Rapid identification of Candida species by MALDI-TOF technology

Objectives and background: Rapid identification of yeast isolates is important in order to adjust the antifungal treatment and to reduce patient morbidity and mortality. In this study we investigate whether Matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) can 1) replace current routine methods in first line identification of Candida and 2) examine differences in generated results by two mass spectrometry instruments situated in two routine laboratory settings and 3) measure time from entry of sample in the instrument to results. In East Denmark, the Microflex LT (Bruker Daltonics, Germany) and in West Denmark, the Vitek® MS (bioMérieux, France). Method: Retrospective analysis of Candida isolates with identification in parallel by two MALDI-TOF instruments and API. API 20 C AUX (bioMérieux, France) was used as the standard method. Results: 93 isolates were examined on Microflex LT with the Biotyper 2.0 software according to the manufacturer´s manual. 96% (89/93) were identified to species level and 2% (2/93) were identified to genus level. Furthermore 2% (2/93) were identified as Candida robusta (teleomorph stage) by the Biotyper software and Saccharomyces cerevisae (anamorph stage) by API 32. A routine measurement of 18 samples takes 10 minutes from entry to the final result. The Vitek® MS Acquisition station connected to Myla™ V.2.4.0-1, using a sample preparation as recommended by the manufacturer, identified 91% (85/93) of isolates to species level, 2% to genus level, 2% were not identified as findings did not comply with the database, 2% did not display results and 2 % showed discrepancies. Routine measurements of 18 spots from entry to final result take 40 minutes. Conclusion: In our study, MALDI-TOF MS can replace current used methods in the clinical Microbiology laboratories in first line identification of Candida. Both software systems are unable to distinguish Candida albicans/dubliniensis. Time used from acquisition of sample to results favour the Microflex LT with the Biotyper Software although the extraction protocol of fungi is more time consuming than the protocol recommended by bioMérieux.