Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2011
Publication Date: 1/31/2012
Citation: Looft, T.P., Johnson, T., Allen, H.K., Bayles, D.O., Alt, D.P., Cole, J., Hashsham, S., Stedtfeld, R., Stedtfeld, T., Chai, B., Tiedje, J., Stanton, T.B. 2012. In-feed antibiotic effects on the swine intestinal microbiome. Proceedings of the National Academy of Sciences. 109(5):1691-1696. Interpretive Summary: For over 50 years, antibiotics have been administered to farm animals to control disease, promote feed efficiency, or both. The impact of animal antibiotic use on the treatment of human diseases is hotly debated. In these studies, computer based analyses of DNA sequences and quantitative PCR analysis of antibiotic resistance genes were used to analyze bacterial species and bacterial genes in swine fecal samples. We found that antibiotic resistance genes increased in both abundance and diversity in the swine microbiome in response to feeding a common commercial antibiotic mix (ASP250). Resistance genes for the ASP250 antibiotics increased in numbers and, surprisingly, so did some resistance genes to antibiotics not in ASP250, demonstrating the potential for antibiotic treatments to select for unrelated resistance genes. Additional effects of antibiotic treatment included an increase in Escherichia coli populations and in microbial genes relating to energy production and conversion. Possible collateral effects of agricultural antibiotics should be considered in cost-benefit analyses of antibiotic use.
Technical Abstract: Antibiotics have been administered to agricultural animals for disease treatment, disease prevention, and growth promotion for over 50 years. The impact of such antibiotic use on the treatment of human diseases is hotly debated. Based on metagenomic and qPCR analysis, we show that antibiotic resistance genes increase in abundance and diversity in the swine microbiome in response to antibiotic (ASP250) treatment. Some of these genes confer resistance to antibiotics not administered in this study, demonstrating the potential for co-selection for resistance to different classes of antibiotics. Additional effects of antibiotic treatment include an increase in Escherichia coli and in microbial functions relating to energy production and conversion. The collateral effects of agricultural antibiotics are apparent and must be considered in cost-benefit analyses of antibiotic use.