Optimization of MALDI-ToF mass spectrometry for yeast identification: a multicenter study

Area of Science:

• Clinical Mycology
• Mass Spectrometry
• Microbial Identification

Background:

• Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS) is a key technique for identifying pathogenic yeasts in clinical laboratories.
• Optimizing MALDI-ToF MS protocols is crucial for accurate and rapid identification of clinically relevant fungal species.

Purpose of the Study:

• To evaluate the performance of different Bruker MALDI-ToF MS protocols for yeast identification.
• To compare the efficacy of two pretreatment methods (rapid formic acid extraction, full extraction) and a direct deposit protocol.
• To assess the impact of target types and spectral databases on identification accuracy.

Main Methods:

• A multicenter study involving ten European laboratories analyzed 1511 yeast isolates.
• Three protocols were tested: rapid formic acid extraction, full extraction, and direct deposit.
• Identification performance was evaluated using ground-steel, polished-steel, and biotargets, and Bruker and MSI databases.

Main Results:

• The full extraction method demonstrated superior performance compared to the other protocols.
• The direct deposit protocol was found to be inappropriate for yeast identification.
• Rapid formic acid extraction yielded variable results, dependent on target, database, and threshold settings.

Conclusions:

• The full extraction method, when optimized with appropriate targets and databases, ensures accurate and reliable yeast identification via MALDI-ToF MS.
• Careful selection of extraction method, target, database, and threshold is essential for robust clinical mycology diagnostics.
• Even with widely used polished-steel targets, full extraction remains the preferred method for optimal MALDI-ToF MS identification rates.