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PLoS One. 2016 Nov 21;11(11):e0166325. doi: 10.1371/journal.pone.0166325. eCollection 2016.

Characteristics of Aspergillus fumigatus in Association with Stenotrophomonas maltophilia in an In Vitro Model of Mixed Biofilm.

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EA 7380 Dynamyc, Université Paris Est Créteil, Ecole nationale vétérinaire de d'Alfort, IMRB, Créteil, France.
Ecole nationale vétérinaire de Maisons-Alfort, Maisons-Alfort, France.
Cerba, Saint-Ouen l'Aumône, France.
Unité de Bactériologie-Hygiène, AP-HP, DHU VIC, Hôpital Henri Mondor, Département de Microbiologie, Créteil, France.
Unité des Aspergillus, Institut Pasteur, Paris, France.
Unité de Parasitologie-Mycologie, Département de Microbiologie, Hôpital Européen Georges Pompidou, Paris, France.
Unité de Mycologie, Département de Microbiologie, Groupe hospitalier Henri Mondor-Albert Chenevier, APHP, DHU VIC Université Paris-Est- Créteil, Créteil, France.



Biofilms are communal structures of microorganisms that have long been associated with a variety of persistent infections poorly responding to conventional antibiotic or antifungal therapy. Aspergillus fumigatus fungus and Stenotrophomonas maltophilia bacteria are examples of the microorganisms that can coexist to form a biofilm especially in the respiratory tract of immunocompromised patients or cystic fibrosis patients. The aim of the present study was to develop and assess an in vitro model of a mixed biofilm associating S. maltophilia and A. fumigatus by using analytical and quantitative approaches.


An A. fumigatus strain (ATCC 13073) expressing a Green Fluorescent Protein (GFP) and an S. maltophilia strain (ATCC 13637) were used. Fungal and bacterial inocula (105 conidia/mL and 106 cells/mL, respectively) were simultaneously deposited to initiate the development of an in vitro mixed biofilm on polystyrene supports at 37°C for 24 h. The structure of the biofilm was analysed via qualitative microscopic techniques like scanning electron and transmission electron microscopy, and fluorescence microscopy, and by quantitative techniques including qPCR and crystal violet staining.


Analytic methods revealed typical structures of biofilm with production of an extracellular matrix (ECM) enclosing fungal hyphae and bacteria. Quantitative methods showed a decrease of A. fumigatus growth and ECM production in the mixed biofilm with antibiosis effect of the bacteria on the fungi seen as abortive hyphae, limited hyphal growth, fewer conidia, and thicker fungal cell walls.


For the first time, a mixed A. fumigatus-S. maltophilia biofilm was validated by various analytical and quantitative approaches and the bacterial antibiosis effect on the fungus was demonstrated. The mixed biofilm model is an interesting experimentation field to evaluate efficiency of antimicrobial agents and to analyse the interactions between the biofilm and the airways epithelium.

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Conflict of interest statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: Over the past 5 years, FB has received grants from Astellas, payments for lectures from MSD, and travel expenses from Pfizer, MSD and Astellas. ED has received money for board membership from Astellas and Innothera, grants from Gilead, Ferrer, and Biorad, payments for lectures from Gilead and MSD, and travel expenses from MSD and Astellas. Other authors declare that they have no competing interest. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

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