Author:
J Lucio1*, I Gonzalez-Jimenez1, E Mellado1,2
Author address:
1Mycology Reference Laboratory, National Centre for Microbiology, Instituto de Salud Carlos III (ISCIII), Majadahonda (Madrid), Spain
2Spanish Network for Research in Infectious Diseases, Instituto de Salud Carlos III (ISCIII), Majadahonda (Madrid), Spain
Full conference title:
10th Advances Against Aspergillosis and Mucormycosis
Date: 2 February 2022
Abstract:
Purpose:
Aspergillus fumigatus is a worldwide fungal pathogen that causes a highly lethal opportunistic infection in immunocompromised individuals. Azole drugs, targeting Cyp51A, are the first line antifungal treatment for aspergillosis; however, the rising isolation of azole-resistant A. fumigatus strains in the last decade imposes a great challenge in the management of patients with aspergillosis. The continuous exposure of A. fumigatus to environmental fungicides, such as demethylase inhibitors (DMIs), used for crop protection against other fungal plant pathogens, is believed to be selecting multi-drug resistant strains. The repeated use of fungicides of single mode of action is leading to the selection of mutations in the genes encoding the target site protein decreasing the effectiveness of the antifungals. This situation applies, not only to a diverse amount of fungal plant pathogens but also to non-targeted fungi, including A. fumigatus, via the selection of antifungal resistant strains that are unaffected by multiple fungicides favoring their spread and dissemination. Recently, we described that azole resistant A. fumigatus bearing the TR34/L98H Cyp51A mutations showed resistance to several other environmental antifungal single sites classes such as benzimidazoles (MBCs), strobilurins (QoIs) and succinate dehydrogenase inhibitors (SDHIs). In this study, a collection of azole-susceptible and resistant A. fumigatus strains with different mutations in Cyp51A, β-tubulin, cytochrome b and SdhB were tested against dicarboximide and phenylpirrole antifungals.
Methods:
To carry out this study we selected 60 A. fumigatus isolates, 19 azole-susceptible strains and 41 azole-resistant strains, harboring different mutations in Cyp51A, β-tubulin, cytochrome b and SdhB. One antifungal compound from each antifungal class was tested: iprodione (dicarboximides) and fludioxonil (phenylpirroles). Susceptibility testing was assessed spotting 3 µL, containing 3×104 spores, on three sets of minimal medium plates, one of them containing 8 mg/L fludioxonil, another plate containing 32 mg/L iprodione and a growth control plate. The target gene bos1 was PCR amplified and sequenced. In addition, the bos1 gene was analyzed in a collection of 163 A. fumigatus genomes from different countries compromising a variety of azole resistant mechanisms.
Results:
All strains with iprodione resistance (> 32 mg/L) had a point mutation (I399N) in the HAMP 3 domain of class III histidine-kinase Bos1 coding region. None of them was resistant to fludioxonil. Other mutations found in the HAMP domains (D371Y and Q423K) were not related to iprodione resistance. The phylogenetic tree showed that A. fumigatus strains harboring
iprodione resistance grouped together in one sub-clusters where all strains were azole resistant (TR34/L98H) and have a variety of different patterns of cross-resistance to other fungicides such as DMIs, MBCs, QoIs and SDHIs.
Conclusion:
The mutation I399N is responsible for A. fumigatus resistance to the dicarboximide iprodione but not to the phenylpirrole fludioxonil. A strong association between the azole resistance mechanism TR34/L98H and the resistance phenotype to several environmental fungicides reassured the environmental resistance origin of these resistant strains. These results suggests a selection of multi-drug resistant strains in crops that show cross-resistance with clinical azoles. Further research to understand the origin and spread of A. fumigatus azole-resistant strains is needed.
Abstract Number: 52
Conference Year: 2022
Link to conference website: https://aaam2022.org/
URL Conference abstract: