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Open AccessArticle

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

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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