Antifungal Susceptibility Profiles of Bloodstream Yeast Isolates by Sensititre YeastOne over Nine Years at a Large Italian Teaching Hospital

ABSTRACTSensititre YeastOne (SYO) is an affordable alternative to the Clinical and Laboratory Standards Institute (CLSI) reference method for antifungal susceptibility testing. In this study, the MICs of yeast isolates from 1,214 bloodstream infection episodes, generated by SYO during hospital laboratory activity (January 2005 to December 2013), were reanalyzed using current CLSI clinical breakpoints/epidemiological cutoff values to assign susceptibility (or the wild-type [WT] phenotype) to systemic antifungal agents. Excluding Candida albicans(57.4% of all isolates [n= 1,250]), the most predominant species were Candida parapsilosiscomplex (20.9%), Candida tropicalis(8.2%), Candida glabrata(6.4%), Candida guilliermondii(1.6%), and Candida krusei(1.3%). Among the non-Candidaspecies (1.9%), 7 were Cryptococcus neoformansand 17 were other species, mainly Rhodotorulaspecies. Over 97% of Candidaisolates were susceptible (WT phenotype) to amphotericin B and flucytosine. Rates of susceptibility (WT phenotype) to fluconazole, itraconazole, and voriconazole were 98.7% in C. albicans, 92.3% in the C. parapsilosiscomplex, 96.1% in C. tropicalis, 92.5% in C. glabrata, 100% in C. guilliermondii, and 100% (excluding fluconazole) in C. krusei. The fluconazole-resistant isolates consisted of 6 C. parapsilosiscomplex isolates, 3 C. glabrataisolates, 2 C. albicansisolates, 2 C. tropicalisisolates, and 1 Candidalusitaniaeisolate. Of the non-Candidaisolates, 2 C. neoformansisolates had the non-WT phenotype for susceptibility to fluconazole, whereas Rhodotorulaisolates had elevated azole MICs. Overall, 99.7% to 99.8% of Candidaisolates were susceptible (WT phenotype) to echinocandins, but 3 isolates were nonsusceptible (either intermediate or resistant) to caspofungin (C. albicans, C. guilliermondii, and C. krusei), anidulafungin (C. albicansand C. guilliermondii), and micafungin (C. albicans). However, when the intrinsically resistant non-Candidaisolates were included, the rate of echinocandin nonsusceptibility reached 1.8%. In summary, the SYO method proved to be able to detect yeast species showing antifungal resistance or reduced susceptibility.