title: Impact of dairy manure pre-application treatment on manure composition, soil dynamics of antibiotic resistance genes, and abundance of antibiotic-resistance genes on vegetables at harvest.
abstract: Manuring ground used for crop production is an important agricultural practice. Should antibiotic-resistant enteric bacteria carried in the manure be transferred to crops that are consumed raw, their consumption by humans or animals will represent a route of exposure to antibiotic resistance genes. Treatment of manures prior to land application is a potential management option to reduce the abundance of antibiotic resistance genes entrained with manure application. In this study, dairy manure that was untreated, anaerobically digested, mechanically dewatered or composted was applied to field plots that were then cropped to lettuce, carrots and radishes. The impact of treatment on manure composition, persistence of antibiotic resistance gene targets in soil following application, and distribution of antibiotic resistance genes and bacteria on vegetables at harvest was determined. Composted manure had the lowest abundance of antibiotic resistance gene targets compared to the other manures. There was no significant difference in the persistence characteristics of antibiotic resistance genes following land application of the various manures. Compared to unmanured soil, antibiotic resistance genes were detected more frequently in soil receiving raw or digested manure, whereas they were not in soil receiving composted manure. The present study suggests that vegetables grown in ground receiving raw or digested manure are at risk of contamination with manure-borne antibiotic resistant bacteria, whereas vegetables grown in ground receiving composted manure are less so.
authors.affiliation: Agriculture and Agri-Food Canada, London, ON N5V 4T3, Canada.
authors.forename: Yuan-Ching
authors.initials: YC
authors.lastname: Tien
authors.affiliation: Graduate School at Shenzhen, Tsinghua University, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Li
authors.affiliation: Environmental Biotechnology Laboratory, University of Hong Kong, Hong Kong.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Agriculture and Agri-Food Canada, London, ON N5V 4T3, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Scott
authors.affiliation: Agriculture and Agri-Food Canada, London, ON N5V 4T3, Canada.
authors.forename: Roger
authors.initials: R
authors.lastname: Murray
authors.affiliation: Agriculture and Agri-Food Canada, London, ON N5V 4T3, Canada.
authors.forename: Lyne
authors.initials: L
authors.lastname: Sabourin
authors.affiliation: Agriculture and Agri-Food Canada, London, ON N5V 4T3, Canada.
authors.forename: Romain
authors.initials: R
authors.lastname: Marti
authors.affiliation: Agriculture and Agri-Food Canada, London, ON N5V 4T3, Canada; University of Western Ontario, London, Ontario, Canada. Electronic address: ed.topp@agr.gc.ca.
authors.forename: Edward
authors.initials: E
authors.lastname: Topp
mesh_terms: D000818:Animals; D003612:Dairying; D004352:Drug Resistance, Microbial / Q000235:genetics*; D005308:Fertilizers; D005798:Genes, Bacterial; D008372:Manure; D012987:Soil; D012988:Soil Microbiology; D014675:Vegetables
chemical_list: D005308:Fertilizers; D008372:Manure; D012987:Soil
keywords: Agricultural soil; Antibiotic resistance genes; Manure; Risk of exposure; Vegetables