A global rise in antimicrobial resistance among pathogenic bacteria has proved to be a major public health threat, with the rate of multidrug-resistant bacterial infections increasing over time. The gut microbiome has been studied as a reservoir of antibiotic resistance genes (ARGs) that can be transferred to bacterial pathogens via horizontal gene transfer (HGT) of conjugative plasmids and mobile genetic elements (the gut resistome). Advances in metagenomic sequencing have facilitated the identification of resistome modulators, including live microbial therapeutics such as probiotics and fecal microbiome transplantation that can either expand or reduce the abundances of ARG-carrying bacteria in the gut. While many different gut microbes encode for ARGs, they are not uniformly distributed across, or transmitted by, various members of the microbiome, and not all are of equal clinical relevance. Both experimental and theoretical approaches in microbial ecology have been applied to understand differing frequencies of ARG horizontal transfer between commensal microbes as well as between commensals and pathogens. In this commentary, we assess the evidence for the role of commensal gut microbes in encoding antimicrobial resistance genes, the degree to which they are shared both with other commensals and with pathogens, and the host and environmental factors that can impact resistome dynamics. We further discuss novel sequencing-based approaches for identifying ARGs and predicting future transfer events of clinically relevant ARGs from commensals to pathogens.

In this single institution retrospective medical record review, patients diagnosed with colorectal cancer from the years 2018-2022 were evaluated to distinguish an associative linear relationship between diagnosed colorectal cancer and a positive result for the presence of a microorganism. Based on the clinical incidence of this occurrence, it was observed patients with tumors in the left side of the colon had a higher incidence of a positive test result with a dominant microorganism. Species evaluation within this cohort found similarity to microorganisms identified as colorectal cancer biomarkers. These findings support clinical relevance and warrant further consideration for prospective study regarding microorganism involvement in colorectal cancer.