Inactivation by 405 ± 5 nm light emitting diode on Escherichia coli O157:H7, Salmonella Typhimurium, and Shigella sonnei under refrigerated condition might be due to the loss of membrane integrity

Kim, Minjeong; Mikš-Krajnik, Marta; Kumar, Amit; Yuk, Hyun‐Gyun

doi:10.1016/j.foodcont.2015.05.012

Cited by 67 publications

(45 citation statements)

References 41 publications

(62 reference statements)

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“…Our results show only a 6 to 10% higher level in cellular depolarization and permeability after LED illumination compared with levels in freshly cultured and nonilluminated control cells. Our previous studies also showed that only some of the illuminated S. Typhimurium cells lost membrane integrity under the same illumination conditions (11). Similar to our observations, Caminos et al (31) reported no change in the membrane integrity of E. coli after PDI with the aid of an exogenous photosensitizer, although membrane functions could have been lost.…”

Section: Discussionsupporting

confidence: 90%

“…Although the results of our previous studies demonstrated the antibacterial effect of a 405 Ϯ 5-nm LED on various foodborne pathogens and the damage to bacterial membranes (10,11), the detailed antibacterial mechanism of LED illumination on a given bacterial species had not been studied. Thus, this study was designed to assess the efficacy of LED illumination against Salmonella, to elucidate its antibacterial mechanism at membrane and gene levels, and to identify the factors influencing the differences in sensitivities to LED illumination.…”

Section: Discussionmentioning

confidence: 94%

“…Bacterial inactivation by LED illumination without any exogenous photosensitizer is theoretically due to the intracellular ROS generated by excited endogenous porphyrins naturally present in the cells (6,11). These ROS could nonspecifically damage cellular components, such as DNA, proteins, and lipids, eventually causing cell death.…”

Section: Discussionmentioning

confidence: 99%

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Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Kim

Yuk

2017

Appl Environ Microbiol

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The aim of this study was to elucidate the antibacterial mechanism of 405 Ϯ 5-nm light-emitting diode (LED) illumination against Salmonella at 4°C in phosphate-buffered saline (PBS) by determining endogenous coproporphyrin content, DNA oxidation, damage to membrane function, and morphological change. Gene expression levels, including of oxyR, recA, rpoS, sodA, and soxR, were also examined to understand the response of Salmonella to LED illumination. The results showed that Salmonella strains responded differently to LED illumination, revealing that S. enterica serovar Enteritidis (ATCC 13076) and S. enterica subsp. enterica serovar Saintpaul (ATCC 9712) were more susceptible and resistant, respectively, than the 16 other strains tested. There was no difference in the amounts of endogenous coproporphyrin in the two strains. Compared with that in nonilluminated cells, the DNA oxidation levels in illuminated cells increased. In illuminated cells, we observed a loss of efflux pump activity, damage to the glucose uptake system, and changes in membrane potential and integrity. Transmission electron microscopy revealed a disorganization of chromosomes and ribosomes due to LED illumination. The levels of the five genes measured in the nonilluminated and illuminated S. Saintpaul cells were upregulated in PBS at a set temperature of 4°C, indicating that increased gene expression levels might be due to a temperature shift and nutrient deficiency rather than to LED illumination. In contrast, only oxyR in S. Enteritidis cells was upregulated. Thus, different sensitivities of the two strains to LED illumination were attributed to differences in gene regulation.IMPORTANCE Bacterial inactivation using visible light has recently received attention as a safe and environmentally friendly technology, in contrast with UV light, which has detrimental effects on human health and the environment. This study was designed to understand how 405 Ϯ 5-nm light-emitting diode (LED) illumination kills Salmonella strains at refrigeration temperature. The data clearly demonstrated that the effectiveness of LED illumination on Salmonella strains depended highly on the serotype and strain. Our findings also revealed that its antibacterial mechanism was mainly attributed to DNA oxidation and a loss of membrane functions rather than membrane lipid peroxidation, which has been proposed by other researchers who studied the antibacterial effect of LED illumination by adding exogenous photosensitizers, such as chlorophyllin and hypericin. Therefore, this study suggests that the detailed antibacterial mechanisms of 405-nm LED illumination without additional photosensitizers may differ from that by exogenous photosensitizers. Furthermore, a change in stress-related gene regulation may alter the susceptibility of Salmonella cells to LED illumination at refrigeration temperature. Thus, our study provides new insights into the antibacterial mechanism of 405 Ϯ 5-nm LED illumination on Salmonella cells.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 94%

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Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Kim

Yuk

2017

Appl Environ Microbiol

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“…The maximum illumination time of 7.5 h was selected based on a previous study [4,13]. Bacterial suspension was also placed in the incubator without LED illumination (dark condition) as a non-illuminated control.…”

Section: Bacterial Inactivation By 405 ± 5 Nm Illuminationmentioning

confidence: 99%

“…Once bacteria are exposed to light energy in the presence of oxygen, the endogenous porphyrin compounds absorb the light and then are excited, resulting in production of reactive oxygen species (ROS) [9,12]. The ROS such as superoxide ions, hydroxyl radicals, hydrogen peroxide, and singlet oxygen may play the crucial role in a cytotoxic effect by reacting with intracellular components such as DNA, proteins, and lipids, resulting in bacterial death [4,13,14].…”

Section: Introductionmentioning

confidence: 99%