Genotyping and Antifungal Susceptibility Testing of <i>Aspergillus flavus</i> Isolated from Clinical Specimens

Background: After Aspergillus fumigatus, A. flavus is the second leading cause of invasive and non-invasive aspergillosis. These fungi are of significant epidemiological importance in provinces with dry and hot climates. Objectives: In the present study, antifungal susceptibility testing (AFST) and genotyping of sixty-five A. flavus clinical isolates originating from patients in Mazandaran and Tehran were performed. Methods: Antifungal susceptibility testing of 65 clinical isolates of A. flavus was conducted against amphotericin B (AMB), itraconazole (ITR), voriconazole (VOR), posaconazole (POS), isavuconazole (ISA), luliconazole (LUL), lanoconazole (LAN), and 5-fluorocytosine according to the Clinical Laboratory Standards Institute (CLSI) method (M38-A2). The minimum inhibitory concentrations (MICs) were determined for each antifungal drug against all strains. Additionally, microsatellite typing using six variable number tandem repeat (VNTR) markers was performed to assess the genetic diversity and potential relationships among the clinical strains. Results: Luliconazole had the lowest geometric mean MIC (0.020 μg/mL), followed by LAN (0.021 μg/mL), POS (0.089 μg/mL), ISA (0.115 μg/mL), ITR (0.220 μg/mL), VOR (0.244 μg/mL), AMB (0.870 μg/mL), and 5-fluorocytosine (58.76 μg/mL). Microsatellite typing revealed sixty-five distinct sequence genotypes. Statistically, there was no significant relationship between genotypes and AFST profiles (P ≥ 0.05). Conclusions: Luliconazole and lanoconazole demonstrated the greatest in vitro activity among all tested antifungals. However, most A. flavus strains exhibited reduced sensitivity to AMB. Microsatellite genotyping indicated no genetic similarity among the clinical strains, revealing high genetic diversity among A. flavus isolates obtained from clinical samples.