Use of the Bruker MALDI Biotyper for identification of molds in the clinical mycology laboratory.
Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is increasingly used for the identification of bacteria and fungi in the diagnostic laboratory. We evaluated the mold database of Bruker Daltonik (Bremen, Germany), the Filamentous Fungi Library 1.0. First, we studied 83 phenotypically and molecularly well-characterized, nondermatophyte, nondematiaceous molds from a clinical strain collection. Using the manufacturer-recommended interpretation criteria, genus and species identification rates were 78.3% and 54.2%, respectively. Reducing the species cutoff from 2.0 to 1.7 significantly increased species identification to 71.1% without increasing misidentifications. In a subsequent prospective study, 200 consecutive clinical mold isolates were identified by the MALDI Biotyper and our conventional identification algorithm. Discrepancies were resolved by ribosomal DNA (rDNA) internal transcribed spacer region sequence analysis. For the MALDI Biotyper, genus and species identification rates were 83.5% and 79.0%, respectively, when using a species cutoff of 1.7. Not identified were 16.5% of the isolates. Concordant genus and species assignments of MALDI-TOF MS and the conventional identification algorithm were observed for 98.2% and 64.2% of the isolates, respectively. Four erroneous species assignments were observed using the MALDI Biotyper. The MALDI Biotyper seems highly reliable for the identification of molds when using the Filamentous Fungi Library 1.0 and a species cutoff of 1.7. However, expansion of the database is required to reduce the number of nonidentified isolates.
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland schulthe@imm.uzh.ch.
Bettina
B
Schulthess
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
Raphael
R
Ledermann
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
Forouhar
F
Mouttet
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
Andrea
A
Zbinden
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
Guido V
GV
Bloemberg
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
Erik C
EC
Böttger
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
Michael
M
Hombach
D019411:Clinical Laboratory Techniques / Q000379:methods*; D005658:Fungi / Q000145:classification* / Q000302:isolation & purification*; D006801:Humans; D009181:Mycoses / Q000175:diagnosis* / Q000382:microbiology*; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation* / Q000379:methods*