Microbial Safety Division, Department of Agri-Food Safety, National Academy of Agricultural Science, Rural Development Administration, Suwon 441-707, South Korea.
J Food Prot. 2012 Jul;75(7):1213-8. doi: 10.4315/0362-028X.JFP-11-420.
Sample preparation methods (pummeling, pulsifying, sonication, and shaking by hand) were compared for achieving maximum recovery of foodborne pathogens from iceberg lettuce, perilla leaves, cucumber, green pepper, and cherry tomato. Antimicrobial and dehydration effects also were examined to investigate causes of poor recovery of pathogens. Each produce type was inoculated with Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus at 6.0 log CFU/cm(2), and samples were prepared using the four methods. Bacterial populations recovered from the five types of produce were significantly different (P < 0.05) according to sample preparation methods and produce type. The bacterial populations recovered from pummeled and pulsified samples were higher (P < 0.05) than those recovered from sonicated and hand-shaken samples, except for cherry tomato. The number of bacteria recovered from produce was reduced (P < 0.05) from that of the inoculum by 0.16 to 2.69 log CFU/cm(2). Although extracts of iceberg lettuce, perilla leaves, cucumber, and green pepper had no antimicrobial activity, the populations of E. coli O157:H7, Salmonella Typhimurium, B. cereus, and L. monocytogenes in cherry tomato extract were slightly reduced after these treatments (P < 0.05). The pathogen populations on perilla leaves and cherry tomatoes decreased by >2 log CFU/cm(2) after exposure to 40% relative humidity for 1 h. No reduction was observed when the five pathogens were exposed to 90% relative humidity. These data suggest that pummeling and pulsifying are optimal sample preparation methods for detection of microorganisms. Acidic produce such as cherry tomato should be treated with a method that does not cause sample breakdown so that acid stress on the bacteria can be minimized. Dehydration stress also affects recovery of pathogens from produce.
比较了研磨、脉动、超声和手动摇晃等样品制备方法，以实现从冰山生菜、紫苏叶、黄瓜、青椒和樱桃番茄中最大程度回收食源性病原体。还研究了抗菌和脱水作用，以调查导致病原体回收率低的原因。将大肠杆菌 O157:H7、鼠伤寒沙门氏菌、单核细胞增生李斯特菌、金黄色葡萄球菌和蜡样芽孢杆菌分别以 6.0 log CFU/cm(2)的浓度接种到每种作物类型上，然后使用这四种方法进行样品制备。根据样品制备方法和作物类型，从五种作物中回收的细菌种群差异显著（P < 0.05）。与超声和手动摇晃处理的样品相比，经研磨和脉动处理的样品中回收的细菌种群更高（P < 0.05），但樱桃番茄除外。从作物中回收的细菌数量比接种物减少了 0.16 至 2.69 log CFU/cm(2)（P < 0.05）。尽管冰山生菜、紫苏叶、黄瓜和青椒的提取物没有抗菌活性，但樱桃番茄提取物中大肠杆菌 O157:H7、鼠伤寒沙门氏菌、蜡样芽孢杆菌和单核细胞增生李斯特菌的数量在经过这些处理后略有减少（P < 0.05）。在 40%相对湿度下暴露 1 小时后，紫苏叶和樱桃番茄上的病原体种群减少了 >2 log CFU/cm(2)。当五种病原体暴露于 90%相对湿度时，没有观察到减少。这些数据表明，研磨和脉动是检测微生物的最佳样品制备方法。应采用不会导致样品分解的方法处理酸性作物，如樱桃番茄，以尽量减少细菌的酸应激。脱水应激也会影响从农产品中回收病原体。
