title: The growing season, but not the farming system, is a food safety risk determinant for leafy greens in the mid-Atlantic region of the United States.
abstract: Small- and medium-size farms in the mid-Atlantic region of the United States use varied agricultural practices to produce leafy greens during spring and fall, but the impact of preharvest practices on food safety risk remains unclear. To assess farm-level risk factors, bacterial indicators, Salmonella enterica, and Shiga toxin-producing Escherichia coli (STEC) from 32 organic and conventional farms were analyzed. A total of 577 leafy greens, irrigation water, compost, field soil, and pond sediment samples were collected. Salmonella was recovered from 2.2% of leafy greens (n = 369) and 7.7% of sediment (n = 13) samples. There was an association between Salmonella recovery and growing season (fall versus spring) (P = 0.006) but not farming system (organic or conventional) (P = 0.920) or region (P = 0.991). No STEC was isolated. In all, 10% of samples were positive for E. coli: 6% of leafy greens, 18% of irrigation water, 10% of soil, 38% of sediment, and 27% of compost samples. Farming system was not a significant factor for levels of E. coli or aerobic mesophiles on leafy greens but was a significant factor for total coliforms (TC) (P < 0.001), with higher counts from organic farm samples. Growing season was a factor for aerobic mesophiles on leafy greens (P = 0.004), with higher levels in fall than in spring. Water source was a factor for all indicator bacteria (P < 0.001), and end-of-line groundwater had marginally higher TC counts than source samples (P = 0.059). Overall, the data suggest that seasonal events, weather conditions, and proximity of compost piles might be important factors contributing to microbial contamination on farms growing leafy greens.
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, Lower Eastern Shore Research and Education Center, Salisbury, Maryland, USA.
authors.forename: Sasha C
authors.initials: SC
authors.lastname: Marine
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland, USA.
authors.forename: Sivaranjani
authors.initials: S
authors.lastname: Pagadala
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland, USA.
authors.forename: Donna M
authors.initials: DM
authors.lastname: Pahl
authors.affiliation: Rutgers Cooperative Extension of Mercer County, Rutgers University, Trenton, New Jersey, USA.
authors.forename: Meredith V
authors.initials: MV
authors.lastname: Melendez
authors.affiliation: Rutgers Cooperative Extension of Cumberland County, Rutgers University, Millville, New Jersey, USA.
authors.forename: Wesley L
authors.initials: WL
authors.lastname: Kline
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, USA.
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Oni
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Walsh
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, Lower Eastern Shore Research and Education Center, Salisbury, Maryland, USA University of Delaware, Carvel Research and Education Center, Georgetown, Delaware, USA.
authors.forename: Kathryne L
authors.initials: KL
authors.lastname: Everts
authors.affiliation: Center for Food Safety and Security Systems, University of Maryland, College Park, Maryland, USA Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Buchanan
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland, USA Center for Food Safety and Security Systems, University of Maryland, College Park, Maryland, USA smicall@umd.edu.
authors.forename: Shirley A
authors.initials: SA
authors.lastname: Micallef
mesh_terms: D000383:Agriculture / Q000379:methods*; D058491:Bacterial Load; D004755:Enterobacteriaceae / Q000302:isolation & purification; D059022:Food Safety; D008873:Mid-Atlantic Region; D018570:Risk Assessment; D019779:Salmonella enterica / Q000302:isolation & purification*; D012621:Seasons; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification*; D014675:Vegetables / Q000382:microbiology*