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The association of Yarrowia lipolytica with onychomycosis

Summary

A 20-year-old woman suffered from a persistent toenail infection that didn’t respond to several standard antifungal treatments over five years. Researchers identified the culprit as Yarrowia lipolytica, a rare yeast not previously known to cause nail infections. Testing showed this yeast was resistant to common antifungal medications the patient had received, explaining why previous treatments failed. This unusual case highlights the importance of properly identifying fungal pathogens and testing them for drug resistance before starting treatment.

Background

Onychomycosis is a common fungal nail infection typically caused by dermatophytes or Candida species. Yarrowia lipolytica is a dimorphic yeast rarely associated with human disease, more commonly found in hydrocarbon-rich environments and used in biotechnology applications. This case describes an unusual presentation of Y. lipolytica causing persistent nail infection unresponsive to standard antifungal treatments.

Objective

To identify the causative fungal pathogen in a 20-year-old woman with treatment-resistant onychomycosis and determine appropriate antifungal therapy. The study aimed to characterize the fungal isolate through microscopic examination, fungal culture, and molecular sequencing.

Results

Repeated isolation of Yarrowia lipolytica from nail samples was confirmed through ITS sequencing showing 98% nucleotide identity. The clinical isolate demonstrated dimorphic characteristics with budding yeasts and septate hyphae. Susceptibility testing revealed resistance to fluconazole, itraconazole, and posaconazole, with susceptibility only to voriconazole among azole antifungals tested.

Conclusion

This case represents the first reported association of Y. lipolytica with onychomycosis, highlighting the importance of thorough microbial identification and susceptibility testing in treatment-resistant nail infections. The antifungal resistance profile of the isolate explained prior treatment failures and underscores the need for species-specific identification in persistent fungal infections.
  • Published in:Medical Mycology Case Reports,
  • Study Type:Case Report,
  • Source: PMID: 40642207
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