Background and purpose: Invasive aspergillosis (IA) is a leading cause of morbidity and mortality in patients with decreased immune status. Aspergillus flavus is the second most common species causing invasive aspergillosis after A. fumigatus. According to limited information on the antifungal susceptibility test against A. flavus in Iran, in this study we aimed at evaluating the antifungal susceptibility of two antifungal agents including itraconazole and voriconazole against clinical and environmental isolates of A. flavus.

Materials and methods: Four hundred clinical and environmental samples were collected from Mazandaran, Tehran and Khorasan Razavi provinces. The identification of A. flavus isolates were confirmed by sequencing of β-tubulin gene. The MICs of itraconazole and voriconazole for all isolates of A. flavus were determined by the guidelines proposed by Clinical and Laboratory Standards Institute (CLSI) M38-A2 for filamentous fungi.

Results: Ninety isolates of A. flavus were identified from clinical (n=30) and environmental (n=60) samples. MIC results of all A. flavus isolates showed susceptibility to antifungal agents, except for two environmental isolates that demonstrated MIC= 2 μg/ml for itraconazole. MIC₅₀, MIC₉₀ and Geometric mean of itraconazole for A. flavus isolates were 0.25, 0.5, and 0.21 μg/ml, respectively. The MIC₅₀, MIC₉₀ and Geometric mean of voriconazole were 0.25, 0.5 and 0.27 μg/ml, respectively.

Conclusion: In comparison to determined epidemiological cutoff value of A. flavus, our data have shown a probable resistance in two isolates of A. flavus against itraconazole which draws attention on emergence of full resistance A. flavus isolates from Iran.