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ARS Home » Midwest Area » Bowling Green, Kentucky » Food Animal Environmental Systems Research » Research » Publications at this Location » Publication #315832

Research Project: Efficient Management and Use of Animal Manure to Protect Human Health and Environmental Quality

Location: Food Animal Environmental Systems Research

Title: Antibiotic resistance gene concentrations in agroecosystems following beef manure or poultry litter deposition

Author
item Cook, Kimberly - Kim
item Netthisinghe, Annesly - Western Kentucky University
item Gilfillen, Rebecca - Western Kentucky University

Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2015
Publication Date: 5/17/2015
Citation: Cook, K.L., Netthisinghe, A., Gilfillen, R. 2015. Antibiotic resistance gene concentrations in agroecosystems following beef manure or poultry litter deposition. 3rd International Symposium on the Environmental Dimension of Antibiotic Resistance. May 17-21, 2015. Wernigerode, Germany.

Interpretive Summary: Antibiotics are commonly used in livestock production to promote growth and combat disease. However, as much as 80% of the drug may pass through the animal and into the soil where selective pressure may favor survival of antibiotic resistant bacteria. Recent studies have shown that there is also a potential for spread of antibiotic resistance genes (ARG) to the environment following application of livestock manures. In this study, concentrations of bacteria with ARG in soils with applied poultry litter (PL; 2 years) or from a beef cattle backgrounding operation (BB; 3 year) were determined. Samples were taken (1) following PL application to soils under conventional or no till management and (2) from soils taken from the BB while livestock were on-site and following their removal. Microbial populations with resistance to tetracycline, erythromycin and sulfonamides were quantified. In soils with applied PL, concentrations of ARG for sulfonamide and tetracycline resistance increased following PL application but were near background by the end of the season. Concentrations of bacteria with AR genes were highly variable across the BB landscape, but in general initial concentrations averaged between 2.5 and 3.3 OM higher in the dirt congregation areas than in grassy areas. These results suggest that the concentration of bacteria with ARG significantly increase in soils where manures are deposited but levels are mitigated by time and landscape management. Future research should determine which AR populations remain in soils and to identify intervention strategies to limit their impact outside of the agricultural environment.

Technical Abstract: Antibiotics are commonly used in livestock production to promote growth and combat disease. However, as much as 80% of the drug may pass through the animal and into the soil where selective pressure may favor survival of antibiotic resistant bacteria. Recent studies have shown that there is also a potential for spread of antibiotic resistance genes (ARG) to the environment following application of livestock manures. In this study, concentrations of bacteria with ARG in soils with applied poultry litter (PL; 2 years) or from a beef cattle backgrounding operation (BB; 3 year) were determined. Samples were taken (1) following PL application to soils under conventional or no till management and (2) from soils taken from the BB while livestock were on-site and following their removal. Microbial populations with genes conferring resistance to tetracycline (tetQ and tetW), erythromycin (ermB and ermF) or sulfonamides (sulI), were quantified using quantitative, real-time (qPCR) analysis. In soils with applied PL, concentrations of ARG for sulfonamide and tetracycline resistance increased up to 3.0 orders of magnitude (OM; mean concentrations 2.6 to 6.9 x 108 copies g-1) following PL application but were near background by the end of the season. Concentrations of bacteria with AR genes were highly variable across the BB landscape, but in general initial concentrations averaged between 2.5 and 3.3 OM higher in the dirt congregation areas than in grassy areas. Two years after removal of animals from the site, concentrations of bacteria with ARG were at least one OM (90%) lower. The highest concentration of ARG remaining in those soils (2.1 ± 3.2 X 109 copies g-1) and background in grass (4.8 ± 3.5 X 106 copies g-1) were for sulfonamide resistance. These results suggest that the concentration of bacteria with ARG significantly increase in soils where manures are deposited but levels are mitigated by time and landscape management. Future research should determine which AR populations remain in soils and to identify intervention strategies to limit their impact outside of the agricultural environment.