Susceptibility of environmental versus clinical strains of pathogenic Aspergillus

The objective of this study was to compare the antifungal susceptibility profiles of 307 environmental strains and 139 clinical isolates of Aspergillus belonging to six different species. Clinical and environmental strains with minimal inhibitory concentrations (MICs) or minimal effective concentrations ≥4 μg/mL to amphotericin B (AMB), itraconazole (ITC), voriconazole and caspofungin were seldom detected. However, the susceptibility profile of environmental Aspergillus non-fumigatus strains suggests a native reduced susceptibility of Aspergillus flavus and Aspergillus terreus to AMB. A single environmental strain of Aspergillus nidulans showed high in vitro resistance (MIC ≥ 16 μg/mL) to ITC. Aspergillus niger showed significantly higher MIC values to ITC compared with the other Aspergillus spp. Conversely, A. fumigatus and Aspergillus glaucus showed higher susceptible profiles to the antifungals. Definition of the breakpoints for the antifungal agents remains urgent. The relationship between the susceptibility pattern and the pathogenic potential also deserves more attention, particularly with regard to non-fumigatus species.