Azole resistance among clinical Aspergillus fumigatus species complex isolates in Greece: first detection of TR46-mediated resistance and azole-resistant cryptic species
Maria Siopi, Margarita Vargiami, Maria-Ioanna Beredaki, Aristea Velegraki, Levantia Zachariadou, Emmanuel Roilides, Georgios Chamilos, Stavroula Antonopoulou, Lemonia Skoura, Ana Alastruey-Izquierdo, Spyros Pournaras, Joseph MeletiadisAbstract
Objectives
To assess the prevalence of antifungal resistance among clinical Aspergillus fumigatus species complex (SC) isolates in Greece, focusing on azole resistance and its underlying molecular mechanisms.
Methods
A total of 249 clinical A. fumigatus SC isolates were collected from geographically distinct centres across Greece. Antifungal susceptibility testing (AFST) was conducted according to EUCAST guidelines. Cryptic species and azole-resistant A. fumigatus (ARAf) isolates underwent confirmatory molecular identification. ARAf sensu stricto (SS) isolates were further analysed by CYP51A gene and promoter sequencing to detect resistance-associated mutations.
Results
Most isolates (246/249; 99%) were identified as A. fumigatus SS, while three isolates were molecularly identified as A. fumigatiaffinis, A. lentulus and A. pseudoviridinutans. Amphotericin B and echinocandins demonstrated good in vitro activity against A. fumigatus SS, whereas posaconazole was the most active azole in vitro. Cryptic species exhibited reduced susceptibility compared with A. fumigatus SS. Two isolates (1%; A. fumigatiaffinis and A. lentulus) were amphotericin B-resistant. Five isolates (2%) were ARAf, including all three cryptic species (from patients with chronic pulmonary aspergillosis; one pan-ARAf) and two A. fumigatus SS strains. One ARAf SS isolate (from a cystic fibrosis patient) was pan-ARAf and harboured the TR46/Y121F/T289A CYP51A mutation, while the second (from an ICU patient) displayed resistance to itraconazole, isavuconazole and posaconazole without detectable CYP51A mutations.
Conclusions
Although the clinical ARAf rate remains low in Greece, the first detection of pan-azole resistance associated with environmentally driven resistance mechanisms or cryptic species highlights the importance of surveillance, accurate species identification and routine AFST.