Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2017
Publication Date: N/A
Interpretive Summary: Poultry litter (PL) is a mixture of manure, bedding, feathers and spilled feed. PL is periodically removed from poultry production facilities and applied to soil where it serves as a valuable nutrient source and soil conditioner. However, the high volume of PL produced and applied in some regions raises concerns about contamination from nutrients, bacteria and runoff. Subsurface application of PL has been used in areas of concentrated poultry production to maximize the fertilizer value of PL and reduce runoff of nutrients. However, the effect of this practice on microbial populations with genes for antibiotic resistance (AR) is unknown. We quantified the concentration of four genes associated with AR. Results show that soils with banded PL had higher concentrations of genes for AR and that they persisted for longer than in soils with broadcast applied PL. These data suggest that subsurface application of biological soil amendments may increase the persistence of bacteria with antibiotic resistance.
Technical Abstract: The objective of this study was to determine the concentration of AR genes for sulfonamide (sulI), tetracycline (tetW), streptomycin (strpB) and for the class one integrase (intI1) gene in soils with subsurface banded PL. Field scale plots were established with triplicate treatments of either no fertilizer, conventional fertilizer, surface broadcast PL or subsurface banded PL. Soil sample cores (10cm) were taken from each treatment and AR gene concentrations in soil DNA extracts were analyzed by quantitative PCR. Concentrations of genes for resistance to sulfonamide and tetracycline and for the integrase gene were high (0.2 to 3.0 X 108 copies gene g-1) in the PL used for application. After application AR gene concentrations increased within one day in soils with broadcast PL (0.1 to 4.0 X 106 copies gene g-1) but were below detection in samples taken 133 days after application. In soils with banded PL, AR gene concentrations were not different than background one day after application, but were high in samples taken 21 days after application (0.5 to 40 X 106 copies gene g-1) and levels remained above background for at least 133 days. These data suggest that subsurface banding may increase the concentration of bacteria with AR genes within the bands and that populations may persist for significantly longer than those associated with broadcast PL application.