Brar Pardeepinder K, Strawn Laura K, Danyluk Michelle D
Department of Food Science and Human Nutrition, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850, USA.
Department of Food Science and Technology, Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, 33446 Research Drive, Painter, Virginia 23420, USA.
J Food Prot. 2016 Mar;79(3):352-60. doi: 10.4315/0362-028X.JFP-15-365.
In-shell pecan samples (500 g) were collected over four harvest seasons (2010 to 2014) from seven pecan shelling facilities located in five U.S. states. Four varieties of pecans were analyzed: Mexican Improved, Native Seedlings, Southern Improved, and Western Improved. Pecan samples (100 g) were sent to a third party laboratory for initial Salmonella screening. When a sample was positive for Salmonella, the pathogen level was determined by the most-probable-number (MPN) method (25, 2.5, and 0.25 g). Two sample preparation strategies were used for the MPN analysis, and both strategies were combined for the reported MPN values. Forty-four (0.95%) of 4,641 in-shell pecan samples were positive for Salmonella during initial screening; prevalence by year was 0.47 to 1.4%. Prevalence was not significantly different between varieties: Mexican Improved, 1.2%; Native/Seedling, 0.99%; Southern Improved, 0.97%; and Western Improved, 0.75%. Salmonella was not isolated from 31 of 44 samples upon retesting during MPN analysis (<0.47 MPN/100 g). When Salmonella was detected, the levels were 0.47 to 39 MPN/100 g, with a mean of 2.4 MPN/100 g. Thirty-one Salmonella serotypes were obtained from 42 Salmonella-positive pecan samples; Enteritidis was the most common (12% of samples) followed by Javiana (9%) and Braenderup (7%). All Salmonella Enteritidis isolates were phage type 8. Pulsed-field gel electrophoresis analysis (XbaI) revealed within-serotype diversity, indicating introduction of contamination from a variety of sources. Most (64%) of the isolates were resistant to streptomycin or tetracycline, and 13% were resistant to three or more antibiotics. Salmonella prevalence and level on in-shell pecans is comparable to that on other nuts.
在2010年至2014年的四个收获季节，从美国五个州的七个山核桃脱壳设施收集了带壳山核桃样本（500克）。分析了四种山核桃品种：墨西哥改良种、本地实生苗种、南方改良种和西方改良种。将山核桃样本（100克）送至第三方实验室进行沙门氏菌初步筛查。当样本沙门氏菌检测呈阳性时，通过最大可能数（MPN）法（25克、2.5克和0.25克）确定病原体水平。MPN分析采用了两种样本制备策略，报告的MPN值为两种策略的综合结果。在初步筛查中，4641个带壳山核桃样本中有44个（0.95%）沙门氏菌检测呈阳性；各年份的患病率为0.47%至1.4%。不同品种之间的患病率无显著差异：墨西哥改良种为1.2%；本地/实生苗种为0.99%；南方改良种为0.97%；西方改良种为0.75%。在MPN分析的复测中，44个样本中有31个未分离出沙门氏菌（<0.47 MPN/100克）。当检测到沙门氏菌时，其水平为0.47至39 MPN/100克，平均为2.4 MPN/100克。从42个沙门氏菌阳性山核桃样本中获得了31种沙门氏菌血清型；肠炎沙门氏菌最为常见（占样本的12%），其次是贾维亚沙门氏菌（9%）和布伦德鲁普沙门氏菌（7%）。所有肠炎沙门氏菌分离株均为8型噬菌体。脉冲场凝胶电泳分析（XbaI）显示血清型内存在多样性，表明污染来自多种来源。大多数（64%）分离株对链霉素或四环素耐药，13%对三种或更多抗生素耐药。带壳山核桃上沙门氏菌的患病率和水平与其他坚果相当。
