Identification of clinical dermatophyte isolates obtained from Iran by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Background and Purpose: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used to discriminate among pathogenic microorganisms in clinical laboratories. The aim of this study was to assess the utility of MALDI-TOF MS in the routine identification of clinical dermatophyte isolates obtained from various geographical regions of Iran. Materials and Methods: A total of ۹۴ isolates, including Trichophyton interdigitale (n=۴۴), T. rubrum (n=۴۰), T. tonsurans (n=۴), Microsporum canis (n=۴), and Epidermophyton floccosum (n=۱), were analyzed in this study. The identity of each isolate was determined by polymerase chani reaction amplification and sequencing of the internal transcribed spacer (ITS) region of nuclear-encoded ribosomal DNA and also MALDI-TOF MS. The obtained data by molecular approach were compared with MALDI-TOF MS. Results: The MALDI-TOF MS led to the identification of ۴۴ (۴۷%) isolates at the species level by generating the spectral score values of ≥ ۲.۰. However, there was not sufficient agreement between the results of the molecular-based ITS identification methods and MALDI-TOF MS in the species identification of ۱۶ (۱۷%) isolates. The Bruker Daltonics database was also not able to identify protein spectra related to ۱۲ isolates (۱۳%), including T. interdigitale (n=۵), T. rubrum (n=۴), M. canis (n=۲), and T. tonsurans (n=۱). Conclusion: According to the results, the utility of MALDI-TOF MS as a routine diagnostic tool for the accurate and reliable identification of dermatophytes can be justified whenever the protein spectra of a large set of worldwide clinical isolates are included in the commercial libraries. In addition, MALDI-TOF MS can be alternatively used to construct an in-house reference database.

Keywords:

dermatophytes , Iran , ITS phylogeny , MALDI-TOF MS