School of Food Science and Engineering, South China University of Technology, Guangzhou, China.
Academy of Contemporary Food Engineering, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, China.
J Appl Microbiol. 2022 Oct;133(4):2348-2360. doi: 10.1111/jam.15688. Epub 2022 Aug 3.
The aim of the current study was to investigate the effect of plasma-mediated oxidative stress on the post-treatment viability of Listeria monocytogenes at the physiological and molecular levels.
10 CFU/ml L. monocytogenes in 10 ml phosphate-buffered saline (PBS) was treated with atmospheric non-thermal plasma for 0, 30, 60, 90 and 120 s respectively. Optical diagnostics using optical emission spectroscopy (OES) confirmed that dielectric barrier discharge (DBD) plasma was a significant source of ample exogenous reactive oxygen and nitrogen species (RONS). The development of extracellular main long-lived species was associated with plasma exposure time, accompanied by a massive accumulation of intracellular ROS in L. monocytogenes (p < 0.01). With the exception of virulence genes (hly), most oxidation resistance genes (e.g. sigB, perR, lmo2344, lmo2770 and trxA) and DNA repair gene (recA) were upregulated significantly (p < 0.05). A visible fragmentation in genomic DNA and a decline in the secretion of extracellular proteins and haemolytic activity (p < 0.01) were noticed. The quantitate oxygen consumption rates (OCRs) and extracellular acidification rates (ECARs) confirmed the viability attenuation from the aspect of energy metabolism. Survival assay in a real food system (raw milk) further suggested not only the viability attenuation, but also the resuscitation potential and safety risk of mild plasma-treated cells during post-treatment storage.
DBD plasma had the potential to inactivate and attenuate the virulence of L. monocytogenes, and it was recommended that plasma exposure time longer than 120 s was more suitable for attenuating viability and avoiding the recovery possibility of L. monocytogenes in raw milk within 7 days.
The current results presented a strategy to inactivate and attenuate the viability of L. monocytogenes, which could serve as a theoretical basis for better application of non-thermal plasma in food in an effort to effectively combat foodborne pathogens.
本研究旨在从生理和分子水平上探讨血浆介导的氧化应激对李斯特菌（Listeria monocytogenes）治疗后存活能力的影响。
将 10 毫升磷酸盐缓冲液（PBS）中 10CFU/ml 的单核细胞增生李斯特菌分别用大气压非热等离子体处理 0、30、60、90 和 120 秒。使用光谱发射光谱学（OES）的光学诊断证实，介质阻挡放电（DBD）等离子体是大量外源性活性氧和氮物质（RONS）的重要来源。细胞外主要长寿命物质的产生与等离子体暴露时间有关，同时单核细胞增生李斯特菌细胞内 ROS 大量积累（p<0.01）。除毒力基因（hly）外，大多数抗氧化基因（如 sigB、perR、lmo2344、lmo2770 和 trxA）和 DNA 修复基因（recA）均显著上调（p<0.05）。可见基因组 DNA 片段化，细胞外蛋白质分泌和溶血活性下降（p<0.01）。定量耗氧率（OCR）和细胞外酸化率（ECAR）从能量代谢方面证实了存活能力的衰减。在实际食品系统（生奶）中的存活实验进一步表明，不仅治疗后细胞的存活能力减弱，而且在治疗后 7 天内，轻度等离子体处理细胞的复苏潜力和安全性风险也增加。
DBD 等离子体具有灭活和削弱单核细胞增生李斯特菌毒力的潜力，建议等离子体暴露时间超过 120 秒更适合减弱其存活能力，并避免生奶中单核细胞增生李斯特菌在 7 天内恢复的可能性。
本研究提出了一种灭活和削弱单核细胞增生李斯特菌存活能力的策略，可为非热等离子体在食品中的更好应用提供理论依据，以有效对抗食源性致病菌。
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