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In high iron environment, pyocyanin is a major anti-Aspergillus molecule

Chatterjee, Paulami, Sass, Gabriele, Nazik, Hasan, Déziel, Éric et Stevens, David A . In high iron environment, pyocyanin is a major anti-Aspergillus molecule In: 9th Advances Against Aspergillosis and Mucormycosis conference, 27-29 February 2020, Lugano, Suisse.

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Résumé

Purpose:

Airways of immunocompromised patients, or individuals with cystic fibrosis, are common ground for Pseudomonas aeruginosa and Aspergillus fumigatus infections. Hence, in such a microenvironment both pathogens compete for resources. In recent studies we showed that the siderophore pyoverdine is the most anti-fungal P. aeruginosa product under low iron conditions. We now investigated activity of P. aeruginosa against A. fumigatus biofilms under high iron conditions.

Methods:

P. aeruginosa wildtype strains PA14 and PAO1, as well as PA14 mutants pvdD-, pchE-, pvdD-pchE-, pqsA-, pqsH-, rhlR-, lasR-, lasR-rhlR-, and lasI- were cultivated in RPMI 1640 minimal medium with or without addition of ferric iron (iron), or blood at 37oC and 100 rpm for 24 hours. Bacterial supernatants were tested for bacterial growth (A600 nm), and filter sterilized (0.22 μm). Pyoverdine (A405 nm, and UV test), pyocyanin (A360 nm, or A540 nm following chloroform extraction) in supernatants were measured. Supernatants, or purified molecules alone, were assayed for effects on A.fumigatus biofilm formation, as well as A. fumigatus preformed biofilms.

Results:

Under high iron conditions P.aeruginosa supernatants no longer contained pyoverdine, but still possessed considerable anti-fungal activity. Spectrometric analysis of P.aeruginosa PA14 wildtype supernatant revealed the presence of the toxin pyocyanin. In response to iron, pyocyanin was not found in supernatants of PA14 mutants defective in phenazine production. Supernatants without pyocyanin under high iron conditions were significantly less anti-fungal towards A.fumigatusbiofilms. Pure pyocyanin, at concentrations measured in PA14 supernatants, interfered with A.fumigatus biofilm metabolism. When blood (as a natural source of iron), as low as 0.5%, was added during P aeruginosa supernatant production, pyoverdine disappeared from supernatants, and pyocyanin appeared. Although pyoverdine was no longer present in those supernatants, strong anti-fungal activity against A. fumigatus biofilms was observed. Neither iron, nor blood, induced pyocyanin production by PAO1, indicating important differences between standard reference P.aeruginosa strains. Under high iron conditions PAO1 supernatants showed significantly lower anti-fungal activity than PA14 supernatants.

Conclusion:

While under low iron conditions the major anti-fungal product of P. aeruginosa is pyoverdine, under high iron conditions, pyoverdine is no longer present, giving rise to the expectation of lower anti-fungal activity of P.aeruginosa supernatants. In fact, anti-fungal activity of supernatants under high iron conditions was only lower when strains were not able to deliver the P.aeruginosa toxin pyocyanin in response to iron. Under high iron conditions pyocyanin therefore appears to replace the anti-fungal activity of pyoverdine observed under low iron conditions. In conclusion, P.aeruginosa has mechanisms to compete with Aspergillus fumigatus under low or high iron conditions, and can switch from iron-denial-based (pyoverdine-based) to toxin-based (pyocyanin-based) anti-fungal activity.

Type de document: Document issu d'une conférence ou d'un atelier
Informations complémentaires: Affiche scientifique no 75 en page 150 du document des actes de la conférence qui se trouvent à l'adresse URL suivante: https://aaam2020.org/wp-content/uploads/2020/02/AAAM2020_AbstractBook.pdf page 150
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Centre: Centre INRS-Institut Armand Frappier
Date de dépôt: 14 juill. 2021 15:51
Dernière modification: 14 juill. 2021 15:51
URI: https://espace.inrs.ca/id/eprint/11821

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