Validation of a modified algorithm for the identification of yeast isolates using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS)
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Optimising antifungal treatment requires the fast and species-specific identification of yeast isolates. We evaluated a modified protocol for the rapid identification of clinical yeast isolates using matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) technology. First, we evaluated a simplified extraction procedure using 54 clinical yeast isolates. Second, we validated a new protocol with this simplified extraction procedure and lower identification threshold by analysing 167 isolates with either MALDI-TOF or conventional identification techniques. MALDI-TOF analysis with both the standard and short extraction procedure yielded identical identification results, although the log-scores were lower with the latter. With the modified protocol, 163/167 (97.6%) isolates showed a correct identification as compared to conventional identification techniques. A total of 135 out of the 163 (82.8%) correct identifications showed log-scores above 1.7, which we considered as the minimum log-score for secure species identification. The rapid identification of clinical yeast isolates is crucial in patient management. The MALDI-TOF technique using a short extraction procedure can be an alternative for the labourious standard procedure, although the log-scores will be lower. The identification of clinical yeast isolates with the modified protocol is a practical and accurate alternative for conventional identification techniques. If the isolate shows a log-score below 1.7, the standard extraction procedure should be used.
KeywordsCandida Species Yeast Isolate Identification Threshold Yeast Identification Simplify Extraction Procedure
We thank all laboratory technicians at the clinical microbiology laboratory of ZNA Middelheim Hospital for their hard work with the sample analysis. Further we thank Dr. Van Esbroeck at the Institute of Tropical Medicine Antwerp, the staff at the ZNA Stuivenberg Hospital and the staff at the clinical microbiology laboratory of GZA St.Vincentius for their help in sample collection.
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