Location: Agroecosystems Management ResearchTitle: Catchment-scale export of antibiotic resistance genes and bacteria from an agricultural watershed in central Iowa
|NEHER, TIMOTHY - Iowa State University
|MA, LANYING - Iowa State University
|HOWE, ADINA - Iowa State University
|SOUPIR, MICHELLE - Iowa State University
Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2019
Publication Date: 1/10/2020
Citation: Neher, T.P., Ma, L., Moorman, T.B., Howe, A.C., Soupir, M.L. 2020. Catchment-scale export of antibiotic resistance genes and bacteria from an agricultural watershed in central Iowa. PLoS One. 15(1):e0227136. https://doi.org/10.1371/journal.pone.0227136.
Interpretive Summary: Swine and cattle production are widespread and important agricultural operations in Iowa. Manure produced by animal feeding operations (AFOs) is commonly applied to surrounding agriculture fields to improve soil fertility. Antibiotics are utilized by AFOs to maintain animal health. But this results in antibiotic residues and antibiotic resistant bacteria entering the environment. This study examined the presence of genes coding for antibiotic resistance in stream waters in the Blackhawk Lake watershed. Both antibiotic-resistant bacteria and resistance-genes were found in all catchments, but concentrations were greatest in catchments receiving animal manures. The early spring and late fall time-periods are determined to be associated with the highest risk of transporting ARGs through catchment outlet water. These data provide information that inform swine and cattle producers, watershed managers, and researchers about the impact of animal feeding operations on their waters.
Technical Abstract: Manure produced by animal feeding operations (AFOs) is commonly applied to surrounding agriculture fields as an agroeconomic practice to improve soil fertility and properly dispose of manure on-site. Antibiotics are utilized by AFOs to control, prevent, and treat disease in livestock animals. Manure from antibiotic treated livestock contains undigested active antibiotic metabolites that provides selective pressure and facilitates the spread of antibiotic resistance to the environment. This two year study monitors a wide range of antibiotic resistance genes (ermB, ermF (macrolides), tetA, tetM, tetO, tetW (tetracyclines), sul1, sul2 (sulfonamides), aadA2 (aminoglycosides), vgaA, and vgaB (pleuroutilins) and total fecal indicator bacteria (FIB) (E. coli and enterococci) and tylosin and tetracycline resistant enterococci in catchment outlet waters from a highly agriculturalized watershed. Samples were collected at catchment outlets with areas ranging from 221 to 804 hectares, a scale in which comparisons can be made between areas with and without manure application. Results of the total watershed analysis shows higher concentrations of FIB resistance indicators in the growing season (June-August) and higher ARG indicators in the pre-planting (March-May) and post-harvest (September-December) seasons. The manured catchment had significantly higher (p<0.05) percent tetracycline and tylosin resistant bacteria than the non manured catchment in 2017. Average ermB and tetM concentrations above limit of quantification (LOQ) from catchment outlet waters ranged from