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Med Mycol. 2014 Nov;52(8):826-34. doi: 10.1093/mmy/myu064.

Identification of filamentous fungi isolates by MALDI-TOF mass spectrometry: clinical evaluation of an extended reference spectra library.

Author information

1
BCCM/IHEM fungal collection, Mycology and Aerobiology Laboratory, Scientific Institute of Public Health, Brussels, Belgium pierre.becker@wiv-isp.be.
2
Department of Microbiology and Infection Control, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
3
Department of Immunology and Microbiology, Université Libre de Bruxelles, Brussels, Belgium Department of Microbiology, Saint-Pierre University Hospital and Jules Bordet Institute, Brussels, Belgium.
4
APHM, CHU Timone-Adultes, Parasitology and Mycology, Marseille, France Aix Marseille Université, IP-TPT UMR MD3, Marseille, France.
5
BCCM/IHEM fungal collection, Mycology and Aerobiology Laboratory, Scientific Institute of Public Health, Brussels, Belgium.

Abstract

The identification of filamentous fungi by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) relies mainly on a robust and extensive database of reference spectra. To this end, a large in-house library containing 760 strains and representing 472 species was built and evaluated on 390 clinical isolates by comparing MALDI-TOF MS with the classical identification method based on morphological observations. The use of MALDI-TOF MS resulted in the correct identification of 95.4% of the isolates at species level, without considering LogScore values. Taking into account the Brukers' cutoff value for reliability (LogScore >1.70), 85.6% of the isolates were correctly identified. For a number of isolates, microscopic identification was limited to the genus, resulting in only 61.5% of the isolates correctly identified at species level while the correctness reached 94.6% at genus level. Using this extended in-house database, MALDI-TOF MS thus appears superior to morphology in order to obtain a robust and accurate identification of filamentous fungi. A continuous extension of the library is however necessary to further improve its reliability. Indeed, 15 isolates were still not represented while an additional three isolates were not recognized, probably because of a lack of intraspecific variability of the corresponding species in the database.

KEYWORDS:

MALDI-TOF MS; database; filamentous fungi; identification

PMID:
25349253
DOI:
10.1093/mmy/myu064
[Indexed for MEDLINE]

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