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Spectrum of clinically relevant Exophiala species in the United States

J S Zeng1, D A Sutton, A W Fothergill

  • 1Centraalbureau voor Schimmelcultures, NL-3508 AD, Utrecht, The Netherlands.

Journal of Clinical Microbiology
|June 29, 2007
PubMed

Insights

This study identifies 188 clinical Exophiala isolates using rRNA gene sequencing. Exophiala dermatitidis and E. xenobiotica were most common, causing deep and cutaneous infections, respectively.

Area of Science:

  • Medical Mycology
  • Clinical Microbiology
  • Molecular Diagnostics

Background:

  • Members of the genus Exophiala are recognized as significant agents of human and animal mycoses.
  • While most Exophiala infections are superficial or cutaneous, severe and fatal systemic infections are also documented.
  • Accurate identification of Exophiala species is crucial for understanding disease pathogenesis and guiding treatment.

Purpose of the Study:

  • To molecularly identify 188 clinical isolates of Exophiala species from the United States using internal transcribed spacer (ITS) sequencing.
  • To correlate specific Exophiala species with the types of infections they cause (cutaneous, superficial, subcutaneous, and systemic).
  • To assess the completeness of the known opportunistic Exophiala species list in temperate climates.

Main Methods:

  • Morphological identification of 188 clinical isolates.
  • DNA extraction and sequencing of the internal transcribed spacer (ITS) region of the rRNA gene.
  • Phylogenetic analysis and comparison with reference sequences for species identification.

Main Results:

  • Molecular identification revealed the most frequent species as Exophiala dermatitidis (29.3%), E. xenobiotica (19.7%), and E. oligosperma (18.6%).
  • Exophiala strains were frequently isolated from deep systemic infections (39.9%) and cutaneous infections (38.3%).
  • E. dermatitidis, E. oligosperma, E. phaeomuriformis, E. xenobiotica, and E. lecanii-corni were predominantly associated with systemic infections, while other species caused cutaneous and subcutaneous infections.

Conclusions:

  • The study provides a comprehensive molecular identification of clinical Exophiala isolates, highlighting the prevalence of specific species in causing diverse mycoses.
  • The findings suggest that the current understanding of opportunistic Exophiala species in temperate regions is nearing completion, although further species descriptions may be warranted.
  • Accurate molecular identification is essential for differentiating pathogenic Exophiala species and understanding their clinical significance.

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