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The association of Yarrowia lipolytica with onychomycosis

Summary

A 20-year-old woman had a persistent toenail infection that did not respond to multiple antifungal treatments. Researchers identified the cause as Yarrowia lipolytica, an unusual yeast that had never been found causing nail infections before. The yeast was resistant to several common antifungal medications, explaining why previous treatments failed. This case shows the importance of identifying the exact fungus causing an infection to develop effective treatment strategies.

Background

Onychomycosis is a common fungal nail infection typically caused by dermatophytes or Candida species, affecting approximately 4% of people worldwide. Yarrowia lipolytica is a dimorphic yeast commonly found in hydrocarbon-rich environments and used in biotechnology, but has rarely been associated with human infections and never previously identified in onychomycosis cases.

Objective

To identify and characterize the causative fungal agent in a 20-year-old woman with persistent, treatment-resistant onychomycosis and tinea pedis unresponsive to standard antifungal therapies.

Results

Yarrowia lipolytica was repeatedly isolated from nail samples and confirmed through 98% nucleotide identity by ITS sequencing. The clinical isolate exhibited resistance to fluconazole, itraconazole, and posaconazole, but was susceptible to voriconazole. The resistance profile was consistent with the patient’s prior treatment failures.

Conclusion

This case represents the first documented association of Y. lipolytica with onychomycosis, highlighting the importance of thorough microbial identification and susceptibility testing in treatment-resistant nail infections. The antifungal resistance of this isolate complicated treatment options, particularly given the patient’s adverse reaction to prior azole therapies.
  • Published in:Medical Mycology Case Reports,
  • Study Type:Case Report,
  • Source: PMID: 40642207
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