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Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/6/2015 Publication Date: 7/21/2015 Publication URL: http://handle.nal.usda.gov/10113/61713 Citation: Agga, G.E., Arthur, T.M., Durso, L.M., Harhay, D.M., Schmidt, J.W. 2015. Antimicrobial-resistant bacterial populations and antimicrobial resistance genes obtained from environments impacted by livestock and municipal waste. PLoS One. 10(7). Interpretive Summary: This study compared the populations of antimicrobial-resistant bacteria and the presence of antimicrobial resistance genes within samples of livestock and municipal waste streams. Liquid and solid samples were collected from the discharge of municipal wastewater treatment facilities, cattle feedlot runoff catchment ponds, swine waste lagoons and environments considered low impact (a municipal lake and a prairie). Individual samples were processed by traditional culture techniques for antimicrobial-resistant bacteria to determine the prevalence and concentrations of resistant strains. In addition, the samples from each collection period were pooled by location and sample type. DNA was isolated from the pooled samples and analyzed for 83 antibiotic resistance genes. The prevalences and concentrations of antimicrobial-resistant bacteria were similar among the livestock and municipal sample sources. Individual antimicrobial resistance genes were distinct among agricultural, environmental, and municipal samples, with municipal samples harboring the highest number of antimicrobial resistance genes. In conclusion, we report that antimicrobial resistance is a very widespread phenomenon and that similar prevalences and concentrations of antimicrobial-resistant bacteria and antimicrobial resistance genes can be obtained from cattle, human, and swine waste streams, but a higher diversity of antimicrobial resistance genes can be found in human waste streams. Technical Abstract: This study compared the populations of antimicrobial-resistant bacteria and the repertoire of antimicrobial resistance genes in four environments: effluent of three municipal waste water treatment facilities, three cattle feedlot runoff catchment ponds, three swine waste lagoons, and two "low impact" environments (a municipal lake and a relict prairie). Multiple liquid and solid samples were collected from each environment. The prevalences and concentrations of antimicrobial-resistant (AMR) Gram-negative (Escherichia coli and Salmonella enterica) and Salmonella prevalences of 83 antimicrobial resistance genes in metagenomic DNA isolated from samples pooled (n= 44) by collection date, location, and sample type were determined. The prevalences and concentrations of AMR E. coli and S. Salmonella were similar among the livestock and municipal sample sources. The levels of erythromycin-resistant enterococci were significantly higher in cattle runoff and swine waste lagoon liquid samples compared to municipal samples, but not significantly different in solid samples. Similarly, trimethoprim/sulfamethoxazole-resistant E. coli concentrations were significantly higher in swine liquid than in municipal liquid samples, but there was no difference in solid samples. Individual antimicrobial resistance genes were significantly clustered within livestock, low impact, and municipal samples, with municipal samples harboring the highest number of antimicrobial resistance genes. The numbers of class A beta-lactamase, class C beta-lactamase, and fluoroquinolone resistance genes detected were significantly higher (P < 0.05) in municipal samples than in cattle runoff or swine lagoon samples. In conclusion, we report that AMR is a very widespread phenomenon and that similar prevalences and concentrations of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes exist in cattle, human, and swine waste streams, but a higher diversity of antimicrobial resistance genes are present in human waste streams. |
