A MALDI-TOF MS-based discriminant model to distinguish azole-resistant Aspergillus fumigatus strains

Abstract

Abstract Aspergillus fumigatus is the major causative agent of aspergillosis in immunosuppressed hosts and patients with chronic pulmonary diseases. Recently, azole resistance of this fungus has become a problem worldwide; thus, rapid detection of resistant strains is desirable in clinical practice. In this study, we established a matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) combined with multivariate and discriminant analysis to detect azole-resistant A. fumigatus strains. The score plot from a partial least squares discriminant analysis clearly separated resistant and susceptible strains, regardless of the culture period. The discriminant analysis using the support-vector machine algorithm based on a dataset for strains cultured on potato dextrose agar for 3 days showed the best performance, with a correct answer rate of 84.75–99.85%. We found a MS peak (4359.5 m/z) specific to some azole-resistant strains with a 34-bp tandem repeat in the promoter region of cyp51A. These tandem repeat strains are extremely rare in Japan. Instead, most resistant strains in Japan have point mutations in cyp51A. No specific biomarker for strains with point mutations was found, but it was possible to detect these resistant strains using a model for point-mutation strains.