Antibiotic resistance genes in swine manure slurry as affected by pit additives and facility disinfectants

Authors: HALL, MARIA - University Of Nebraska; BARTELT-HUNT, SHANNON - University Of Nebraska; Gilley, John; ESKRIDGE, KENT - University Of Nebraska; LU, XI - University Of Nebraska; SNOW, DANIEL - University Of Nebraska

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2020
Publication Date: 11/3/2020
Citation: Hall, M.C., Bartelt-Hunt, S.L., Gilley, J.E., Eskridge, K.M., Lu, X., Snow, D.D. 2020. Antibiotic resistance genes in swine manure slurry as affected by pit additives and facility disinfectants. Environmental Pollution. 761(2021):143287. https://doi.org/10.1016/j.scitotenv.2020.143287.
DOI: https://doi.org/10.1016/j.scitotenv.2020.143287

Interpretive Summary: Manure storage facilities are critical control points to reduce antibiotic resistance genes in swine manure slurry before the slurry is land applied. However, little is known about how chemicals entering the manure storage facilities may affect the fate of antibiotic resistance genes. The objective of this study was to analyze the impact of six commonly used pit additives and four facility disinfectants on the concentration of antibiotic resistance genes in swine manure slurry. Bench scale reactors, each containing approximately 50 liters of liquid swine manure, were dosed with additives or disinfectants and were sampled for 40 days. Seven antibiotic resistance genes were monitored. Out of the six additives tested, one additive significantly reduced the time-averaged absolute abundance of antibiotic resistance genes as compared to the no additive control. Out of the four disinfectants tested, one disinfectant significantly reduced the time-averaged absolute abundance of selected antibiotic resistance genes compared to the no-disinfectant control. Overall, the disinfectants were more effective in controlling the absolute abundance of antibiotic resistance genes than were the pit additives.

Technical Abstract: Manure storage facilities are critical control points to reduce antibiotic resistance genes (ARGs) in swine manure slurry before the slurry is land applied. However, little is known about how exogenous chemicals entering the manure storage facilities may affect the fate of ARGs. The objective of this study was to analyze the impact of six commonly used pit additives and four facility disinfectants on the concentration of ARGs in swine manure slurry. Bench scale reactors, each containing approximately 50 L of liquid swine manure, were dosed with additives or disinfectants and were sampled for 40 days. Seven antibiotic resistance genes along with the intI1 gene and the 16S rRNA gene were monitored. Out of the six additives tested, Sludge Away significantly reduced the time-averaged absolute abundance of erm(C), erm(F), tet(Q), and the 16S rRNA gene as compared to the no additive control. Out of the four disinfectants tested, Tek-Trol significantly reduced the time-averaged absolute abundance of erm(B), erm(C), erm(F), intI1, tet(Q), and tet(X) than did the no-disinfectant control. According to Spearman’s rank correlation, three genes erm(F), tet(Q), and tet(X) showed a strong to perfectly positive correlation and the two genes erm(B) and tet(O) showed a moderate to strong correlation in both the additive and disinfectant tests. Overall, the disinfectants were more effective in controlling the absolute abundance of ARGs than were the pit additives.