Location: Agroecosystems Management ResearchTitle: Fate and transport of antibiotic resistant bacteria and resistance genes in artificially drained agricultural fields receiving swine manure application Author
|Luby, Elizabeth - Iowa State University|
|Moorman, Thomas - Tom|
|Soupir, Michelle - Iowa State University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/17/2014
Publication Date: 5/17/2014
Citation: Luby, E., Moorman, T.B., Soupir, M. 2014. Fate and transport of antibiotic resistant bacteria and resistance genes in artificially drained agricultural fields receiving swine manure application [abstract]. American Society for Microbiology General Meeting. Available at: http://www.asmonlineeducation.com/php/asm2014abstracts/data/index.htm.
Technical Abstract: While previous studies have examined the occurrence of antibiotic resistant bacteria and antibiotic resistant genes around confined swine feeding operations, little information is known about their release and transport from artificially drained fields receiving swine manure application. Much of the Midwestern farm land has artificial subsurface drains that lower the water table by draining water into nearby surface waters. The study site consisted of four one acre fields each in a two year corn-soybean rotation. The four plots received one of two treatments: swine manure or urea and ammonium nitrate fertilizer (control fields). The selected plots were managed as either no-till or chisel plowed in the spring prior to planting. We measured tylosin, tylosin-resistant enterococci and resistance genes in the soil and drainage samples. The macrolide resistance genes msrA, ermC, ermB, and ermF were enumerated through qPCR. The average enterococci concentration for samples taken from manure bands was 284 cfu/gdw of soil, with 96% demonstrating resistance to tylosin. Average concentrations of enterococci were significantly lower in inter-band and control plot samples at 11 and 35 cfu/gdw of soil, with none being resistant to tylosin. The ermB in soil samples demonstrated decreasing concentrations over time, but were still quantifiable a year after application. Manure bands were no longer detectable in the plots a year after application. ErmC genes in fall 2012 soil samples were only detected in the manure bands of the chisel and no-till plots. There were no significant differences in the enterococci and tylosin resistant enterococci in drainage water between control and manured plots (p>0.10), ermB had significantly higher copy numbers (p<0.01) in the drainage water from the manured plots compared to the water from the controls. Additionally, ermB concentrations were significantly higher in the no till manured plot than the chisel plow plot. This difference may be attributed to the formation of macropores in the no till fields, which allows for rapid transport of surface intake to drainage lines placed under the plots. Preliminary results have indicated resistance genes persisting soil samples collected from manure applied fields, but variable levels of significance in drainage flow samples.