International Journal of Antimicrobial Agents 29 (2007) 108–111 Short communication Susceptibility of environmental versus clinical strains of pathogenic Aspergillus Ricardo Araujo a,* , Cidalia Pina-Vaz a , Acacio Gonc ¸alves Rodrigues a,b a Department of Microbiology, Faculty of Medicine, University of Porto, Alameda Prof. Hernani Monteiro, 4200-319 Porto, Portugal b Burn Unit, Department of Plastic and Reconstruction Surgery, Hospital S. Joao, Porto, Portugal Received 14 August 2006; accepted 26 September 2006 Abstract 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 g/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 g/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. © 2006 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved. Keywords: Aspergillus fumigatus; Aspergillus ﬂavus; Amphotericin B; Itraconazole; Voriconazole; Caspofungin; Susceptibility testing 1. Introduction Nowadays, invasive aspergillosis is an increasing fun- gal infection in intensive care, transplant and burn units. Immunosuppression, particularly persistent neutropenia or high-dose corticosteroids, represents a serious risk factor associated with invasive Aspergillus infections [1]. Minimal inhibitory concentrations (MICs) remain the most valuable laboratory tool available to predict resistance and to select the best alternative for antifungal treatment. The full rela- tionship between antifungal susceptibility and pathogenic potential remains unknown, however reduced susceptibility of strains to antifungals has been shown to be closely related to higher mortality rates in murine models [2,3]. Many studies determining the susceptibility patterns of clinical strains of Aspergillus spp. are available, but very few have evaluated the susceptibility patterns of environmental strains, especially of * Corresponding author. Tel.: +351 91 603 5076; fax: +351 22 551 0119. E-mail address: ricjparaujo@yahoo.com (R. Araujo). Aspergillus non-fumigatus strains [4–7]. The objective of this study was to determine the susceptibility proﬁles of a large number of environmental strains of six different species of Aspergillus to amphotericin B (AMB), itraconazole (ITC), voriconazole (VRC) and caspofungin (CPF) and to com- pare them with the susceptibility proﬁles of clinical strains. Hypothetical susceptibility differences among environmen- tal Aspergillus spp. might explain native resistance to certain antifungals. 2. Material and methods 2.1. Organisms and isolation sources Four hundred and forty-six Aspergillus strains were stud- ied, comprising A. fumigatus (105 environmental and 66 clinical strains), Aspergillus ﬂavus (59 environmental and 29 clinical strains), Aspergillus niger (46 environmental and 20 clinical strains), Aspergillus terreus (27 environmental 0924-8579/$ – see front matter © 2006 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved. doi:10.1016/j.ijantimicag.2006.09.019