AUTHOR=Kang Shenmin , Meng Yujie , Cheng Xiaomeng , Tu Junhong , Guo Du , Xu Yunfeng , Liang Sen , Xia Xiaodong , Shi Chao 

TITLE=Effects of 405-nm LED Treatment on the Resistance of Listeria monocytogenes to Subsequent Environmental Stresses

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01907

DOI=10.3389/fmicb.2019.01907

ISSN=1664-302X

ABSTRACT=<p><italic>Listeria monocytogenes</italic> can persist under a wide range of stress conditions, contributing to its ubiquitous distribution and unique pathogenic traits. Light from light-emitting diodes (LEDs) has recently been shown to inactivate various pathogens. Thus, the aim of the present study was to evaluate the effects of light treatment using a 405-nm LED on the subsequent resistance of <italic>L. monocytogenes</italic> to environmental stresses, including oxidative stress, ultraviolet (UV) irradiation, low temperature, osmotic pressure, simulated gastric fluid (SGF), and bile salts. Following 405-nm LED illumination at 4°C for 150 min, the survival of <italic>L. monocytogenes</italic> was examined after exposure to oxidative stress (0.04% H<sub>2</sub>O<sub>2</sub>), UV irradiation (253.7 nm), low temperature (4°C), osmotic pressure (10, 15, or 20% NaCl), SGF (pH 2.5), or bile salts (2%). The mechanisms responsible for changes in stress tolerance were identified by assessing the transcriptional responses and membrane integrity of <italic>L. monocytogenes</italic>. The 405-nm LED treatment reduced the resistance of <italic>L. monocytogenes</italic> to all the stresses tested. Reverse transcription quantitative real-time polymerase chain reaction analysis indicated that the transcription of multiple genes associated with stress resistance, including <italic>betL</italic>, <italic>gbuA</italic>, <italic>oppA</italic>, <italic>fri</italic>, <italic>bsh</italic>, and <italic>arcA</italic>, was reduced by 405-nm LED. Confocal laser scanning microscopy revealed that 405-nm LED treatment disrupted the integrity of the <italic>L. monocytogenes</italic> cell membrane compared with untreated bacteria. Therefore, 405-nm LED illumination appears to reduce the resistance of <italic>L. monocytogenes</italic> to various stress conditions. These findings suggest that 405-nm LED treatment could be used to effectively prevent and/or control with <italic>L. monocytogenes</italic> contamination along the entire food-processing chain, from production to consumption.</p>