Detection of Cyclospora cayetanensis on bagged pre-cut salad mixes within their shelf-life and after sell by date by the US food and drug administration validated method
Detection of Cyclospora cayetanensis on bagged pre-cut salad mixes within their shelf-life and after sell by date by the US food and drug administration validated method
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DOI：
10.1016/j.fm.2021.103802
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发表时间：
2021-04-05
影响因子：
5.3
通讯作者：
Shipley, Alicia
中科院分区：
文献类型：
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作者：
Almeria, Sonia;Shipley, Alicia
近期，美国的环孢子虫病暴发与食用多种含有生菜和/或卷心莴苣、胡萝卜和/或紫甘蓝的沙拉有关。《细菌学分析手册》（BAM）第19b章的方法已被验证可用于检测胡萝卜、甘蓝和生菜中的环孢子虫，但此前尚未在即食（RTE）混合沙拉中进行评估。此外，可用于追溯调查的样本有时是状况不佳的剩余物。本研究评估了已验证的BAM方法在两种不同的即食混合沙拉（混合沙拉1：生菜和卷心莴苣、胡萝卜和紫甘蓝；混合沙拉2：生菜和卷心莴苣、胡萝卜、紫甘蓝、萝卜和豌豆荚）在良好状态以及保质期过后检测环孢子虫的情况。将单个样本（25克）分别接种5个和200个环孢子虫卵囊。未接种的农产品用作阴性对照。该方法包括农产品的清洗、环孢子虫DNA的浓缩和提取以及环孢子虫18S rRNA基因的分子检测。在新鲜的以及保质期过后的混合沙拉中都能检测到少至5个卵囊。所有未接种的样本均为阴性，两种沙拉类型中接种200个卵囊的所有样本均为阳性。在接种200个卵囊的样本中，新鲜混合沙拉1中环孢子虫18S rRNA的平均CT值明显高于新鲜混合沙拉2；保质期过后的沙拉与其相应的新鲜混合沙拉相比，CT值明显更高（p < 0.05）。总之，BAM方法即使在即食混合沙拉保质期过后也能够检测到少至5个卵囊。然而，观察到的检测差异凸显了在未来疫情调查之前，评估已验证的环孢子虫检测方法在不同食品基质和条件下性能的重要性。
Recently, outbreaks of Cyclospora cayetanensis in the U.S. were linked to the consumption of a variety of salads containing romaine and/or iceberg lettuce, carrots and/or red cabbage. The Bacteriological Analytical Manual (BAM) Chapter 19b method was validated for the detection of C. cayetanensis in carrots, cabbage and romaine lettuce, but has not been previously evaluated in ready-to-eat (RTE) salad mixes. In addition, the only samples available for traceback investigations are sometimes leftovers in bad conditions. This study evaluated the vali-dated BAM method for detection of C. cayetanensis in two different RTE mixed salads (mix 1: romaine and iceberg lettuces, carrots, and red cabbage and mix 2: romaine and iceberg lettuces, carrots, red cabbage, radish, and pea pods) in good condition and after their sell by date. Individual samples (25 g) were seeded with five and 200 C. cayetanensis oocysts. Unseeded produce was used as negative control. The method included washing of the produce, concentration and extraction of C. cayetanensis DNA and molecular detection of C. cayetanensis 18 S rRNA gene. As few as five oocysts were detected in both fresh and after sell by date mix salads. All unseeded samples were negative, and all samples of both salad types seeded with 200 oocysts were positive. In samples seeded with 200 oocysts, average 18 S rRNA C. cayetanensis CT values were significantly higher in fresh salad mix 1 compared to fresh salad mix 2; CT values were significantly higher in the after sell by date salads compared to their respective fresh mixes (p < 0.05). In conclusion, the BAM method was able to detect as few as five oocysts even in after sell by date RTE mix salads. However, the differences in detection observed, highlight the importance of evaluating the performance of the validated C. cayetanensis detection method in different food matrices and conditions, in advance for future outbreak investigations.