studies. From the study, we found the ratio of Fusobacterium, when compared between healthy and colorectal cancer patients' guts, was the highest, although it was not the most predominant gut organism. Enterotoxigenic Bacteroides fragilis (ETBF), Clostridium and Salmonella, and Peptostreptococcus showed links with colorectal cancer and described pathways that could explain its implication in colorectal cancer. However, overt conclusions cannot be drawn because further research needs to be conducted.