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Genus-level identification of dermatophytes by MALDI-TOF MS after 2 days of colony growth.
Journal article

Genus-level identification of dermatophytes by MALDI-TOF MS after 2 days of colony growth.

  • Intra J Department of Laboratory Medicine, University of Milano-Bicocca, Desio Hospital, Desio, MB, Italy.
  • Sarto C Department of Laboratory Medicine, University of Milano-Bicocca, Desio Hospital, Desio, MB, Italy.
  • Tiberti N Translational Biomarker Group, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
  • Besana S Department of Laboratory Medicine, University of Milano-Bicocca, Desio Hospital, Desio, MB, Italy.
  • Savarino C Department of Laboratory Medicine, University of Milano-Bicocca, Desio Hospital, Desio, MB, Italy.
  • Brambilla P Department of Laboratory Medicine, University of Milano-Bicocca, Desio Hospital, Desio, MB, Italy.
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  • 2018-04-22
Published in:
  • Letters in applied microbiology. - 2018
MALDI-TOF MS
dermatophyte
identification
incubation time
rapid method
Acetonitriles
Arthrodermataceae
Dermatomycoses
Epidermophyton
Ethanol
Formates
Humans
Liquid-Liquid Extraction
Microsporum
Mycological Typing Techniques
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
Trichophyton
Workflow
English Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) is becoming a popular technology in clinical microbiology. It is a fast and highly specific method for the routine identification of micro-organisms. In this study, we evaluated the suitability of dermatophyte identification after only 2 days of colony growth using MALDI-TOF MS. Two protein extraction protocols were also evaluated consisting of either formic acid alone or of ethanol-formic acid-acetonitrile to achieve a complete protein extraction. Morphology-based techniques were used as the diagnostic standard methods and MALDI-TOF MS results were obtained using the manufacturer's spectral library. Using the formic acid protein extraction protocol after 2 days of colony growth, 70 and 46% of dermatophytes were properly identified at the genus and species-level respectively. The addition of ethanol-formic acid-acetonitrile extraction protocol increased the identification to 90 and 62%. Based on our observations, we propose a two-step workflow for the fast and reliable identification of dermatophytes after only 2 days of colony growth. This flow chart consists of a first direct deposition procedure with the addition of formic acid, followed by a complete protein extraction when dermatophyte identification is not successful.


SIGNIFICANCE AND IMPACT OF THE STUDY
In this study, a two-step workflow for the identification of clinical dermatophytes using MALDI-TOF analysis and commercially available spectral library was developed. The workflow consists of an initial direct deposition of the sample on the MALDI plate and formic acid protein extraction at 2 days of growth culture; if dermatophyte identification is not successful, a complete protein extraction using ethanol-formic acid-acetonitrile is subsequently performed. Using this workflow, the correct isolate identifications increase up to 90%; of these, 27% are identified at the genus-level, providing sufficient information to start an antifungal treatment. The method here proposed represents a fast and useful approach to differentiate dermatophytes grown in culture.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/252121
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