Evaluation of the MALDI-TOF mass spectrometry technique for the identification of dermatophytes: Use of an extended database

Background

Identification of dermatophytes is usually performed through morphological analyses. However, it may be hindered due to the discovery of new species and complexes and, with some isolates, by the absence of fructification. Matrix-assisted laser desorption/ionisation-time-of-flight mass spectrometry (MALDI-TOF MS) seems to be an option for improving identification.

Aims

To develop a database (DB) for the identification of dermatophytes with MALDI-TOF MS, including 32 isolates from the Red de Micología de la Ciudad Autónoma de Buenos Aires [Mycology Network of the Autonomous City of Buenos Aires] (RMCABA) and one reference isolate (RMCABA DB), and evaluate its performance when added to the DB from the supplier, Bruker (Bruker DB).

Methods

All the isolates in the RMCABA DB were identified based on morphology and sequencing. To evaluate the performance of the extended DB (Bruker DB plus RMCABA DB), 136 clinical isolates were included.

Results

The percentages of identification at the species level increased from 45% to 88%, but the identification at the genus level decreased from 23% to 7%.

Conclusions

MALDI-TOF MS yielded better performance in the identification of dermatophytes after including the RMCABA DB, which encompassed local isolates.