Abstract
Despite that matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has become a powerful tool in the clinical microbiology setting, few studies have till now focused on MALDI-TOF MS-based identification of dermatophytes. In this study, we analyze dermatophytes strains isolated from clinical samples by MALDI-TOF MS to supplement the reference database available in our laboratory. Twenty four dermatophytes (13 reference strains and 11 field isolated strains), identified by both conventional and molecular standard procedures, were analyzed by MALDI-TOF MS, and the spectra obtained were used to supplement the available database, limited to a few species. To verify the robustness of the implemented database, 64 clinical isolates other than those used for the implementation were identified by MALDI-TOF MS. The implementation allowed the identification of the species not included in the original database, reinforced the identification of the species already present and correctly identified those within the Trichophyton mentagrophytes complex previously classified as Trichophyton. tonsurans by MALDI-TOF MS. The dendrogram obtained by analyzing the proteic profiles of the different species of dermatophytes reflected their taxonomy, showing moreover, in some cases, a different clusterization between the spectra already present in the database and those newly added. In this study, MALDI-TOF MS proved to be a useful tool suitable for the identification of dermatophytes for diagnostic purpose.
Highlights
In the last few years, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been increasingly studied and was originally adapted for the identification of prokaryotic organisms
(three), Trichophyton rubrum, Trichophyton interdigitale, Trichophyton mentagrophytes and Trichophyton tonsurans, was supplemented with 13 proteic profiles of 13 different reference strains belonging to species of dermatophytes and proteic profiles belonging to eight species obtained from clinical isolates identified by both conventional methods and sequencing, for a total of 13 species (Table 1)
Each species used in this study to supplement the Bruker Daltonics database yielded a proteic profile, including unique peaks (Figure 1), so that each dermatophyte species analyzed gave a unique species-specific MALDI-TOF MS profile
Summary
In the last few years, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been increasingly studied and was originally adapted for the identification of prokaryotic organisms. New developments have extended its use to a few eukaryotic organisms, such as yeasts and molds, making this technique a straightforward, fast and reliable identification method for bacteria, yeasts and molds in a cost-effective way [1,2]. Dermatophytes, comprising species within the genera Epidermophyton, Microsporum and Trichophyton, are a unique group of closely-related filamentous fungi that invade keratinized cutaneous structures, including the stratum corneum, nails and hair of humans and animals, resulting in an infection referred to as dermatophytosis, ringworm or tinea [3,5]
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