Antifungal susceptibility patterns for Aspergillus, Scedosporium and Exophiala isolates recovered from cystic fibrosis patients against amphotericin B, and three triazoles and their impact after long term therapies.

Abstract

In cystic fibrosis (CF) patients, fungal colonization of the respiratory tract is frequently found. Aspergillus fumigatus, Scedosporium genus and Exophiala dermatitidis are the most commonly isolated molds from the respiratory tract secretions of patients with this genetic disorder. The aim of this 5-year surveillance study was to identify trends in species distribution and susceptibility patterns of 212 mold strains identified as Aspergillus spp., Scedosporium spp. and Exophiala spp., isolated from sputum of 63 CF patients who received long term therapy with itraconazole and/or voriconazole. The Aspergillus spp. isolates were identified as members of the sections Fumigati (n=130), Flavi (n=22), Terrei (n=20), Nigri (n=8), Nidulantes (n=1) and Usti (n=1). Among the 16 species of the genus Scedosporium, 9 were S. apiospermum, 3 S. aurantiacum and 4 S. boydii. Among the 14 Exophiala species, all were molecularly identified as E. dermatitidis. Overall, 94% (15/16) of Scedosporium spp., 50% (7/14) of E. dermatitidis, and 7.7% (14/182) of Aspergillus spp. strains, showed high MIC values (≥ 8 µg/ml) for at least one antifungal. Particularly, 8.9% (19/212) of isolates showed high MIC values to amphotericin B, 11.7% (25/212) itraconazole, 4.2% (9/212) to voriconazole and 3.3% (7/212) to posaconazole. In some cases, such as some A. fumigatus and E. dermatitidis isolates recovered from the same patient, susceptibility to antifungal azoles decreased over time. We show that the use of azoles for a long time in CF patients causes the selection/isolation of mold strains with higher MIC values.