title: Dermatophyte identification using matrix-assisted laser desorption ionization-time of flight mass spectrometry.
abstract: The performance of the Bruker Biotyper matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometer (MS) for the identification of dermatophytes from clinical cultures was compared to that of dermatophyte identification using 28S rRNA gene sequencing. The MALDI Biotyper library (MBL; version 3.0) was used alone and in combination with a supplemented library containing an additional 20 dermatophyte spectra (S-MBL). Acquired spectra were interpreted using both the manufacturer-recommended scores (genus, ≥1.7; species, ≥2.0) and adjusted cutoff values established by this study (genus, ≥1.5; species, ≥1.7); identifications required a minimum 10% difference in scores between the top two different organisms to be considered correct. One hundred well-characterized, archived dermatophyte isolates and 71 fresh dermatophyte cultures were evaluated using both libraries and both sets of cutoff criteria. Collectively, the S-MBL significantly outperformed the MBL at both the genus (93% versus 37.4%; P < 0,0001) and species (59.6% versus 20.5%; P < 0.0001) levels when using the adjusted score criteria. Importantly, application of the lowered cutoff values significantly improved genus (P = 0.005)- and species (P < 0.0001)-level identification for the S-MBL, without leading to an increase in misidentifications. MALDI-TOF MS is a cost-effective and rapid alternative to traditional or molecular methods for dermatophyte identification, provided that the reference library is supplemented to sufficiently encompass clinically relevant, intraspecies strain diversity.
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Hilton 868, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Elitza S
authors.initials: ES
authors.lastname: Theel
authors.forename: Leslie
authors.initials: L
authors.lastname: Hall
authors.forename: Jayawant
authors.initials: J
authors.lastname: Mandrekar
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Wengenack
mesh_terms: D003883:Arthrodermataceae / Q000737:chemistry* / Q000145:classification* / Q000302:isolation & purification; D003881:Dermatomycoses / Q000175:diagnosis / Q000382:microbiology; D003951:Diagnostic Errors / Q000706:statistics & numerical data; D006801:Humans; D008828:Microbiological Techniques / Q000379:methods*; D025202:Molecular Diagnostic Techniques / Q000379:methods; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*