Abstract
Susceptibility testing is an important tool in the clinical setting; its utility is based on the availability of categorical endpoints, breakpoints (BPs) or epidemiological cutoff values (ECVs/ECOFFs). CLSI and EUCAST have developed antifungal susceptibility testing, BPs and ECVs for some fungal species. Although the Concentration Gradient Strip BioMerieux Etest is useful for routine testing in the clinical laboratory, ECVs are not available for all agent/species; the lack of clinical data precludes development of BPs. We re-evaluated and consolidated Etest data points from three previous studies, and included new data. We defined ECOFFinder Etest ECVs for three sets of species/agent combinations: fluconazole, posaconazole and voriconazole and 8 Candida spp.; amphotericin B and 3 non-prevalent Candida spp.; and caspofungin and 5 Aspergillus spp. The total of Etest MICs from 23 laboratories (Europe, the Americas, South Africa) included (antifungal agent/dependent): 17,242 Candida albicans, 244 C. dubliniensis, 5,129 C. glabrata species complex (SC), 275 C. guilliermondii (Meyerozyma guilliermondii), 1,133 C. krusei (Pichia kudriavzevii), 933 C. kefyr (Kluyveromyces marxianus), 519 C. lusitaniae (Clavispora lusitaniae), 2,947 C. parapsilosis SC, 2,214 C. tropicalis, 3,212 Aspergillus fumigatus, 232 A. flavus, 181 A. niger, and 267 A. terreus SC isolates. Triazole MICs for 66 confirmed non-wild-type (non-WT) Candida isolates were available (ERG11 point mutations). Distributions fulfilling CLSI ECV criteria were pooled and ECOFFinder Etest ECVs were established for triazoles (9 Candida spp.); amphotericin B (3 less-prevalent Candida spp.) and caspofungin (4 Aspergillus spp.). Etest fluconazole ECVs could be good detectors of Candida non-WT isolates (59/61 Non-WT: 4 of 6 species).