Detection of azole resistance in Aspergillus fumigatus complex isolates using MALDI-TOF mass spectrometry
Clin Microbiol Infect. 2021 Jun 17:S1198-743X(21)00322-0. doi: 10.1016/j.cmi.2021.06.005. Online ahead of print.
OBJECTIVES: The main goal of this study was to accurately detect azole resistance in species of the Aspergillus fumigatus complex by MALDI-TOF MS.
METHODS: Identification of isolates (n=868) was done with MALDI-TOF MS using both commercial and in-house libraries. To determine azole susceptibility, the EUCAST E.Def. 9.3.2 method was applied as the gold standard. Identification of resistant isolates was confirmed by DNA sequence analysis. Protein spectra obtained by MALDI-TOF MS were analyzed to differentiate species within the A. fumigatus complex and detect azole-resistant A. fumigatus sensu stricto isolates.
RESULTS: Correct discrimination of A. fumigatus sensu stricto from cryptic species was accomplished in 100% of the cases applying Principal Component Analysis (PCA) to protein spectra generated by MALDI-TOF MS. Furthermore, a specific peak (4,586 m/z) was found to only be present in cryptic species. The application of Partial Least Squares Discriminant Analysis allowed 98.43% (±0.038) discrimination between susceptible and azole-resistant A. fumigatus sensu stricto isolates. Finally, based on PLS and SVM, A. fumigatus sensu stricto isolates with different cyp51A gene mutations were correctly clustered in 91.5% of the cases.
CONCLUSIONS: MALDI-TOF MS combined with peak analysis is a novel tool that allows the differentiation of A. fumigatus sensu stricto from other species within the A. fumigatus complex, as well as to detect azole-resistant A. fumigatus sensu stricto. Although further studies are still needed, the results here reported show the great potential of MALDI-TOF and machine learning for rapid detection of azole resistant Aspergillus fumigatus isolates from clinical origin.