title: Impact of fertilizing with raw or anaerobically digested sewage sludge on the abundance of antibiotic-resistant coliforms, antibiotic resistance genes, and pathogenic bacteria in soil and on vegetables at harvest.
abstract: The consumption of crops fertilized with human waste represents a potential route of exposure to antibiotic-resistant fecal bacteria. The present study evaluated the abundance of bacteria and antibiotic resistance genes by using both culture-dependent and molecular methods. Various vegetables (lettuce, carrots, radish, and tomatoes) were sown into field plots fertilized inorganically or with class B biosolids or untreated municipal sewage sludge and harvested when of marketable quality. Analysis of viable pathogenic bacteria or antibiotic-resistant coliform bacteria by plate counts did not reveal significant treatment effects of fertilization with class B biosolids or untreated sewage sludge on the vegetables. Numerous targeted genes associated with antibiotic resistance and mobile genetic elements were detected by PCR in soil and on vegetables at harvest from plots that received no organic amendment. However, in the season of application, vegetables harvested from plots treated with either material carried gene targets not detected in the absence of amendment. Several gene targets evaluated by using quantitative PCR (qPCR) were considerably more abundant on vegetables harvested from sewage sludge-treated plots than on vegetables from control plots in the season of application, whereas vegetables harvested the following year revealed no treatment effect. Overall, the results of the present study suggest that producing vegetable crops in ground fertilized with human waste without appropriate delay or pretreatment will result in an additional burden of antibiotic resistance genes on harvested crops. Managing human exposure to antibiotic resistance genes carried in human waste must be undertaken through judicious agricultural practice.
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: Teddie O
authors.initials: TO
authors.lastname: Rahube
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: Romain
authors.initials: R
authors.lastname: Marti
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: Yuan-Ching
authors.initials: YC
authors.lastname: Tien
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, London, Ontario, Canada.
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhang
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, Ottawa, Ontario, Canada.
authors.forename: David R
authors.initials: DR
authors.lastname: Lapen
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario, Canada Department of Biology, University of Western Ontario, London, Ontario, Canada ed.topp@agr.gc.ca.
authors.forename: Edward
authors.initials: E
authors.lastname: Topp
mesh_terms: D000383:Agriculture; D000693:Anaerobiosis; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D005243:Feces / Q000382:microbiology; D005308:Fertilizers / Q000009:adverse effects / Q000382:microbiology*; D006801:Humans; D012722:Sewage / Q000382:microbiology*; D012988:Soil Microbiology; D014675:Vegetables / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D005308:Fertilizers; D012722:Sewage