Susceptibility to five antifungals of Aspergillus fumigatus strains isolated from chronically colonised cystic fibrosis patients receiving azole therapy

Exposure of Aspergillus fumigatus to stressful antifungal therapies may result in decreased susceptibility. The aim of the present work was to evaluate the susceptibility to azole and non-azole antifungals of 159 isolates of A. fumigatus collected from cystic fibrosis (CF) patients receiving azole antifungal therapy. The genetic diversity of the fungal isolates was assessed using microsatellite genotyping, and some strains were found in patient's sputum samples more than 4 years apart. No resistant isolates [minimal inhibitory concentration (MIC)/minimal effective concentration (MEC) ≥4 μg/mL] were identified to the antifungals amphotericin B, caspofungin, itraconazole and voriconazole. A single A. fumigatus isolate was identified outside of the epidemiological cut-off of 0.25 μg/mL for posaconazole. Susceptibility of the recurrent isolates was in agreement with the susceptibility of the first isolate identified (100% essential agreement). Even after azole exposure, several recurrent A. fumigatus strains were detected in the subsequent sputum samples. Development of resistance in A. fumigatus to antifungals appears to be rare amongst CF patients. However, it remains crucial to evaluate the importance of antifungal agents for allergic fungal diseases.