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Antimicrob Agents Chemother. 2019 Aug 26. pii: AAC.00632-19. doi: 10.1128/AAC.00632-19. [Epub ahead of print]

Cyp51A mutations, Extrolite Profiles and Antifungal Susceptibility in Clinical and Environmental Isolates of the Aspergillus viridinutans Species Complex.

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Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, NSW, Australia
Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark.
Department of Medical Microbiology and Infectious Diseases, Canisius Wilhelmina Hospital (CWZ), Nijmegen, the Netherlands.
Center of Expertise in Mycology Radboudumc/CWZ, Nijmegen, the Netherlands.
Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands.
Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, the Netherlands.
Faculty of Pharmacy, The University of Sydney, New South Wales, Australia.
National Mycology Reference Centre, Microbiology and Infectious Diseases, SA Pathology, SA, Australia.
Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, NSW, Australia.
Marie Bashir Institute of Biosecurity and Infectious Diseases, The University of Sydney, NSW, Australia.


The past decade has seen an increase in aspergillosis in humans and animals due to Aspergillus viridinutans species complex members. Azole resistance is common to these infections, carrying a poor prognosis. Cyp51A gene mutations are the main cause of acquired azole resistance in Aspergillus fumigatus This study aimed to determine if azole-resistant phenotype in A. viridinutans complex members is associated with cyp51A mutations or extrolite profiles. The cyp51A gene of clinical and environmental isolates was amplified using novel primers, antifungal susceptibility was tested using Clinical Laboratory Standards Institute methodology and extrolite profiling was performed using agar plug extraction. Very high azole minimum inhibitory concentrations (MICs) were detected in 84% of the isolates (31/37). MICs of newer antifungals luliconazole and olorofim (F901318) were low for all isolates. Cyp51A sequences revealed 113 non-synonymous mutations compared to wild-type A. fumigatus M172A/V and D255G, previously associated with A. fumigatus azole resistance, were common amongst all isolates but were not correlated with azole MICs. Two environmental isolates with non-susceptibility to itraconazole, and high MICs of voriconazole and isavuconazole, harboured G138C, previously associated with azole-resistant A. fumigatus Some novel mutations were only identified amongst isolates with high azole MICs. However, cyp51A homology modelling did not cause a significant protein structure change for these mutations. There was no correlation between extrolite patterns and susceptibility. For A. viridinutans complex isolates, cyp51A mutations and the extrolites they produced were not major causes of antifungal resistance. Luliconazole and olorofim show promise for treating azole-resistant infections caused by these cryptic species.

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