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The role of melanin in Aspergillus tolerance to biocides and photosensitizers

Pascoe, M. J. and Maillard, J. -Y. 2021. The role of melanin in Aspergillus tolerance to biocides and photosensitizers. Letters in Applied Microbiology 72 (4) , pp. 375-381. 10.1111/lam.13437

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Abstract

Cationic biocides are widely utilized for surface disinfection. Photosensitizers such as toluidine blue O (TBO) produce reactive oxygen species following light excitation and are being investigated as novel biocides for similar applications. Aspergillus brasiliensis conidia contain melanin which protects against environmental stressors. The negative charge and antioxidant properties of melanin may confer resistance to photosensitizers and other biocides. In this study, the yeasticidal and fungicidal activity benzalkonium chloride (BZC), sodium dichloroisocyanurate (NaDCC) and TBO with red light were examined using quantitative suspension tests. All three biocides were highly effective against Candida albicans and > 5·0 log10 reductions in viability were attainable within 5 minutes. Wild‐type A. brasiliensis conidia were highly tolerant to treatment and 0·4 log10 reductions in viability were observed within the same time frame when treated with TBO or BZC. NaDCC was markedly more effective. Inhibition of melanin biosynthesis by culturing with 100 μg ml−1 kojic acid resulted in a hypopigmented phenotype with significantly increased sensitivity to all three biocides. These observations indicate that melanin is a significant contributor towards A. brasiliensis tolerance of biocides and photosensitizers and demonstrate that cationic biocides are poorly suited to applications where the control of A. brasiliensis is required.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Pharmacy
Additional Information: This is an open access article under the terms of the Creative Commons Attribution License
Publisher: Wiley
ISSN: 0266-8254
Date of First Compliant Deposit: 4 January 2021
Date of Acceptance: 26 November 2020
Last Modified: 28 Apr 2021 12:21
URI: http://orca.cf.ac.uk/id/eprint/137289

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