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Biofilm Formation by Pseudallescheria/Scedosporium Species: A Comparative Study
Rodrigo Rollin-Pinheiro1, Jardel V de Meirelles1, Taissa V M Vila2
1Laboratório de Química Biológica de Microrganismos, Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de JaneiroRio de Janeiro, Brazil.
Abstract:
Pseudallescheria/Scedosporium species are medically important fungi that are present in soil and human impacted areas and capable of causing a wide spectrum of diseases in humans. Although little is known about their pathogenesis, their growth process and infection routes are very similar to those of Aspergillus species, which grow as biofilms in invasive infections. All nine strains tested here displayed the ability to grow as biofilms in vitro and to produce a dense network of interconnected hyphae on both polystyrene and the surfaces of central venous catheters, but with different characteristics. Scedosporium boydii and S. aurantiacum clinical isolates were able to form biofilms faster than the corresponding environmental strains, as evidenced in kinetic assays for S. boydii and CLSM for S. aurantiacum. Biofilms formed by Pseudallescheria/Scedosporium species had significantly higher resistance to the class of antifungal azole than was observed in planktonic cells, indicating a protective role for this structure. In addition, the clinical S. aurantiacum isolate that formed the most robust biofilms was also more virulent in a larvae Galleria mellonella infection model, suggesting that the ability to form biofilms enhances virulence in Pseudallescheria/Scedosporium species.
Insights
Pseudallescheria/Scedosporium fungi form biofilms, enhancing their resistance to antifungals and increasing virulence. Clinical strains form biofilms faster than environmental ones, impacting disease severity.
Area of Science:
- Medical Mycology
- Fungal Pathogenesis
- Antimicrobial Resistance
Background:
- Pseudallescheria/Scedosporium are medically significant fungi found in soil and contaminated environments.
- These fungi cause various human diseases, with pathogenesis similar to Aspergillus species.
- Fungal biofilms are crucial in invasive infections, offering protection and contributing to virulence.
Purpose of the Study:
- To investigate the in vitro biofilm formation capabilities of Pseudallescheria/Scedosporium species.
- To compare biofilm formation between clinical and environmental isolates.
- To assess the impact of biofilm formation on antifungal resistance and virulence.
Main Methods:
- In vitro biofilm assays on polystyrene and central venous catheter surfaces.
- Kinetic assays and confocal laser scanning microscopy (CLSM) for biofilm characterization.
- Antifungal susceptibility testing of planktonic and biofilm cells.
- Galleria mellonella larvae infection model to evaluate virulence.
Main Results:
- All nine tested strains formed biofilms with varying characteristics on different surfaces.
- Clinical isolates of Scedosporium boydii and S. aurantiacum formed biofilms more rapidly than environmental strains.
- Pseudallescheria/Scedosporium biofilms exhibited significantly increased resistance to azole antifungals compared to planktonic cells.
- A highly virulent clinical S. aurantiacum isolate formed robust biofilms, correlating biofilm formation with enhanced virulence in vivo.
Conclusions:
- Pseudallescheria/Scedosporium species possess a significant capacity for in vitro biofilm formation.
- Biofilm formation confers substantial resistance to azole antifungals, highlighting a key survival mechanism.
- Enhanced biofilm formation in clinical isolates correlates with increased virulence, suggesting a role in disease progression.
