United States Department of Agriculture, Agricultural Research Service, Northeast Area, Environmental Microbial and Food Safety Laboratory, Beltsville MD, United States of America.
Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, MD, United States of America.
PLoS One. 2020 Mar 17;15(3):e0229365. doi: 10.1371/journal.pone.0229365. eCollection 2020.
Irrigation water contaminated with Salmonella enterica and Listeria monocytogenes may provide a route of contamination of raw or minimally processed fruits and vegetables. While previous work has surveyed specific and singular types of agricultural irrigation water for bacterial pathogens, few studies have simultaneously surveyed different water sources repeatedly over an extended period of time. This study quantified S. enterica and L. monocytogenes levels (MPN/L) at 6 sites, including river waters: tidal freshwater river (MA04, n = 34), non-tidal freshwater river, (MA05, n = 32), one reclaimed water holding pond (MA06, n = 25), two pond water sites (MA10, n = 35; MA11, n = 34), and one produce wash water site (MA12, n = 10) from September 2016-October 2018. Overall, 50% (84/168) and 31% (53/170) of sampling events recovered S. enterica and L. monocytogenes, respectively. Results showed that river waters supported significantly (p < 0.05) greater levels of S. enterica than pond or reclaimed waters. The non-tidal river water sites (MA05) with the lowest water temperature supported significantly greater level of L. monocytogenes compared to all other sites; L. monocytogenes levels were also lower in winter and spring compared to summer seasons. Filtering 10 L of water through a modified Moore swab (MMS) was 43.5 (Odds ratio, p < 0.001) and 25.5 (p < 0.001) times more likely to recover S. enterica than filtering 1 L and 0.1 L, respectively; filtering 10 L was 4.8 (p < 0.05) and 3.9 (p < 0.05) times more likely to recover L. monocytogenes than 1L and 0.1 L, respectively. Work presented here shows that S. enterica and L. monocytogenes levels are higher in river waters compared to pond or reclaimed waters in the Mid-Atlantic region of the U.S., and quantitatively shows that analyzing 10 L water is more likely recover pathogens than smaller samples of environmental waters.
受沙门氏菌和李斯特菌污染的灌溉水可能会污染生的或经过最低限度加工的水果和蔬菜。虽然之前的工作已经调查了农业灌溉水中特定和单一类型的细菌病原体，但很少有研究在较长时间内同时重复调查不同的水源。本研究量化了 6 个地点的沙门氏菌和李斯特菌水平（MPN/L），包括河流：潮汐淡水河（MA04，n = 34）、非潮汐淡水河（MA05，n = 32）、一个再生水蓄水塘（MA06，n = 25）、两个池塘水地点（MA10，n = 35；MA11，n = 34）和一个农产品清洗水地点（MA12，n = 10），时间为 2016 年 9 月至 2018 年 10 月。总体而言，50%（84/168）和 31%（53/170）的采样事件分别回收了沙门氏菌和李斯特菌。结果表明，与池塘或再生水相比，河流水支持的沙门氏菌水平显著更高（p < 0.05）。水温最低的非潮汐河流水地点（MA05）与所有其他地点相比，李斯特菌水平显著更高；与夏季相比，冬季和春季的李斯特菌水平也较低。用改良的 Moore 拭子（MMS）过滤 10 L 水比过滤 1 L 和 0.1 L 分别回收沙门氏菌的可能性高 43.5（优势比，p < 0.001）和 25.5（p < 0.001）倍；过滤 10 L 比过滤 1 L 和 0.1 L 分别回收李斯特菌的可能性高 4.8（p < 0.05）和 3.9（p < 0.05）倍。这里介绍的工作表明，与美国中大西洋地区的池塘或再生水相比，河流水中的沙门氏菌和李斯特菌水平更高，并定量表明，分析 10 L 水比分析较小的环境水样更有可能回收病原体。
