Application of whole genome sequencing analysis to detect the azole-resistance mechanisms in Aspergillus fumigatus in a global surveillance programme

Mariana Castanheira, Andrew P Davis, Lalitagauri M. Deshpande, Paul R. Rhomberg, Michael A. Pfaller

Author address: 

JMI Laboratories, North Liberty, United States


Abstract third-party references: This study was performed by JMI Laboratories and supported by Pfizer, Inc., which included funding for services related to preparing this abstract.

Background: Azole-resistance is uncommon among A. fumigatus clinical isolates and is mainly associated with mutations in cyp51A and its promoter region or its homologue cyp51B. We evaluated 35 A. fumigatus isolates nonwildtype (NWT) to isavuconazole, itraconazole or voriconazole collected during a 2-year surveillance using whole genome sequencing (WGS) to detect alterations in the genes involved in the ergosterol biosynthesis and others associated with azole resistance.

Materials/methods: Among 297 A. fumigatus isolates collected worldwide in 2017-2018, 35 isolates displayed NWT MIC values to isavuconazole, itraconazole or voriconazole when tested by the CLSI reference broth microdilution method. These 35 isolates were submitted to WGS and data analysis using previously described tools.

Results: Among the 35 NWT isolates, 29 were NWT to isavuconazole, 16 to itraconazole and 9 to voriconazole (M59Ed2 criteria). A total of 9 isolates carried Cyp51A L98H/TR34 alterations: 8 from different patients hospitalized in a single Italian hospital and 1 from Belgium. All 9 Cyp51A L98H/TR34 isolates were NWT to both isavuconazole and itraconazole and 8 were voriconazoleNWT. Cyp51A L98H/TR34 isolates belonged to sequence type (ST)6, ST26 or its single loci variant ST1. None of the other azoleNWT isolates belonged to these STs. Five isolates were NWT to itraconazole alone, 3 of 5 containing Cyp51A I242V. A Cyp51B Q42L mutation was detected in 3 isolates, 1 voriconazole-NWT and 2 isavuconazole-NWT of which 1 also harboured multiple mutations in Cyp51A (F46Y, M172V, N248T, D255E and E427K). Two isolates NWT to isavuconazole and itraconazole possessed F46Y, M172V, E427K ± N248T, D255E. Among the 29 isavuconazole-NWT strains, 16 contained alterations in other ergosterol biosynthesis or efflux genes that have not been implicated in azole resistance.

Conclusions: Cyp51A L98H/TR34 were noted in 9 isolates that were NWT to both isavuconazole and itraconazole and 8 were NWT to all azoles tested. Other alterations, including F46Y, M172V, E427K±N248T, D255E that have been reported in 10% of the azole-NWT isolates worldwide, were only detected in isolates NWT to isavuconazole and itraconazole. Mutation driven azole resistance mechanisms were not detected in 16 isolates displaying isavuconazole-NWT MIC values that had WT MIC values for other azoles.

Presenter email address: [email protected]


abstract No: 


Full conference title: 

European Congress of Clinical Microbiology and Infectious Diseases 2020
    • ECCMID 30th (2020)