Molecular ecology and pathogenic potential of Fonsecaea species

Area of Science:

• Medical Mycology
• Molecular Systematics
• Fungal Pathogenesis

Background:

• The genus Fonsecaea comprises fungi implicated in human chromoblastomycosis.
• Previous classifications relied on morphological characteristics, leading to ambiguity in species delineation.
• Understanding the genetic diversity and pathogenic potential of Fonsecaea is crucial for disease management.

Purpose of the Study:

• To revise the taxonomic classification of the genus Fonsecaea using molecular data.
• To differentiate between Fonsecaea species and their etiological roles in chromoblastomycosis.
• To investigate the genetic diversity within Fonsecaea strains.

Main Methods:

• Ribosomal DNA internal transcribed spacer (ITS) sequencing was employed for phylogenetic analysis.
• Randomly amplified polymorphic DNA (RAPD) typing was used for subspecific strain differentiation.
• Morphological characterization was performed to assess species distinctions.

Main Results:

• Two distinct species, Fonsecaea pedrosoi and the newly defined Fonsecaea monophora, were identified based on ITS sequence data.
• The classical distinction of Fonsecaea pedrosoi and Fonsecaea compacta was found to be invalid, with F. compacta being a morphological variant.
• Fonsecaea pedrosoi shows a strict association with human chromoblastomycosis, whereas F. monophora acts as a more general opportunist.
• Subspecific RAPD typing revealed significant strain diversity within Fonsecaea, alongside evidence of clonal reproduction.
• Fonsecaea-like environmental isolates were often more closely related to Cladophialophora species than to Fonsecaea.

Conclusions:

• The molecular revision clarifies the taxonomy of the genus Fonsecaea, establishing F. pedrosoi and F. monophora as the key species.
• Differential pathogenic roles in chromoblastomycosis are highlighted, with F. pedrosoi as a primary agent and F. monophora as an opportunist.
• High genetic diversity exists within Fonsecaea, necessitating further investigation into strain-level variations and their clinical relevance.
• Environmental isolates with Fonsecaea-like morphology may represent distinct taxa, potentially within the Cladophialophora genus, requiring careful identification in clinical settings.