Triazole antifungal drugs such as itraconazole, posaconazole and voriconazole are the mainstay of therapy in the management and prophylaxis of aspergillosis. However, in recent years, triazole-resistant clinical isolates of Aspergillus fumigatus have emerged in Europe (the Netherlands, Denmark, Spain, UK, Belgium, Germany and France) and Asia (China, India) resulting in several cases of therapeutic failure caused by triazole-resistant A. fumigatus. Azole resistance may develop in patients who are treated with long-term azole therapy or may develop in the environment through the exposure of the fungus to the azole fungicides used in agriculture.

In the present study, we investigated the presence of azole resistance in environmental and clinical A. fumigatus isolated both from hospital surroundings area and infected patients.

In vitro antifungal susceptibility testing has shown high MICs of itraconazole (>16mg/L) and voriconazole (>8mg/L). The TR34/L98H mutation was the only resistance mechanism with no mutation in G54, M220, G138C, T289A, Y121F and G432C. Azole-resistant A. fumigatus isolates had the same TR34/L98H STRAf genotype with Netherlands and India. It is emphasized that routine resistance surveillance studies focusing on environmental and clinical samples are warranted to yield the true prevalence of azole resistance in A. fumigatus in Iran.

The widespread application of triazole fungicides in the environment in Iran could have contributed to the emergence of environmental azole-resistant A. fumigatus. Given the emergence of azole resistance in environmental strains, continued surveillance of resistance in clinical A. fumigatus strains in Iran is desirable for successful therapy of aspergillosis. Furthermore, the need for enhanced understanding of the evolution of azole resistance and measures to prevent the emergence of multiple-azole-resistant A. fumigatus strains in countries using fungicides can hardly be over-emphasized.