%0 Figure %A Kang, Shenmin %A Meng, Yujie %A Cheng, Xiaomeng %A Tu, Junhong %A Guo, Du %A Xu, Yunfeng %A Liang, Sen %A Xia, Xiaodong %A Shi, Chao %D 2019 %T Image_1_Effects of 405-nm LED Treatment on the Resistance of Listeria monocytogenes to Subsequent Environmental Stresses.TIF %U https://frontiersin.figshare.com/articles/figure/Image_1_Effects_of_405-nm_LED_Treatment_on_the_Resistance_of_Listeria_monocytogenes_to_Subsequent_Environmental_Stresses_TIF/9638288 %R 10.3389/fmicb.2019.01907.s001 %2 https://frontiersin.figshare.com/ndownloader/files/17291288 %K L. monocytogenes %K LED %K environmental stress resistance %K cell membrane integrity %K resistance gene %X

Listeria monocytogenes 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 L. monocytogenes 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 L. monocytogenes was examined after exposure to oxidative stress (0.04% H2O2), 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 L. monocytogenes. The 405-nm LED treatment reduced the resistance of L. monocytogenes 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 betL, gbuA, oppA, fri, bsh, and arcA, was reduced by 405-nm LED. Confocal laser scanning microscopy revealed that 405-nm LED treatment disrupted the integrity of the L. monocytogenes cell membrane compared with untreated bacteria. Therefore, 405-nm LED illumination appears to reduce the resistance of L. monocytogenes to various stress conditions. These findings suggest that 405-nm LED treatment could be used to effectively prevent and/or control with L. monocytogenes contamination along the entire food-processing chain, from production to consumption.

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