Caspofungin alone or combined with polymyxin B are effective against mixed biofilm of Aspergillus fumigatus and carbapenem-resistant Pseudomonas aeruginosa

Aspergillus fumigatus and Pseudomonas aeruginosa biofilms are associated to the recalcitrant and persistent infections due to resistance to antimicrobials. Here, we evaluated the effect of antimicrobials on single and mixed biofilms of A. fumigatus and P. aeruginosa (carbapenem-resistant and susceptible strains) determining total biomass by crystal violet, cell viability by colony forming unit count, and microscopy. Polymyxin B (PMB) had the best action on P. aeruginosa biofilms inhibiting the biomass (2-4 mg/mL) and it was efficient reducing the viable bacterial cells. Amphotericin B (AMB) and caspofungin (CAS) were the best antifungal at inhibiting A. fumigatus biofilms and reducing fungal viability at con-centration >= 1 and >= 16 mg/mL, respectively. In addition, CAS was able to significantly reduce P. aeruginosa viability in mixed biofilms. CAS combined with PMB also significantly reduced the mixed biofilm biomass and fungal and bacterial viability mainly against carbapenem-resistant bacterium. The light and fluo-rescence microscopy showed alterations on hyphae morphology and confirmed the increase of fungal and bacterial death cells after combined therapy of mixed biofilms. Taken together, our work showed that CAS alone and its combination with PMB showed better potential in reducing mixed biofilm biomass and fungal and bacterial viability, even for the carbapenem-resistant P. aeruginosa strain. (c) 2022 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Automated summary

This study evaluated the effect of antimicrobials on single and mixed biofilms of Aspergillus fumigatus and Pseudomonas aeruginosa. The results showed that Polymyxin B had the best action on Pseudomonas aeruginosa biofilms, while Amphotericin B and caspofungin were the most effective antifungals for inhibiting Aspergillus fumigatus biofilms. Caspofungin also significantly reduced the viability of Pseudomonas aeruginosa in mixed biofilms. Microscopy confirmed changes in hyphae morphology and an increase in fungal and bacterial death cells after combined therapy of mixed biofilms.