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Staphylococcus aureus small colony variants are susceptible to light activated antimicrobial agents

Tubby, S; Wilson, M; Wright, JA; Zhang, P; Nair, SP; (2013) Staphylococcus aureus small colony variants are susceptible to light activated antimicrobial agents. BMC Microbiology , 13 , Article 201. 10.1186/1471-2180-13-201. Green open access

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Abstract

Background: Antibiotic therapy can select for small colony variants of Staphylococcus aureus that are more resistant to antibiotics and can result in persistent infections, necessitating the development of more effective antimicrobial strategies to combat small colony variant infections. Photodynamic therapy is an alternative treatment approach which utilises light in combination with a light-activated antimicrobial agent to kill bacteria via a non-specific mechanism of action. In this study, we investigated whether the combination of 665 nm laser light and the light-activated antimicrobial agent methylene blue was able to successfully kill S. aureus small colony variants. S. aureus and isogenic stable small colony variant were exposed to varying doses (1.93 to 9.65 J/cm2) of 665 nm laser light in the presence of varying concentrations (1 to 20 μM) of methylene blue. Results: The combination of 665 nm laser light and methylene blue was found to be an effective strategy for the killing of small colony variants. At the highest light dose (9.65 J/cm2) and methylene blue concentration (20 μM) tested, the number of viable bacteria decreased by approximately 6.9 log10 for the wild type and approximately 5 log10 for the small colony variant. Conclusions: These results suggest that photodynamic therapy has potential for use in the treatment of superficial infections caused by small colony variants of S. aureus and supports further research in this field.

Type: Article
Title: Staphylococcus aureus small colony variants are susceptible to light activated antimicrobial agents
Open access status: An open access version is available from UCL Discovery
DOI: 10.1186/1471-2180-13-201
Publisher version: http://dx.doi.org/10.1186/1471-2180-13-201
Language: English
Additional information: © 2013 Tubby et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Keywords: Staphylococcus aureus, Lethal photosensitisation, Photodynamic therapy, Small colony variant
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Eastman Dental Institute
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Eastman Dental Institute > Microbial Diseases
URI: https://discovery.ucl.ac.uk/id/eprint/1412140
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