The Molecular Identification and Antifungal Susceptibility of Clinical Isolates of Aspergillus Section Flavi from Three French Hospitals

Abstract

(1) Background: Aspergillus flavus is a cosmopolitan mold with medical, veterinary, and agronomic concerns. Its morphological similarity to other cryptic species of the Flavi section requires molecular identification techniques that are not routinely performed. For clinical isolates of Aspergillus section Flavi, we present the molecular identification, susceptibility to six antifungal agents, and clinical context of source patients. (2) Methods: One hundred forty fungal clinical isolates were included in the study. These isolates, recovered over a 15-year period (2001–2015), were identified based on their morphological characteristics as belonging to section Flavi. After the subculture, sequencing of a part of the β-tubulin and calmodulin genes was performed, and resistance to azole antifungals was screened on agar plates containing itraconazole and voriconazole. Minimum inhibitory concentrations were determined for 120 isolates by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) broth microdilution method. (3) Results: Partial β-tubulin and calmodulin sequences analysis showed that 138/140 isolates were A. flavus sensu stricto, 1 isolate was A. parasiticus/sojae, and 1 was A. nomiae. Many of the isolates came from samples collected in the context of respiratory tract colonization. Among probable or proven aspergillosis, respiratory infections were the most frequent, followed by ENT infections. Antifungal susceptibility testing was available for isolates (n = 120, all A. flavus ss) from one hospital. The MIC range (geometric mean MIC) in mg/L was 0.5–8 (0.77), 0.5–8 (1.03), 0.125–2 (0.25), 0.03–2 (0.22), 0.25–8 (1.91), and 0.03–0.125 (0.061) for voriconazole, isavuconazole, itraconazole, posaconazole, amphotericin B, and caspofungin, respectively. Two (1.67%) isolates showed resistance to isavuconazole according to current EUCAST breakpoints with MICs at 8 mg/L for isavuconazole and voriconazole. One of these two isolates was also resistant to itraconazole with MIC at 2 mg/L. (4) Conclusions: The present characterization of a large collection of Aspergillus belonging to the Flavi section confirmed that A. flavus ss is the predominant species. It is mainly implicated in respiratory and ENT infections. The emergence of resistance highlights the need to perform susceptibility tests on section Flavi isolates.

Azole resistance in Aspergillus flavus and associated fitness cost

“…in 2020 2 . All the strains had been identified in a previous study, 22 except strain GRE150, identified in the present study.…”

“…DNA extraction and molecular identification were performed as previously described 22 . Identification was performed by partial sequencing of the β‐tubulin and calmodulin genes and comparison to the sequence of the type strains of each the cryptic species within the Flavi section based on the most recent taxonomic revision of the Flavi section published by Houbraken et al.…”

Bioprospecting of endophytic fungi from semidesert candelilla (Euphorbia antisyphiliticaZucc): Potential for extracellular enzyme production

“…These genes contain conserved sequences common to all fungi; however, for some genera, this target does not allow the identification of all the species that compose it, making it necessary to search for other targets with greater resolving power. Different gene regions, such as beta-tubulin, have been used that show potential for the identification of fungi such as N. crassa and other genera such as Colletotrichum and Aspergillus with DNA sequence analysis [42][43][44][45][46].…”

First reported aflatoxigenic isolates of Aspergillus flavus in agroforestry systems in Buenaventura, Valle del Cauca-Colombia

“…Aspergillus section Flavi comprises several species that are frequently found in agricultural crops. Certain species within this section can produce aflatoxins (Podgórska-Kryszczuk, 2023), while others are known to cause aspergillosis and respiratory allergies in humans (Djenontin et al, 2023). Aspergillus flavus, one of the most significant species in this section, is a major producer of aflatoxins (Bertechini-Faria et al, 2017).…”

“…A. flavus is a species that presents challenges due to its capacity to grow on diverse substrates in varying environmental conditions and produce numerous spores that can survive under extreme circumstances (Segura-Palacios et al, 2021). It is frequently found in tropical and subtropical regions where the temperature ranges from 28-37°C and the relative humidity is above 85% (Okayo et al, 2020;Djenontin et al, 2023). This species is commonly found in crops such as maize, soybean, peanuts, pistachios, cottonseed, sunflower seeds, and rice (Douksouna et al, 2019;Segura-Palacios et al, 2021).…”