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Front Microbiol. 2015 Jul 8;6:679. doi: 10.3389/fmicb.2015.00679. eCollection 2015.

Evaluation of the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry Bruker Biotyper for identification of Penicillium marneffei, Paecilomyces species, Fusarium solani, Rhizopus species, and Pseudallescheria boydii.

Author information

1
Division of Infectious Diseases, Department of Internal Medicine, Cardinal Tien Hospital New Taipei City, Taiwan.
2
Division of Infectious Diseases, Department of Internal Medicine, Cardinal Tien Hospital New Taipei City, Taiwan ; Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University Taipei, Taiwan.
3
Department of Graduate Institute of Biomedical Sciences, Chang Gung University Tao-Yuan, Taiwan.
4
Department of Internal Medicine, Far Eastern Memorial Hospital Taipei, Taiwan.
5
Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine Taipei, Taiwan.
6
Department of Laboratory Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine Taipei, Taiwan ; Department and Graduate Institute of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University Taipei, Taiwan.
7
Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine Taipei, Taiwan ; Department of Laboratory Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine Taipei, Taiwan.

Abstract

We evaluated the performance of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), the MALDI Bruker Biotyper system (microflex LT; Bruker Daltonik GmbH, Bremen, Germany), on the identification of 50 isolates of clinically encountered molds, including Penicillium marneffei (n = 28), Paecilomyces species (n = 12), Fusarium solani (n = 6), Rhizopus species (n = 3), and Pseudallescheria boydii (n = 1). The isolates were identified to species levels by sequence analysis of the internal transcribed spacer (ITS) regions using primers ITS1 and ITS4. None of the 28 genetically well characterized isolates of P. marneffei were identified as P. marneffei by MALDI-TOF MS, because P. marneffei was not present in either Bruker general library (DB 5627) or Bruker filamentous fungi library V1.0. However, the rate of accurate identification as P. marneffei (score value ≥ 2.000) was 85.7% based on newly created database from one P. marneffei strain (NTUH-3370) by MALDI Biotyper system. Sequencing analysis of these 22 non-P. marneffei isolates of molds revealed seven Paecilomyces variotii, six F. solani, four Paecilomyces lilacinus, and one each of Paecilomyces sinensis, Rhizopus arrhizus, R. oryzae, R. microspores, and P. boydii. Although all the seven P. variotii isolates, four of the six F. solani, two of the four P. lilacinus, and two of the three isolates of Rhizopus species, and the P. boydii isolate had concordant identification results between MALDI-TOF MS and sequencing analysis, the score values of these isolates were all of <1.700. This study indicated that the MALDI Bruker Biotyper is ineffective for identifying P. marneffei and other unusual molds because of the current database limitations. Therefore, it is necessary to continuously update the MALDI-TOF MS databases.

KEYWORDS:

Fusarium solani; Paecilomyces species; Penicillium marneffei; Pseudallescheria boydii; Rhizopus species; matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

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