The use of electrolyzed oxidizing (EO) water to inactivate microorganisms on foods has been extensively studied and shown to be effective. However, the prospect of the formation of "viable but nonculturable" (VBNC) cells in pathogens after low free chlorine concentration (FCC) treatments under high organic loads presents safety concerns. This study investigated the effect of EO water FCC on inducing Escherichia coli O157:H7 and Listeria monocytogenes into the VBNC state and studied possible resuscitation triggering procedures of the VBNC cells. A 5-strain cocktail of each pathogen (106 colony forming units [CFU]/mL) was exposed to EO water (FCC of 20, 10, 5, 2.5, 1.25, 0.625 mg/L) and allowed to stand for 1 and 5 min, followed by the addition of neutralizing broth. Treated samples were plated on nonselective agar and analyzed using flow cytometry. For resuscitation, samples treated with identified VBNC induction conditions were exposed to elevated temperatures (37 °C) as well as addition of sodium pyruvate (SP) and Tween® 20 (T20) solutions. The initial culturing procedures suggested complete inactivation of both pathogens at 2.5 and 1.25 mg/L FCC in the growth medium. However, flow cytometry profiles showed VBNC cells were present. Subjecting samples to the recovery procedures further proved that VBNC E. coli O157:H7 can be resuscitated after exposure to SP and T20 at 37 °C, while L. monocytogenes did not resuscitate. These findings show that treating pathogens at low FCC can induce the VBNC state, and culturability of E. coli O157:H7 can be restored under appropriate conditions. PRACTICAL APPLICATION VBNC induction conditions for foodborne pathogens during chlorine washing treatment were determined in a broth system and the information can serve as a basis for future studies that address the prevention of VBNC formation during produce wash treatments.

中文翻译：

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使用流式细胞术和标准电镀检测和验证大肠杆菌 O157:H7 和单核细胞增生李斯特菌的活但不可培养 (VBNC) 状态

使用电解氧化 (EO) 水灭活食品上的微生物已被广泛研究并证明是有效的。然而，在高有机负荷下低游离氯浓度 (FCC) 处理后，病原体中“有活力但不可培养” (VBNC) 细胞的形成前景存在安全问题。本研究调查了 EO 水 FCC 对诱导大肠杆菌 O157:H7 和单核细胞增生李斯特菌进入 VBNC 状态的影响，并研究了 VBNC 细胞可能的复苏触发程序。将每种病原体的 5 株混合物（106 个菌落形成单位 [CFU]/mL）暴露于 EO 水（FCC 为 20、10、5、2.5、1.25、0.625 mg/L）并静置 1 和 5分钟，然后加入中和肉汤。将处理过的样品置于非选择性琼脂上并使用流式细胞仪进行分析。对于复苏，用确定的 VBNC 诱导条件处理的样品暴露于高温 (37 °C) 以及添加丙酮酸钠 (SP) 和 Tween® 20 (T20) 溶液。最初的培养程序表明在生长培养基中 2.5 和 1.25 mg/L FCC 两种病原体完全灭活。然而，流式细胞仪分析显示存在 VBNC 细胞。对样本进行恢复程序进一步证明，VBNC 大肠杆菌 O157:H7 在 37°C 暴露于 SP 和 T20 后可以复苏，而单核细胞增生李斯特菌没有复苏。这些发现表明，在低 FCC 下处理病原体可以诱导 VBNC 状态，并且可以在适当的条件下恢复大肠杆菌 O157:H7 的可培养性。