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Journal of Clinical Microbiology, September 2009, p. 2912-2917, Vol. 47, No. 9
0095-1137/09/$08.00+0 doi:10.1128/JCM.00389-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for Fast and Reliable Identification of Clinical Yeast Isolates
G. Marklein,1
M. Josten,1
U. Klanke,1
E. Müller,1
R. Horré,3
T. Maier,2
T. Wenzel,2
M. Kostrzewa,2
G. Bierbaum,1
A. Hoerauf,1 and
H.-G. Sahl1*
Institute of Medical Microbiology, Immunology and Parasitology, Rheinische Friedrich-Wilhelms-Universität, University of Bonn, Bonn, Germany,1 Bruker Daltonik GmbH, Bremen, Germany,2 Federal Institute for Drugs and Medical Devices (BfArM), Bonn, Germany3
Received 20 February 2009/ Returned for modification 9 April 2009/ Accepted 22 June 2009
The clinical impact of severe infections with yeasts and yeast-like fungi has increased, especially in immunocompromised hosts. In recent years, new antifungal agents with different and partially species-specific activity patterns have become available. Therefore, rapid and reliable species identification is essential for antifungal treatment; however, conventional biochemical methods are time-consuming and require considerable expertise. We evaluated matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for the rapid routine identification of clinical yeast isolates. A total of 18 type collection strains and 267 recent clinical isolates of Candida (n = 250), Cryptococcus, Saccharomyces, Trichosporon, Geotrichum, Pichia, and Blastoschizomyces spp. were identified by MALDI-TOF MS. The results were compared with those obtained by conventional phenotyping and biochemical tests, including the API ID 32C system (bioMérieux, Nürtingen, Germany). Starting with cells from single colonies, accurate species identification by MALDI-TOF MS was achieved for 247 of the clinical isolates (92.5%). The remaining 20 isolates required complementation of the reference database with spectra for the appropriate reference strains which were obtained from type culture collections or identified by 26S rRNA gene sequencing. The absence of a suitable reference strain from the MALDI-TOF MS database was clearly indicated by log(score) values too low for the respective clinical isolates; i.e., no false-positive identifications occurred. After complementation of the database, all isolates were unambiguously identified. The established API ID 32C biochemical diagnostic system identified 244 isolates in the first round. Overall, MALDI-TOF MS proved a most rapid and reliable tool for the identification of yeasts and yeast-like fungi, with the method providing a combination of the lowest expenditure of consumables, easy interpretation of results, and a fast turnaround time.
* Corresponding author. Mailing address: Institute of Medical Microbiology, Immunology and Parasitology, Sigmund Freud Straße 25, Bonn D-53127, Germany. Phone: 49(0)228 287-16483. Fax: 49(0)228 287-14808. E-mail: sahl{at}microbiology-bonn.de
Published ahead of print on 1 July 2009.
Journal of Clinical Microbiology, September 2009, p. 2912-2917, Vol. 47, No. 9
0095-1137/09/$08.00+0 doi:10.1128/JCM.00389-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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