Trends of Azole-Resistant Aspergillus Fumigatus Susceptibility Over 12 Years from a German ECMM Excellence Center

Numbers of infections with azole-resistant Aspergillus fumigatus (ARAf) were rising in the last decades. We assessed ARAf susceptibility trends towards five antifungal agents (amphotericin B (AMB), itraconazole (ITR), voriconazole (VCZ), olorofim (OLO) and manogepix (MGX)) over twelve years in a German Excellence Center for Medical Mycology (ECMM). In addition, underlying mutations were studied and correlated with trends in minimum inhibitory concentration (MIC). Broth microdilution (BMD) was performed following EUCAST guidelines for 143 clinical ARAf isolates collected between the years 2011 and 2022 in a West German tertiary care centre. BMD was carried out for all antifungal agents in the following concentration ranges: 0.016-8 mg/L for AMB, ITR and VCZ as well as 0.001-0.5 mg/L for OLO and 0.004-2 mg/L for MGX. Molecular assays on mutations associated with antifungal resistance were performed for all 143 isolates (AsperGenius (R) 1.0, Pathonostics, Maastricht, The Netherlands) and for a total of ten non TR34/L98H and TR46/Y121F/T289A mutated ARAf isolates additional cyp51A sequencing was carried out. For all isolates, microdilution revealed a MIC50 of > 8 mg/L for ITR, 4 mg/L for VCZ, 0.03 mg/L for OLO, 0.016 mg/L for MGX, and 0.5 mg/L for AMB. Considering EUCAST breakpoints, 97.9% of the strains (n = 140) were resistant to VCZ, 1.4% (n = 2) towards AMB and 92.3% towards ITR (n = 132). Molecular assays revealed 123 (86%) isolates with the azole resistance underlying mutation TR34/L98H, 10 (7%) with a TR46/Y121F/T289A mutation and 10 (7%) with other cyp51A mutations. A comparison of triazole MICs of isolates collected from 2011 to 2019 with the MICs of isolates collected between 2020 and 2022 revealed no significant differences for itraconazole (p = 0.543) and for voriconazole (p = 0.148),with a trend of increased geometric mean for ITR and VCZ MICs over time. MICs for OLO and MGX did not significantly differ between isolates with the distinct azole-resistance underlying mutations. Before 2016, the azole resistance underlying mutations were mainly TR34/L98H, but the portion of isolates with TR46/Y121F/T289A and other Cyp51A mutated isolates increased afterwards. We showed almost stable MICs for ITR and VCZ over twelve years in ARAf isolates from West Germany while occurring azole resistance underlying mutations varied with an increase in the proportion of TR46/Y121F/T289A and other Cyp51A mutations after 2016.