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Pseudomonas aeruginosa increases the susceptibility of Candida albicans to amphotericin B in dual species biofilms

Alam, Farhana, Blackburn, Sarah Amy, Davis, Jack, Correia, Joao N., Tsai, Hung-Ji, Blair, Jessica M A, Hall, Rebecca A. (2023) Pseudomonas aeruginosa increases the susceptibility of Candida albicans to amphotericin B in dual species biofilms. Journal of Antimicrobial Chemotherapy, 78 (9). pp. 2228-2241. ISSN 0305-7453. (doi:10.1093/jac/dkad228) (KAR id:102028)

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Biofilms are the leading cause of nosocomial infections and are hard to eradicate due to their inherent antimicrobial resistance. Candida albicans is the leading cause of nosocomial fungal infections and is frequently co-isolated with the bacterium Pseudomonas aeruginosa from biofilms in the Cystic Fibrosis lung and severe burn wounds. The presence of C. albicans in multi-species biofilms is associated with enhanced antibacterial resistance, which is largely mediated through fungal extracellular carbohydrates sequestering the antibiotics. However, significantly less is known regarding the impact of polymicrobial biofilms on antifungal resistance.


Here we show that, in dual species biofilms, P. aeruginosa enhances the susceptibility of C. albicans to amphotericin B, an effect that was biofilm specific. Transcriptional analysis combined with gene ontology enrichment analysis identified several C. albicans processes associated with oxidative stress to be differentially regulated in dual species biofilms, suggesting that P. aeruginosa exerts oxidative stress on C. albicans, likely through the secretion of phenazines. However, the mitochondrial superoxide dismutase SOD2 was significantly downregulated in the presence of P. aeruginosa. Mono-species biofilms of the sod2 mutant were more susceptible to amphotericin B, and the susceptibility of these biofilms was further enhanced by exogenous phenazines.


We propose that in dual species biofilms, P. aeruginosa simultaneously induces mitochondrial oxidative stress, whilst downregulating key detoxification enzymes, which prevent C. albicans mounting an appropriate oxidative stress response to amphotericin B, leading to fungal cell death. This work highlights the importance of understanding the impact of polymicrobial interactions on antimicrobial susceptibility.

Item Type: Article
DOI/Identification number: 10.1093/jac/dkad228
Additional information: For the purpose of open access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.
Uncontrolled keywords: Infectious Diseases, Pharmacology (medical), Pharmacology, Microbiology (medical)
Subjects: Q Science > QR Microbiology
Divisions: Divisions > Division of Natural Sciences > Biosciences
Funders: Biotechnology and Biological Sciences Research Council (
Medical Research Council (
Wellcome Trust (
Depositing User: Becky Hall
Date Deposited: 10 Jul 2023 15:30 UTC
Last Modified: 10 Jan 2024 12:21 UTC
Resource URI: (The current URI for this page, for reference purposes)

University of Kent Author Information

Blackburn, Sarah Amy.

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Davis, Jack.

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Hall, Rebecca A..

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