Comparison of the Sensititre YeastOne colorimetric antifungal panel with CLSI microdilution for antifungal susceptibility testing of the echinocandins against Candida spp., using new clinical breakpoints and epidemiological cutoff values.

A commercially prepared dried colorimetric microdilution panel (Sensititre Yeast One, TREK Diagnostic Systems, Cleveland, OH, USA) was compared in 3 different laboratories with the Clinical and Laboratory Standards Institute (CLSI) reference microdilution method by testing 2 quality control strains, 25 reproducibility strains, and 404 isolates of Candida spp. against anidulafungin, caspofungin, and micafungin. Reference CLSI BMD MIC end points and YeastOne colorimetric end points were read after 24 h of incubation. Excellent (100%) essential agreement (within 2 dilutions) between the reference and colorimetric MICs was observed. Categorical agreement (CA) between the 2 methods was assessed using the new species-specific clinical breakpoints (CBPs): susceptible (S), ≤0.25 µg/mL; intermediate (I), 0.5 µg/mL; and resistant (R), ≥1 µg/mL, for C. albicans, C. tropicalis, and C. krusei, and ≤2 µg/mL (S), 4 µg/mL (I), and ≥8 µg/mL (R) for C. parapsilosis and all 3 echinocandins. The new CBPs for anidulafungin and caspofungin and C. glabrata are ≤0.12 µg/mL (S), 0.25 µg/mL (I), and ≥0.5 µg/mL (R), whereas those for micafungin are ≤0.06 µg/mL (S), 0.12 µg/mL (I), and ≥0.25 µg/mL (R). Due to the lack of CBPs for any of the echinocandins and C. lusitaniae, the epidemiological cutoff values (ECVs) were used for this species to categorize the isolates as wild-type (WT; MIC ≤ECV) and non-WT (MIC >ECV), respectively, for anidulafungin (≤2 µg/mL/>2 µg/mL), caspofungin (≤1 µg/mL/>1 µg/mL), and micafungin (≤0.5 µg/mL/>0.5 µg/mL). CA ranged from 93.6% (caspofungin) to 99.6% (micafungin) with less than 1% very major or major errors. The YeastOne colorimetric method remains comparable to the CLSI BMD reference method for testing the susceptibility of Candida spp. to the echinocandins when using the new (lower) CBPs and ECVs. Further study using defined fks mutant strains of Candida is warranted.

Clinical evaluation of the Sensititre YeastOne colorimetric antifungal panel for antifungal susceptibility testing of the echinocandins anidulafungin, caspofungin, and micafungin.

A commercially prepared, dried colorimetric microdilution panel (Sensititre YeastOne Trek Diagnostic Systems, Cleveland, OH) was compared in three different laboratories with the Clinical and Laboratory Standards Institute (CLSI) reference microdilution method by testing 2 quality control strains, 25 reproducibility strains, and 404 isolates of Candida spp. against anidulafungin, caspofungin, and micafungin. Reference MIC endpoints and YeastOne colorimetric endpoints were read after 24 h of incubation. YeastOne endpoints were determined to be the lowest concentration at which the color in the well changed from red (positive, indicating growth) to blue (negative, indicating no growth). Excellent essential agreement (within 2 dilutions) between the reference and colorimetric MICs was observed. Overall agreement was 100% for all three agents. Categorical agreement ranged from 99.3% (anidulafungin) to 100% (caspofungin, micafungin) and interlaboratory reproducibility was 99%. The YeastOne colorimetric method appears to be comparable to the CLSI reference method for testing the susceptibility of Candida spp. to the echinocandins anidulafungin, caspofungin, and micafungin.

Multicenter comparison of the Sensititre YeastOne colorimetric antifungal panel with the NCCLS M27-A2 reference method for testing new antifungal agents against clinical isolates of Candida spp.

A multicenter (three centers) study compared MICs obtained by the Sensititre YeastOne Colorimetric Antifungal plate to reference microdilution broth (NCCLS M27-A2 document) MICs of three new triazoles (posaconazole, ravuconazole, and voriconazole) and the echinocandin caspofungin acetate for 100 isolates of Candida spp. In addition, amphotericin B and fluconazole were tested as control drugs. Colorimetric MICs of caspofungin and amphotericin B corresponded to the first blue well (no growth), and MICs of the other agents corresponded to the first slightly purple or blue well. Two comparisons of MIC pairs by the two methods were evaluated: 24-h colorimetric MICs were compared to NCCLS MICs at 24 and at 48 h. The interlaboratory reproducibility of YeastOne and reference MICs was also examined. The best performance of the YeastOne plate was with 24-h MICs (overall, 95 to 99% agreement) for all the species and antifungal agents. These results suggest the potential value of the YeastOne plate for use in the clinical laboratory for the four new antifungal agents evaluated.

Multisite reproducibility of MIC results by the Sensititre YeastOne colorimetric antifungal susceptibility panel.

Reproducibility of MIC results between laboratories, a major performance criterion used for evaluation of any susceptibility test method, was determined at three test sites using the Sensititre YeastOne Antifungal Panel, which incorporates Alamar Blue as a colorimetric indicator. MICs of five antifungals were determined using a set of 10 isolates of Candida species. Each isolate was tested a total of nine times against each antifungal agent in each of the three laboratories. A total of 1350 MICs were evaluated. MICs were read visually after incubation at 35 degrees C for 24 and 48 h. Overall, 99 to 100% of MIC values were encompassed by a range defined by the modal MIC +/- 1 dilution for each antifungal agent tested at both 24 h and 48 h. Replicate testing of the quality control isolates recommended by the National Committee for Clinical Laboratory Standards demonstrated excellent agreement between results obtained with the Sensititre YeastOne panel and the MIC reference range for each antifungal agent. These studies demonstrated that the Sensititre YeastOne Antifungal Panel may be used to generate MIC values for at least five different antifungal agents with a high degree of intra- and interlaboratory reproducibility.