title: Impact of pre-application treatment on municipal sludge composition, soil dynamics of antibiotic resistance genes, and abundance of antibiotic-resistance genes on vegetables at harvest.
abstract: In many jurisdictions sludge recovered from the sewage treatment process is a valued fertilizer for crop production. Pre-treatment of sewage sludge prior to land application offers the potential to abate enteric microorganisms that carry genes conferring resistance to antibiotics. Pre-treatment practices that accomplish this should have the desirable effect of reducing the risk of contamination of crops or adjacent water with antibiotic resistance genes carried in these materials. In the present study, we obtained municipal sludge that had been subjected to one of five treatments. There were, anaerobic-digestion or aerobic-digestion, in both instances with and without dewatering; and heat-treatment and pelletization. Each of the five types of biosolids was applied to an agricultural field at commercial rates, following which lettuce, carrots and radishes were planted. Based on qPCR, the estimated antibiotic gene loading rates were comparable with each of the five biosolids. However, the gene abundance in soil following application of the pelletized biosolids was anomalously lower than expected. Following application, the abundance of antibiotic resistance genes decreased in a generally coherent fashion, except sul1 which increased in abundance during the growing season in the soil fertilized with pelletized biosolids. Based on qPCR and high throughput sequencing evidence for transfer of antibiotic resistance genes from the biosolids to the vegetables at harvest was weak. Clostridia were more abundant in soils receiving any of the biosolids except the pelletized. Overall, the behavior of antibiotic resistance genes in soils receiving aerobically or anaerobically-digested biosolids was consistent and coherent with previous studies. However, dynamics of antibiotic resistance genes in soils receiving the heat treated pelletized biosolids were very different, and the underlying mechanisms merit investigation.
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: Calvin Ho-Fung
authors.initials: CH
authors.lastname: Lau
authors.affiliation: Graduate School at Shenzhen, Tsinghua University, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Li
authors.affiliation: Environmental Biotechnology Laboratory, The University of Hong Kong.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: Yuan-Ching
authors.initials: YC
authors.lastname: Tien
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Scott
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: Roger
authors.initials: R
authors.lastname: Murray
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: Lyne
authors.initials: L
authors.lastname: Sabourin
authors.affiliation: Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada.
authors.forename: David R
authors.initials: DR
authors.lastname: Lapen
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Duenk
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada; Department of Biology, 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: D000383:Agriculture / Q000379:methods; D000069599:Crop Production / Q000706:statistics & numerical data; D018556:Crops, Agricultural / Q000254:growth & development*; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004784:Environmental Monitoring; D005308:Fertilizers; D012987:Soil; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D005308:Fertilizers; D012987:Soil; D012989:Soil Pollutants
keywords: Agriculture; Antimicrobial resistance; Biosolids; Soil quality; Vegetables