Identification of Challenging Dermatophyte Species Using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a widely adopted technique for bacterial and yeast identification in clinical laboratories but is less frequently applied to filamentous fungi due to inconsistent performance, limitations of commercial libraries, and variability of preparation methods. This study aimed to validate the efficiency of MALDI-TOF MS-based dermatophyte identification using the Bruker Biotyper system. Focusing on species from the Trichophyton, Nannizzia, Microsporum, and Epidermophyton genera, an in-house reference library was established and evaluated with clinical isolates. The expanded library, which combined the in-house and Bruker libraries, achieved significantly higher accuracy than the Bruker library alone, correctly identifying 90.7% (107/118) of isolates at the species level compared to 16.1% (19/118) by the Bruker library. This study presents an efficient, standardized MALDI-TOF MS protocol for routine dermatophyte identification and provides a review of the current status and influencing factors in MALDI-TOF MS-based dermatophyte identification strategies.