Atcc 6258

Eighteen clinical isolates of C. krusei from hospitalized patients (12 urine, four blood, one catheter tip and one bronchoalveolar lavage) and the reference strain C. krusei ATCC 6258 (American Type Culture Collection) were used. They belong to the archive collection of the Medical Mycology Laboratory of the State University of Maringá, Paraná, Brazil (Human Research Ethics Committee COPEP no. 2.748.843). Except for the minimal inhibitory concentration determination and the checkerboard assay, all experiments were performed with the reference strain of C. krusei only.
In each experiment, the yeast was subcultured on Sabouraud dextrose agar (SDA, Difco^tm, Detroit, MI, USA) at 35°C for 24 hours. The cellular density was adjusted using a Neubauer chamber before each assay.

Candida spp. were isolated from blood using BD BACTEC™ FX (Becton, Dickinson and Company, Sparks, MD). The species were identified using MALDI Biotyper (BrukerDaltonik GmbH, Germany), morphology studies on cornmeal Tween 80 agar, and API 20C AUX (Biomerieux, Marcy l’Etoile, France). Isolates were stored in Microbank^TM storage vials (Pro-Lab Diagnostics, Round Rock, TX, USA) at −70 °C until testing.
Antifungal susceptibility testing was performed using Sensititre YeastOne® YO10 panel (Trek Diagnostics System, West Sussex, England) according to manufacturer’s recommendations. Minimum inhibitory concentrations (MICs) for amphotericin B, anidulafungin, caspofungin, micafungin, fluconazole, voriconazole, itraconazole, posaconazole and flucytosine were recorded. Candida krusei (Issatchenkia orientalis) ATCC 6258 and C. parapsilosis ATCC 22019 (American Type Culture Collection, Manassas, Virginia) were used as quality controls.
MICs were interpreted according to the current species-specific clinical breakpoints provided by the Clinical and Laboratory Standards Institute (CLSI) M27-S4 document [12 ]. Where clinical breakpoints were not available, the epidemiological cut-off values (ECV) were used to classify the isolates into wild-type or non-wild-type populations [13 (link)–15 (link)].