Impact of vegetative treatment system on multiple measures of antibiotic resistance in agricultural wastewater

Authors: Durso, Lisa; Miller, Daniel; HENRY, CHRISTOPHER - University Of Arkansas

Submitted to: International Journal of Environmental Research and Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2018
Publication Date: 6/21/2018
Citation: Durso, L.M., Miller, D.N., Henry, C.G. 2018. Impact of vegetative treatment system on multiple measures of antibiotic resistance in agricultural wastewater. International Journal of Environmental Research and Public Health. 15(6):1295. http://dx.doi.org/10.3390/ijerph15071295.
DOI: https://doi.org/10.3390/ijerph15071295

Interpretive Summary: There is concern that antibiotic resistant bacteria and antibiotic resistance genes from food animal production can be transported through the environment, and eventually end up contributing to untreatable infectious disease in people and animals. One route by which this is thought to occur is via manure-contaminated waters that are applied onto land, or that runoff into surface waters. These agricultural wastewaters are a rich source of many types of bacteria, including bacteria that carry antibiotic resistance genes. In this study we evaluated a system designed to treat runoff from a beef cattle feedlot, and keep the bacteria and genes out of surface waters. Called a Vegetative Treatment System (VTS), this structure consisted of holding ponds that collected the manure-contaminated wastewater that ran off of the feedlot pen following rain or snow melt, and then distributed it onto grassy fields where the nutrients were used to grow hay. We measured tetracycline and cefotaxime resistant bacteria and characterized bacterial isolates from the site, for three years. Bacteria were characterized for carriage of tetracycline resistance genes, tested to determine multi-drug resistance profiles. Tetracycline resistance in feedlot runoff wastewater was 2 to 3 orders of magnitude higher compared to rainfall runoff from the VTS fields, indicating efficacy of the VTA for reducing ARB over time following wastewater application. Clear differences in MDR profiles were observed based on the specific media on which a sample was plated. This result highlights the importance of method, especially in the contest of isolate-based surveillance and monitoring of ARB in agricultural wastewaters.

Technical Abstract: Wastewater is an important vector of antibiotic resistant bacteria, and antibiotic resistance genes (ARB/G). While there is broad agreement that ARB/G from agricultural wastewaters can be transported through the environment and contribute to untreatable infectious disease in humans and animals, there remain large knowledge gaps surrounding applied details on the types and amounts of ARB/G associated with different agricultural wastewater treatment options and different ag production systems. This study evaluates a vegetative treatment system (VTS) built to treat the wastewater from a beef cattle feedlot. Samples were collected for three years, and plated on multiple media types to enumerate tetracycline and cefotaxime-resistant bacteria. Isolates (n=XXX) were characterized for carriage of tetracycline resistance genes, and E. coli isolates (n=XXX) were phenotyped to determine multi-drug resistance (MDR) profiles. Tetracycline resistance in feedlot runoff wastewater was 2 to 3 orders of magnitude higher compared to rainfall runoff from the VTS fields, indicating efficacy of the VTA for reducing ARB over time following wastewater application. Clear differences in MDR profiles were observed based on the specific media on which a sample was plated. This result highlights the importance of method, especially in the contest of isolate-based surveillance and monitoring of ARB in agricultural wastewaters.