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J. Clin. Med. 2018, 7(9), 278; https://doi.org/10.3390/jcm7090278

Effects of 462 nm Light-Emitting Diode on the Inactivation of Escherichia coli and a Multidrug-Resistant by Tetracycline Photoreaction

1
Department of Science Education and Application, National Taichung University of Education, Taichung 40306, Taiwan
2
Department of Biotechnology, Ming-Chuan University, Gui-Shan 33343, Taiwan
3
Division of Infection, Department of Internal Medicine, National Cheng Kung University Hospital, Department of Medicine, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan
4
Tea Research and Extension Station, Taoyuan 32654, Taiwan
5
Department of Dermatology, National Cheng Kung University Hospital, Department of Biochemistry and Molecular Biology, College of Medicine, Center of Applied Nanomedicine, National Cheng Kung University, Tainan 70101, Taiwan
*
Authors to whom correspondence should be addressed.
Received: 13 August 2018 / Revised: 6 September 2018 / Accepted: 10 September 2018 / Published: 12 September 2018
(This article belongs to the Special Issue Advances in Antibacterial Drug Discovery and Therapy)
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Abstract

The adaptability of bacterial resistance to antibiotics contributes to its high efficiency during evolution. Tetracycline (TC) is a broad-spectrum antimicrobial agent. Chromatographic analyses and mass spectrometry were used to study the effects of the light illumination of a 462 nm light-emitting diode (LED) on the conformational changes of TC in a phosphate buffer solution (PBS, pH 7.8). Especially, the inactivation of superoxide anion radicals (O2) and Escherichia coli (E. coli), including that of a multidrug-resistant E. coli (MDR E. coli), were investigated during the photolysis of TC. A photolysis product of TC (PPT) was generated in an alkaline solution after the illumination of a blue light. The mass spectra of PPT had characteristic ion signals in m/z 459, 445, and 249.1 Da. The PPT has the molecular formula of C22H22N2O9, and the exact mass is 458.44 g/mol. The inactivation of MDR E. coli is not significant with TC treatment. The drug-resistant ability of MDR E. coli has a less significant effect on PPT, and the changed conformation of TC retained the inactivation ability of MDR E. coli upon blue light photoreaction. With TC, illuminated by a blue light in a pH 7.8 PBS, O2 was generated from TC photolysis, which enhanced the inactivation of E. coli and MDR E. coli. A 96.6% inactivation rate of MDR E. coli was reached with TC under 2.0 mW/cm2 blue light illumination at 25 ± 3 °C for 120 min, and the effects of the TC-treated photoreaction on MDR E. coli viability repressed the growth of MDR E. coli by 4 to 5 logs. The present study of the blue light photoreaction of TC offers a new approach to the inactivation of MDR E. coli. View Full-Text
Keywords: blue light; inactivation; MDR E. coli; skin and soft tissue infections (SSTIs); tetracycline blue light; inactivation; MDR E. coli; skin and soft tissue infections (SSTIs); tetracycline
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Huang, S.-T.; Wu, C.-Y.; Lee, N.; Cheng, C.-W.; Yang, M.-J.; Hung, Y.-A.; Wong, T.-W.; Liang, J.-Y. Effects of 462 nm Light-Emitting Diode on the Inactivation of Escherichia coli and a Multidrug-Resistant by Tetracycline Photoreaction. J. Clin. Med. 2018, 7, 278.

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