Submitted to: Current Opinion in Biotechnology
Publication Type: Literature Review
Publication Acceptance Date: 7/25/2021
Publication Date: 9/4/2021
Citation: Haley, B.J., Van Kessel, J.S. 2021. The resistome of the bovine gastrointestinal tract. Current Opinion in Biotechnology. 73:213-219. https://doi.org/10.1016/j.copbio.2021.07.025.
Technical Abstract: Antimicrobial resistance is a significant human and animal health issue on a global scale and agriculture, specifically food animal production, has been presumed to play a major role in the emergence and spread of resistant human pathogens. The gastrointestinal tracts of dairy and beef cattle and calves are known reservoirs of antimicrobial resistant bacteria, and our knowledge of the ecology, diversity, and dynamics of resistance in these animals has dramatically changed with the advent of novel molecular technologies. Historically, data on resistance was primarily gathered by isolating Escherichia coli from fecal samples using traditional culturing methods and then screening these isolates for sensitivities to a panel of antimicrobials. These data are valuable but offer a relatively low-resolution estimation of resistance in the bovine gut since E. coli is a minor fraction of the gut community. Application of shotgun metagenomics and qPCR to the study of bovine gut ecology has allowed researchers to identify and quantify resistance genes across all bacterial host species. Recent studies have demonstrated that the bovine gut resistome is highly diverse with some similarities in resistance gene content to other animals, including humans. Recent work has also identified differences in the beef and dairy cow resistomes, as well as a greater abundance of resistance genes in very young calves than in older animals. Studies focused on antimicrobial administration and conventional versus organic production have yielded conflicting results indicating that more work is needed to determine the major drivers of resistance in the bovine gut. Future work should harness emerging metagenome sequencing technologies to include a greater number of animals and should also include identification of the bacterial taxa harboring the resistance genes to better understand the drivers of antimicrobial resistance in cattle and the potential public health risks of resistant bacteria in the bovine gut.