Integrity of the Escherichia coli O157:H7 Cell Wall and Membranes After Chlorine Dioxide Treatment
Integrity of the Escherichia coli O157:H7 Cell Wall and Membranes After Chlorine Dioxide Treatment
复制标题
DOI：
10.3389/fmicb.2020.00888
复制
发表时间：
2020-05-15
影响因子：
5.2
通讯作者：
Wu, Vivian C. H.
中科院分区：
文献类型：
--
作者：
Bridges, David F.;Lacombe, Alison;Wu, Vivian C. H.
废水和新鲜农产品的处理通常使用氯作为抗菌剂。然而，人们越来越关注氯处理的安全性和抗菌功效。许多研究报告了二氧化氯（ClO 2）处理在各种应用中的抗菌性能，但有关ClO 2如何影响细菌的信息有限。在本研究中，使用定量和定性方法的混合方法来观察大肠杆菌O 157：暴露于ClO 2后H7膜损伤为进行比较，应用0.1%蛋白胨、70%异丙醇和10 mg/L NaOCl的对照物15 min。处理后，在覆盖有非选择性培养基的选择性培养基上对细胞计数，并同时使用以下荧光探针分析损伤：（1）Bis-（1，3-二丁基巴比妥酸）三甲氧酮（2）SYTO 9/碘化丙啶（LIVE/DEAD）用于膜渗透性，（3）2-（N-（7-硝基苯并-2-氧杂-1，3-二唑-4-基）氨基）-2-脱氧葡萄糖（2-NBDG），用于主动葡萄糖摄取，（4）丙二醛（MDA）积累引起的脂质过氧化作用。二氧化氯处理后的细菌对数减少范围为0.2至5.5，膜渗透性和葡萄糖摄取测定后相对荧光单位的变化与活力不一致，表明膜渗透性和代谢没有实质性改变。NaOCl处理后细胞出现去极化现象，而ClO 2处理后细胞的极性与水处理后细胞的极性相似（P < 0.05）。仅在10 mg/L ClO 2处理后才检测到MDA的积累，表明在较高浓度下发生了膜脂过氧化。透射电子显微镜成像显示，分离的细胞壁从胞质溶胶发生后，10 mg/L二氧化氯处理，但细胞壁本身似乎是完整的。表明ClO 2对E.大肠杆菌O 157：H7主要不位于细胞壁，并且在相当浓度下对细胞的伤害与NaOCl显著不同。
Treatments of wastewater and fresh produce commonly employ chlorine as an antimicrobial. However, there are increasing levels of concerns regarding the safety and antimicrobial efficacy of chlorine treatments. Numerous studies have reported the antimicrobial properties of chlorine dioxide (ClO2) treatment in a variety of applications but information regarding how ClO2 affects bacteria is limited. In the present study, a mixed-method approach utilizing both quantitative and qualitative methodologies was used to observe Escherichia coli O157:H7 membrane damage after exposure to ClO2 (2.5, 5, or 10 mg/L) for 5, 10, or 15 min. For comparison, controls of 0.1% peptone, 70% isopropanol, and 10 mg/L NaOCl were applied for 15 min. After treatment, cells were enumerated on selective media overlaid with non-selective media and simultaneously analyzed for damage using the following fluorescent probes (1) Bis-(1,3-Dibutylbarbituric Acid) trimethine oxonol (DiBAC4(3)) for membrane polarization, (2) SYTO 9/propidium iodide (LIVE/DEAD) for membrane permeability, (3) 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-Deoxyglucose (2-NBDG) for active glucose uptake, and (4) lipid peroxidation through accumulation of malondialdehyde (MDA). Bacterial log reductions after ClO2 treatment ranged from 0.2 to 5.5 and changes in relative fluorescence units after membrane permeability and glucose uptake assays were not consistent with viability, indicating membrane permeability and metabolism were not substantially altered. Depolarization was observed after NaOCl treatment, however, the polarity of cells treated with ClO2 were like those treated with water (P < 0.05). Accumulation of MDA was detected only after 10 mg/L ClO2 treatments, indicating that membrane peroxidation occurred at higher concentrations. Transmission electron microscopy imaging revealed that separation of the cell wall from the cytosol occurred after the 10 mg/L ClO2 treatment, but the cell wall itself appeared to be unbroken. These data suggest that ClO2 damage to E. coli O157:H7 is not primarily located at the cell wall and harms cells significantly different than NaOCl at comparable concentrations.