Racine Jason, Nerney Alexandra, Kilgore Samantha, Waters Tim, Critzer Faith, Harris Linda J, Reitz Stuart, Waite-Cusic Joy
Department of Food Science and Technology, College of Agricultural Sciences, Oregon State University, Corvallis, OR 97331, USA.
Franklin County Extension, College of Agricultural, Human, and Natural Resource Sciences, Washington State University, Pasco, WA 99301, USA.
J Food Prot. 2024 Dec;87(12):100373. doi: 10.1016/j.jfp.2024.100373. Epub 2024 Oct 5.
Contaminated agricultural water has been implicated in produce-associated outbreaks, including dry bulb onions (Allium cepa). This study was designed to quantify risks associated with contaminated water used to prepare crop protection sprays applied immediately before the onset of field curing of dry bulb onions. Laboratory experiments determining the behavior of Salmonella and Escherichia coli in crop protection chemical solutions were performed to guide selection for field use. Field trials were conducted (2022, 2023) in eastern Oregon (Treasure Valley) using two onion cultivars ('Red Wing' and 'Cometa') inoculated with a rifampicin-resistant E. coli cocktail (3-4 log CFU/100 mL) suspended in fungicide solution or clay suspension, and applied with a backpack sprayer at the end of the growing season. Onions were sampled through the next 4 weeks of field curing and after 1 and 4-5 mos of postharvest storage. In 2022, onions were initially contaminated at a maximum cell density of 48 MPN/onion (Geometric mean (GM): 3.7 MPN/onion). At the end of curing, a single onion (out of 320) tested positive at 2 MPN/onion. In 2022, E. coli was not detected during postharvest storage (n = 160). In 2023, the application of contaminated sprays resulted in a maximum contamination of 275 MPN/onion (GM: 8.6 MPN/onion). At the end of the 2023 curing period, three out of 320 onions (0.9%) had detectable levels of E. coli (1-2 MPN/onion). Three 'Cometa' onions from the same plot that were treated with fungicide were positive for E. coli after 5 months of postharvest storage (2, 11, and 83 MPN/onion). These field trials indicate field curing conditions in the Treasure Valley help mitigate risks associated with contaminated water used for applying crop protection sprays. E. coli was detected on a small percentage of onions at low cell density after curing. The single onion with elevated E. coli populations after postharvest storage had internal damage characteristic of bacterial rot.
受污染的农业用水已被认为与包括干球洋葱（葱属）在内的农产品相关疫情有关。本研究旨在量化与在干球洋葱田间晾晒开始前立即用于配制作物保护喷雾的受污染水相关的风险。进行了实验室实验以确定沙门氏菌和大肠杆菌在作物保护化学溶液中的行为，以指导田间使用的选择。2022年和2023年在俄勒冈州东部（宝藏谷）进行了田间试验，使用两个洋葱品种（“红翼”和“科梅塔”），接种了悬浮在杀菌剂溶液或粘土悬浮液中的耐利福平大肠杆菌混合菌液（3 - 4 log CFU/100 mL），并在生长季节结束时用背负式喷雾器进行喷洒。在接下来的4周田间晾晒期间以及收获后1个月和4 - 5个月后对洋葱进行采样。2022年，洋葱最初的污染最大细胞密度为48 MPN/洋葱（几何平均值（GM）：3.7 MPN/洋葱）。在晾晒结束时，320个洋葱中有1个检测呈阳性，为2 MPN/洋葱。2022年，收获后储存期间未检测到大肠杆菌（n = 160）。2023年，受污染喷雾的施用导致最大污染为275 MPN/洋葱（GM：8.6 MPN/洋葱）。在2023年晾晒期结束时，320个洋葱中有3个（0.9%）检测到大肠杆菌水平（1 - 2 MPN/洋葱）。来自同一地块用杀菌剂处理的3个“科梅塔”洋葱在收获后储存5个月后大肠杆菌检测呈阳性（2、11和83 MPN/洋葱）。这些田间试验表明，宝藏谷的田间晾晒条件有助于降低与用于施用作物保护喷雾的受污染水相关的风险。晾晒后，在一小部分洋葱上检测到低细胞密度的大肠杆菌。收获后储存后大肠杆菌数量升高的单个洋葱有细菌性腐烂的内部损伤特征。
