Holley Richard A, Arrus Katia M, Ominski Kimberly H, Tenuta Mario, Blank Gregory
Department of Food Science, University of Manitoba, Winnipeg, MB, R3T 2N2 Canada.
J Environ Qual. 2006 May 31;35(4):1170-80. doi: 10.2134/jeq2005.0449. Print 2006 Jul-Aug.
Addition of animal manure to soil can provide opportunity for Salmonella contamination of soil, water, and food. This study examined how exposure of hog manure-treated loamy sand and clay soils to different simulated seasonal temperature sequences influenced the length of Salmonella survival. A six-strain cocktail of Salmonella serovars (Agona, Hadar, Heidelberg, Montevideo, Oranienburg, and Typhimurium) was added to yield 5 log cfu/g directly to about 5 kg of the two soils and moisture adjusted to 60 or 80% of field capacity (FC). Similarly, the Salmonella cocktail was mixed with fresh manure slurry from a hog nursery barn and the latter added to the two soils at 25 g/kg to achieve 5 log cfu/g Salmonella. Manure was mixed either throughout the soil or with the top kilogram of soil and the entire soil volume was adjusted to 60 or 80% FC. Soil treatments were stored 180 d at temperature sequences representing winter to summer (-18, 4, 10, 25 degrees C), spring to summer (4, 10, 25, 30 degrees C), or summer to winter (25, 10, 4, -18 degrees C) seasonal periods with each temperature step lasting 45 d. Samples for Salmonella recovery by direct plating or enrichment were taken at 0, 7, and 15 d post-inoculation and thereafter at 15-d intervals to 180 d. Salmonella numbers decreased during application to soil and the largest decreases occurred within the first week. Higher soil moisture, manure addition, and storage in the clay soil increased Salmonella survival. Salmonella survived longest (> or = 180 d) in both soils during summer-winter exposure but was not isolated after 160 d from loamy sand soil exposed to other seasonal treatments. For all but one treatment decimal reduction time (DRT45d) values calculated from the first 45 d after application were < or = 30 d and suggested that a 30-d delay between field application of manure in the spring or fall and use of the land would provide reasonable assurance that crop and animal contamination by Salmonella would be minimized.
向土壤中添加动物粪便会为沙门氏菌污染土壤、水和食物创造机会。本研究考察了经猪粪处理的壤质砂土和黏土在不同模拟季节性温度序列下暴露情况对沙门氏菌存活时长的影响。将六种血清型沙门氏菌（阿哥纳、哈达尔、海德堡、蒙得维的亚、奥兰宁堡和鼠伤寒）的混合菌液直接添加至约5千克这两种土壤中，使土壤中沙门氏菌含量达到5 log cfu/g，并将土壤湿度调整至田间持水量（FC）的60%或80%。同样，将沙门氏菌混合菌液与来自仔猪保育舍的新鲜粪水混合，然后按25克/千克的比例添加至这两种土壤中，使土壤中沙门氏菌含量达到5 log cfu/g。粪水要么与整个土壤混合，要么仅与表层1千克土壤混合，并将整个土壤体积的湿度调整至FC的60%或80%。土壤处理后的样品在代表冬夏（-18、4、10、25摄氏度）、春夏（4、10、25、30摄氏度）或夏秋（25、10、4、-18摄氏度）季节周期的温度序列下储存180天，每个温度阶段持续45天。在接种后0、7和15天以及之后每隔15天直至180天采集用于通过直接平板计数或富集培养来回收沙门氏菌的样品。在添加到土壤的过程中沙门氏菌数量减少，且最大降幅出现在第一周内。较高的土壤湿度、添加粪水以及在黏土中储存可提高沙门氏菌的存活率。在夏冬暴露期间，沙门氏菌在两种土壤中存活时间最长（≥180天），但在暴露于其他季节处理的壤质砂土中，160天后未再分离出沙门氏菌。对于除一种处理外的所有处理，在添加后前45天计算得出的十进制减少时间（DRT45d）值≤30天，这表明在春季或秋季田间施用粪水与土地使用之间间隔30天，将能合理保证沙门氏菌对作物和动物的污染降至最低。
