An effective environmental sampling method involves the use of a transport/neutralizing broth with the ability to neutralize sanitizer residues that are collected during sampling and to maintain viability of stressed Listeria monocytogenes (Lm) cells. We applied Lm onto stainless steel surfaces and then subjected Lm to desiccation stress for 16–18 h at room temperature (RT, 21–24 °C). This was followed by the subsequent application of Whisper™ V, a quaternary ammonium compound (QAC)-based sanitizer, diluted to 400 ppm and 8000 ppm of active quat, for 6 h. We then sampled Lm with sponges pre-moistened in three transport broths, Dey/Engley (D/E) broth, Letheen broth and HiCap™ broth, to generate environmental samples that contained sanitizer residues and low levels of stressed Lm, which were subsequently analyzed by an enrichment-based method. This scheme conformed with validation guidelines of AOAC International by using 20 environmental test portions per broth that contained low levels of Lm such that not all test portions were positive (i.e., fractional positive). We showed that D/E broth, Letheen broth and HiCap™ broth performed similarly when no quat or 400 ppm of quat was applied to the Lm contaminating stainless steel surfaces. However, when 8000 ppm of quat was applied, Letheen broth did not effectively neutralize the QAC in the samples. These comparisons were performed on samples stored under three conditions after collection to replicate scenarios of sample transport, RT for 2 h, 4 °C for 24 h and 4 °C for 72 h. Comparisons under the three different scenarios generally reached the same conclusions. In addition, we further demonstrated that storing Letheen and HiCap™ broths at RT for two months before sampling did not reduce their capacity to neutralize sanitizers. We developed a scheme to evaluate the ability of transport broths to neutralize QAC sanitizers. The three transport broths performed similarly with a commonly used concentration of quat, but Letheen broth could not effectively neutralize a very high concentration of QAC. The performance of transport broths was not significantly affected under the assessed pre-sampling and post-sampling storage conditions.

中文翻译：

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三种中和肉汤的比较，用于对不锈钢表面干燥并暴露于季铵化合物的低水平单核细胞增生李斯特菌进行环境采样

一种有效的环境采样方法涉及使用运输/中和肉汤，该肉汤能够中和采样过程中收集的消毒剂残留物，并保持受压力的单核细胞增生李斯特氏菌 (Lm) 细胞的活力。我们将 Lm 施加到不锈钢表面上，然后在室温（RT，21-24 °C）下对 Lm 施加干燥应力 16-18 小时。随后使用 Whisper™ V，一种基于季铵化合物 (QAC) 的消毒剂，稀释至 400 ppm 和 8000 ppm 的活性季铵盐，持续 6 小时。然后，我们用在三种运输肉汤 Dey/Engley (D/E) 肉汤、Letheen 肉汤和 HiCap™ 肉汤中预先润湿的海绵对 Lm 进行采样，以生成含有消毒剂残留物和低水平压力 Lm 的环境样品，随后对其进行分析通过基于富集的方法。该方案符合 AOAC International 的验证指南，每个肉汤使用 20 份含有低水平 Lm 的环境测试部分，因此并非所有测试部分都是阳性（即部分阳性）。我们表明，当没有季铵盐或 400 ppm 季铵盐应用于 Lm 污染不锈钢表面时，D/E 肉汤、Letheen 肉汤和 HiCap™ 肉汤表现相似。然而，当应用 8000 ppm 季铵盐时，Letheen 肉汤不能有效地中和样品中的 QAC。这些比较是在收集后在三种条件下储存的样品上进行的，以复制样品运输的场景，RT 2 小时，4°C 24 小时和 4°C 72 小时。三种不同情景下的比较大体上得出了相同的结论。此外，我们进一步证明，在采样前将 Letheen 和 HiCap™ 肉汤在室温下储存两个月不会降低它们中和消毒剂的能力。我们开发了一个方案来评估运输肉汤中和 QAC 消毒剂的能力。三种转运肉汤在常用的季铵盐浓度下表现相似，但 Letheen 肉汤不能有效地中和非常高浓度的 QAC。在评估的取样前和取样后储存条件下，运输肉汤的性能没有受到显着影响。但是 Letheen 肉汤不能有效地中和非常高浓度的 QAC。在评估的取样前和取样后储存条件下，运输肉汤的性能没有受到显着影响。但是 Letheen 肉汤不能有效地中和非常高浓度的 QAC。在评估的取样前和取样后储存条件下，运输肉汤的性能没有受到显着影响。