Susceptibility of Candida species and various moulds to antimycotic drugs: use of epidemiological cutoff values according to EUCAST and CLSI in an 8-year survey

A collection of 2,834 isolates of Candida spp. and 1,079 isolates of Aspergillus spp. and other moulds that were recovered between 2000 and 2007 in Tyrol, Austria, were examined for their susceptibility to antifungal drugs. The susceptibility of Candida spp. to amphotericin B (AMB), caspofungin (CPF), fluconazole (FLC), and voriconazole (VRC) were studied, while filamentous fungi were tested against AMB, CPF, VRC, itraconazole (ITC), and posaconazole (POS). As EUCAST and CLSI are currently revising their breakpoints for several antifungal agents, epidemiological cutoff values (ECVs) of these two guidelines were used to examine trends in susceptibility. For Candida spp. we noted increases in the percentage of non-wild type isolates which were resistant to CPF, FLC, and VRC. Most noticeably, we observed a change in: C. tropicalis (from 0.9-3.8%) and C. parapsilosis (from 4.0-6.0%) relative to CPF; C. parapsilosis (from 0.8-3.4%) and C. glabrata (from 11.0-20%) against FLC; and C. glabrata (from 3.0-12.0%) for VRC. Among the moulds, most Aspergillus spp. isolates were found to be susceptible to VRC, ITC, and POS, while AMB and POS were confirmed to be the most effective agents against zygomycetes. EUCAST and CLSI should continue their efforts to harmonize their methods of antimicrobial susceptibility testing (AST) and to define additional and shareable epidemiological cutoff values and clinical breakpoints.