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Title: Staphylococcus aureus resists UVA at low irradiance but succumbs in the presence of TiO2 photocatalytic coatings
Authors: Clemente, Andrea
Ramsden, J.J.
Wright, Alec
Iza, Felipe
Morrissey, Julie A.
Puma, Gianluca
Malik, Danish J.
Keywords: UVA
Reactive oxygen species
Staphylococcus aureus
Titanium dioxide
Issue Date: 2019
Publisher: © Elsevier
Citation: CLEMENTE, A. ... et al, 2019. Staphylococcus aureus resists UVA at low irradiance but succumbs in the presence of TiO2 photocatalytic coatings. Journal of Photochemistry and Photobiology B: Biology, 193, pp.131-139.
Abstract: The aim of this study was to evaluate the bactericidal effect of reactive oxygen species (ROS) generated upon irradiation of photocatalytic TiO2 surface coatings using low levels of UVA and the consequent killing of Staphylococcus aureus. The role of intracellular enzymes catalase and superoxide dismutase in protecting the bacteria was investigated using mutant strains. Differences were observed in the intracellular oxidative stress response and viability of S. aureus upon exposure to UVA; these were found to be dependent on the level of irradiance and not the total UVA dose. The wild type bacteria were able to survive almost indefinitely in the absence of the coatings at low UVA irradiance (LI, 1 mW/cm2), whereas in the presence of TiO2 coatings, no viable bacteria were measurable after 24 h of exposure. At LI, the lethality of the photocatalytic effect due to the TiO2 surface coatings was correlated with high intracellular oxidative stress levels. The wild type strain was found to be more resistant to UVA at HI compared with an identical dose at LI in the presence of the TiO2 coatings. The UVA-irradiated titania operates by a “stealth” mechanism at low UVA irradiance, generating low levels of extracellular lethal ROS against which the bacteria are defenceless because the low light level fails to induce the oxidative stress defence mechanism of the bacteria. These results are encouraging for the deployment of antibacterial titania surface coatings wherever it is desirable to reduce the environmental bacterial burden under typical indoor lighting conditions.
Description: This paper is closed access until 1 March 2020.
Sponsor: The authors would like to acknowledge EPSRC support for this work (Grant no. EP/M027341/1, Tackling Antimicrobial Resistance: An Interdisciplinary Approach), and support from the Collegium Basilea (Institute for Advanced Study), Basel, Switzerland.
Version: Accepted for publication
DOI: 10.1016/j.jphotobiol.2019.02.009
URI: https://dspace.lboro.ac.uk/2134/37187
Publisher Link: https://doi.org/10.1016/j.jphotobiol.2019.02.009
ISSN: 1011-1344
Appears in Collections:Closed Access (Chemical Engineering)

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