S4.1d In vitro activity of eight antifungals against 3343 filamentous pathogenic fungi collected during 18 years at the French National Reference Center for invasive mycosis and antifungals
Authors: Garcia-Hermoso Dea , Lanternier Fanny , Dromer Françoise ,   French Mycoses Study Group
Published: September 2022

S4.1 Treatment of rare mold infections in 2021: the role of new and old antifungals, September 22, 2022, 10:30 AM - 12:00 PM

 

Background & Objectives

The NRCMA oversees the surveillance of invasive fungal diseases in France. As part of our expertise, we perform antifungal susceptibility testing based on European Committee on Antimicrobial Susceptibility Testing (EUCAST) methodology on all isolates. The antifungal profiles help us monitor the emergence of resistant isolates, determine the susceptibility pattern of wild-type strains to new antifungals, and in specific cases, determine the relationship between clinical failure and selection/emergence of a less susceptible isolate.

We review the Minimum inhibitory concentrations (MIC) distribution of eight antifungals on clinical isolates of filamentous fungi identified at the NRCMA from 2003 to 2021.

Methods

Species identification was performed by a combination of morphological features and multilocus sequencing. Only strains that produced enough conidia or spores were tested. In vitro susceptibility testing was performed according to the EUCAST procedure. Eight antifungal agents were used: triazoles [itraconazole, voriconazole, posaconazole, isavuconazole (since 2015)], echinocandins (caspofungin, micafungin), amphothericin B, and terbinafine. The concentrations inhibiting 50% (MIC50) and 90% (MIC90) of the isolates were determined for species with at least 5 and 10 isolates, respectively. For Aspergillus fumigatus isolates exhibiting high azole MICs, we sequenced the cyp51A gene for mutation screening.

Results

MICs were obtained for 3343 pathogenic strains. We identified Aspergillus spp. including cryptic species (32%), Fusarium spp. (21%), Mucorales (18%), phaeohyphomycetes (10%), i.e., Alternaria spp., Curvularia spp., Fonsecaea, Exophiala, Phaeoacremonium, rare hyphomycetes (9%), i.e., Rasamsonia, Paecilomyces, Trichoderma, Scopulariopsis. Scedosporium spp. (7%) and emergent pathogens such as Nannizziopsis obscura (1%), dimorphic fungi (1%), or to a less extent basidiomycetous molds. Examples of MIC results are presented in Table 1.

For the nine genera of the order Mucorales, amphotericin B (AmB) exhibited low MICs except for Cunninghamella species and Saksenaea vasiformis. Posaconazole had variable activity depending on the species (high MIC values were observed for Mucor species) while voriconazole and echinocandins had none.

In section Fumigati, amphotericin B MIC values were high due to the intrinsic resistance of cryptic species Aspergillus lentulus and A. udagawae. Other cryptic species were identified such as A. hiratsukae isolates which exhibited low MICs to all antifungals.

Members of Aspergillus section Nidulantes such as A. nidulans and A. quadrilineatus showed variable MICs to caspofungin and amphotericin B.

Among melanized fungi, Alternaria infectoria and A. alternata species group displayed low MICs of all azoles with the exception of voriconazole.

Four Exophiala species were analyzed and had similar azole MICs, E. spinifera being the species with the lowest values.

Multi-drug resistant profiles were observed especially in species belonging to Microascales such as Lomentospora prolificans, Microascus cirrosus, and Scopulariopsis brevicaulis. Members of Fusarium species complexes had predictably high MIC values to all antifungals including isavuconazole. Only Fusarium dimerum species complex had low MICs to amphotericin B.

Further distribution analysis is ongoing. These large datasets provide a baseline for monitoring the emergence of antifungal resistance in our country and supports the fact that MIC determination should be performed for rare/emergent species and also in case of infections due to cryptic species, which would benefit patient management.