Department of Population Health & Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA.
Department of Horticulture and Landscape Architecture College of Agricultural Sciences, Colorado State University, USA.
Int J Food Microbiol. 2021 Jun 2;347:109196. doi: 10.1016/j.ijfoodmicro.2021.109196. Epub 2021 Apr 14.
Due to the recent outbreaks of Salmonella and Escherichia coli in fresh produce in the United States, the transfer of foodborne pathogens between animal feeding operations and fresh produce continues to be a considerable risk. The purpose of this study was to determine if the establishment of a vegetation barrier (VB) on small-scale sustainable farms could prevent the transmission of Salmonella and E. coli to nearby fresh produce fields. A 5-layer VB (31 × 49 m) was constructed between a dairy farm, a poultry farm, and a nearby produce field. Fresh produce (i.e., romaine lettuce and tomato), animal feces, and environmental (i.e., air, soil, and barrier) samples were collected for 15 months from 2018 to 2019. Four replicates of soil and fresh produce samples were taken from three plots located 10 m, 61 m, and 122 m away from the respective animal locations and processed for Salmonella and E. coli. Air and vegetative strip samples were sampled at 15-day intervals. Multiple colonies were processed from each positive sample, and a total of 143 positive Salmonella (n = 15) and E. coli (n = 128) isolates were retrieved from the soil, produce, air, and fecal samples. Interestingly, 18.2% of the Salmonella and E. coli isolates (n = 26) were recovered from fresh produce (n = 9) samples. Surprisingly, Salmonella isolates (n = 9) were only found in fecal (n = 3) samples collected from the dairy pasture. Data analysis suggests that the VB is an effective tool at reducing the transmission of E. coli and Salmonella from animal farms to fresh produce fields. However, based on phenotypic and genotypic testing, it is clear that fecal samples from animal farms are not the only source of pathogen contamination. This indicates that the environment (e.g., soil and wind), as well as the initial setup of the farm (e.g., proximity to service roads and produce plot placement), can contribute to the contamination of fresh produce. Our study recommends the need for more effective bioremediation and prevention control measures to use in conjunction with VBs to reduce pathogen transmission.
由于美国新鲜农产品中沙门氏菌和大肠杆菌的近期爆发，食源性病原体在动物饲养场和新鲜农产品之间的转移仍然是一个相当大的风险。本研究的目的是确定在小规模可持续农场建立植被屏障 (VB) 是否可以防止沙门氏菌和大肠杆菌传播到附近的新鲜农产品田地。在奶牛场、家禽场和附近的农产品田地之间建造了一个 5 层 VB（31×49m）。从 2018 年到 2019 年，共收集了 15 个月的新鲜农产品（即罗马生菜和番茄）、动物粪便和环境（即空气、土壤和屏障）样本。从距离各自动物位置 10m、61m 和 122m 的三个地块中采集了四份土壤和新鲜农产品样本，并对沙门氏菌和大肠杆菌进行了处理。空气和植被带样本每 15 天采样一次。从每个阳性样本中处理了多个菌落，从土壤、农产品、空气和粪便样本中总共回收了 143 个阳性沙门氏菌（n=15）和大肠杆菌（n=128）分离株。有趣的是，18.2%的沙门氏菌和大肠杆菌分离株（n=26）是从新鲜农产品（n=9）样本中回收的。令人惊讶的是，仅从奶牛场牧场采集的粪便（n=3）样本中发现了沙门氏菌分离株（n=9）。数据分析表明，VB 是一种有效工具，可以减少动物农场到新鲜农产品田地的大肠杆菌和沙门氏菌的传播。然而，根据表型和基因型测试，很明显，动物农场的粪便样本并不是病原体污染的唯一来源。这表明环境（例如土壤和风向）以及农场的初始设置（例如靠近服务道路和农产品地块的位置）可能导致新鲜农产品受到污染。我们的研究建议需要采取更有效的生物修复和预防控制措施，与 VB 一起使用，以减少病原体的传播。
