Roussoella percutanea, a novel opportunistic pathogen causing subcutaneous mycoses.

Area of Science:

• Medical Mycology
• Fungal Taxonomy
• Molecular Phylogenetics

Background:

• Subcutaneous mycosis presents a diagnostic challenge, particularly in immigrant populations.
• Accurate identification of fungal pathogens is crucial for effective treatment strategies.

Observation:

• A novel fungal agent was isolated from a 45-year-old Indian male immigrant in the United States presenting with subcutaneous mycosis.
• Phylogenetic analysis using multiple genetic loci (SSU, LSU, ITS, TEF1, rPB2) confirmed the isolate's distinctiveness.

Findings:

• The novel fungus, named Roussoella percutanea, was phylogenetically placed within the order Pleosporales, family Arthopyreniaceae/Roussoellaceae.
• This new species is characterized by a delayed production of pycnidial conidiomata.
• Antifungal susceptibility testing revealed resistance to echinocandins and flucytosine, with variable responses to azoles and amphotericin B.

Implications:

• The identification of Roussoella percutanea expands the known spectrum of agents causing subcutaneous mycosis.
• Understanding the antifungal resistance profile is critical for guiding clinical management and developing targeted therapies.
• This discovery highlights the importance of molecular techniques in fungal diagnostics and taxonomy.