Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. FDA, Laurel, MD, USA.
Office of Analytics and Outreach, Center for Food Safety and Applied Nutrition, U.S. FDA, College Park, MD, USA.
J Food Prot. 2024 Jun;87(6):100290. doi: 10.1016/j.jfp.2024.100290. Epub 2024 May 1.
Two recent outbreaks of listeriosis have been linked to the consumption of enoki mushrooms. After the first outbreak, import sampling by the U.S. FDA identified that 43% of the samples evaluated were positive for Listeria monocytogenes (Lm). These observations raised questions about the potential sources of Lm contamination of enoki mushrooms. One potential source of contamination is during enoki mushroom cultivation, as growing conditions are comparatively cool and moist to induce mushroom germination, to which Lm is well adapted. Two varieties of enoki mushrooms were evaluated to determine the potential for Lm to contaminate enoki cultures when introduced at various points during cultivation (inoculation, scraping, pinning, and collaring). The results of two trials showed that Lm established contamination and grew to similar levels in the substrate regardless of when Lm was introduced and, with one exception, did not alter the rate of mushroom generation to below the control. Enumeration of Lm in enoki mushroom cultures at harvest found an average contamination of 10 cfu/g, though the results were variable. Refrigerated storage for six weeks was found to result in an increase in Lm. Additionally, no statistically significant difference in the levels of Lm was observed based on proximity to the substrate, though levels of Lm in the different enoki samples correlated with levels of Lm in the substrate at harvest, but not at scraping. The ability of Lm to grow independently in the media used to culture enoki was assessed, and Lm was found to be unable to grow but could sporadically survive in Masters Mix. No growth of Lm was observed in potato dextrose broth, though growth could occur on the agar. Overall, the data indicate a high potential for the establishment of Lm contamination at any point during enoki cultivation to result in Lm-contaminated mushrooms. These data indicate a need for active control mechanisms to prevent the introduction of Lm to enoki cultures.
最近爆发的两起李斯特菌病疫情与食用金针菇有关。第一次疫情爆发后，美国 FDA 的进口抽样调查发现，评估的样本中有 43%呈李斯特菌阳性（Lm）。这些观察结果引发了人们对金针菇 Lm 污染潜在来源的质疑。一种潜在的污染来源是在金针菇种植过程中，由于种植条件相对较凉爽和潮湿，以诱导蘑菇发芽，而李斯特菌非常适应这种环境。评估了两种金针菇品种，以确定在种植过程中不同时间（接种、刮削、钉住和套圈）引入 Lm 时，金针菇培养物可能受到 Lm 污染的情况。两项试验的结果表明，无论何时引入 Lm，Lm 都会在基质中建立污染并生长到相似水平，除了一个例外，不会改变蘑菇生成速度低于对照。在收获时对金针菇培养物中的 Lm 进行计数，发现平均污染水平为 10cfu/g，但结果存在差异。冷藏保存六周会导致 Lm 增加。此外，尽管 Lm 水平与基质中 Lm 水平相关，但基于与基质的接近程度，未观察到 Lm 水平存在统计学差异。评估了 Lm 在用于培养金针菇的培养基中独立生长的能力，发现 Lm 无法生长，但可以在 Masters Mix 中偶尔存活。在土豆葡萄糖肉汤中未观察到 Lm 生长，但在琼脂上可以生长。总体而言，这些数据表明，在金针菇种植过程中的任何时间，Lm 污染的建立都有很高的可能性导致 Lm 污染的蘑菇。这些数据表明需要采取积极的控制机制来防止 Lm 引入金针菇培养物。
