Bridges David F, Lacombe Alison, Wu Vivian C H
Produce Safety and Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Albany, CA, United States.
Front Microbiol. 2022 Jun 17;13:923964. doi: 10.3389/fmicb.2022.923964. eCollection 2022.
Chlorine dioxide (ClO) and sodium hypochlorite (NaClO) are two chlorinated oxidizing agents that are implemented in water treatment and postharvest processing of fresh produce. While the antibacterial mechanisms of NaClO have been investigated, there are comparatively few studies that have looked at how ClO kills bacteria. Therefore, the objective of this study was to compare the inactivation pathways of ClO and NaClO against O157:H7. Treatments consisted of 2.5, 5, and 10 ppm ClO or 50, 100, and 200 ppm NaClO for 5, 10, and 15 min. Maximum log reductions of O157:H7 were 5.5 and 5.1 after treatment with ClO or NaClO, respectively. Bacterial inactivation was measured using log reductions, intracellular reactive oxygen species (ROS) using with 2',7'-dichlorofluorescin diacetate (DCFDA) or aminophenyl fluorescein (APF) probes, relative values of NAD, NADH, NADP, and NADPH cofactors. Additionally, the expression of three key genes involved in ROS stress was measured RT-PCR. Levels of intracellular ROS measured by DCFDA after ClO treatment were significantly higher than those found after treatment in NaClO. Additionally, NaClO treatment resulted in upregulation of ROS-defense genes, while expression of the same genes was typically at base levels or downregulated after ClO treatment. As the concentrations of both treatments increased, the NADP:NADPH ratio shifted to the cofactor being predominantly present as NADP. These data indicate that ClO and NaClO damage O157:H7 measurably different mechanisms and that ClO does not appear to cause substantial oxidative stress to O157:H7 directly.
二氧化氯（ClO）和次氯酸钠（NaClO）是两种用于新鲜农产品水处理和采后处理的氯化氧化剂。虽然已经对NaClO的抗菌机制进行了研究，但研究ClO如何杀死细菌的相对较少。因此，本研究的目的是比较ClO和NaClO对O157:H7的灭活途径。处理包括分别用2.5、5和10 ppm的ClO或50、100和200 ppm的NaClO处理5、10和15分钟。用ClO或NaClO处理后，O157:H7的最大对数减少量分别为5.5和5.1。使用对数减少量测量细菌灭活，使用2',7'-二氯荧光素二乙酸酯（DCFDA）或氨基苯基荧光素（APF）探针测量细胞内活性氧（ROS），以及测量NAD、NADH、NADP和NADPH辅因子的相对值。此外，通过RT-PCR测量参与ROS应激的三个关键基因的表达。ClO处理后用DCFDA测量的细胞内ROS水平显著高于NaClO处理后的水平。此外，NaClO处理导致ROS防御基因上调，而相同基因的表达在ClO处理后通常处于基础水平或下调。随着两种处理浓度的增加，NADP:NADPH比值向主要以NADP形式存在的辅因子转移。这些数据表明，ClO和NaClO通过明显不同的机制损伤O157:H7，并且ClO似乎不会直接对O157:H7造成实质性的氧化应激。
