Virgnia Tech, Department of Food Science and Technology, 1230 Washington St, Blacksburg, VA 24061, USA.
Virgnia Tech, Department of Fisheries and Wildlife, 310 W Campus Dr, Blacksburg, VA 24061, USA.
J Food Prot. 2023 Mar;86(3):100042. doi: 10.1016/j.jfp.2023.100042. Epub 2023 Jan 13.
Campylobacter and pathogenic Escherichia coliillnesses have been attributed to the consumption of fresh produce. The leafy green, kale, is increasingly consumed raw. In comparison to other leafy greens, kale has a longer shelf-life. Due to the extended shelf-life of kale, it is warranted to examine the survival of pathogenic Campylobacter jejuni and E. coli O157:H7 inoculated on the surface of kale stored in a controlled environment at 4 ± 1.4°C, and average humidity of 95 ± 1.9% over a 23-day period. At predetermined time points (days 0, 1, 2, 3, 5, 7, 9, 11, 13, 15, 17, 19, and 21), inoculated kale was destructively sampled and the surviving bacteria determined by serial dilution and plating onto Tryptic soy agar, Charcoal cefoperozone deoxycholate agar, and Eosin methylene blue for total aerobic bacteria, C. jejuni, and E. coli O157:H7, respectively. Enrichment and PCR were used for detection when pathogens were not detected using serial dilution and plating. Aerobic heterotrophic bacteria increased over the 23-day period, in contrast, significant declines in the inoculated pathogens were observed. Inoculated E. coli O157:H7 survived longer on kale (up to 19 d); in comparison, C. jejuni was undetectable by day 13 using enrichment and PCR or plating. In conclusion, C. jejuni and E. coli O157:H7 declined on fresh kale over time when held at refrigerated temperatures but were still detected during the majority of the time when the kale would likely still be considered edible by consumers.
弯曲杆菌和致病性大肠杆菌疾病已归因于食用新鲜农产品。叶状绿色的羽衣甘蓝越来越多地被生食。与其他叶状绿色蔬菜相比，羽衣甘蓝的保质期更长。由于羽衣甘蓝的保质期延长，因此有必要检查在 4 ± 1.4°C 的受控环境下储存的羽衣甘蓝表面接种的致病性空肠弯曲杆菌和大肠杆菌 O157:H7 的存活情况，平均湿度为 95 ± 1.9%，持续 23 天。在预定的时间点（第 0、1、2、3、5、7、9、11、13、15、17、19 和 21 天），对接种的羽衣甘蓝进行破坏性采样，并通过连续稀释和在胰蛋白酶大豆琼脂、木炭头孢泊肟去氧胆酸盐琼脂和曙红亚甲基蓝上划线来确定存活的细菌，分别用于总需氧细菌、空肠弯曲杆菌和大肠杆菌 O157:H7。当使用连续稀释和划线未检测到病原体时，使用富集和 PCR 进行检测。在 23 天的时间里，好氧异养细菌增加，而接种的病原体则明显减少。接种的大肠杆菌 O157:H7 在羽衣甘蓝上存活时间更长（长达 19 天）；相比之下，使用富集和 PCR 或划线，空肠弯曲杆菌在第 13 天无法检测到。总之，在冷藏温度下，新鲜羽衣甘蓝上的空肠弯曲杆菌和大肠杆菌 O157:H7 随时间推移而减少，但在大多数时间内仍能检测到，消费者可能仍会认为羽衣甘蓝可食用。
