Comparison of the Sensititre YeastOne Colorimetric Antifungal Panel with a Modified NCCLS M38-A Method To Determine the Activity of Voriconazole against Clinical Isolates of Aspergillus spp

Abstract

The susceptibilities of 63 isolates of Aspergillus spp. to voriconazole were evaluated by a modified NCCLS M38-A method and the Sensititre YeastOne method. The overall agreement was 82.5%, ranging from 100% for Aspergillus niger and Aspergillus terreus to 62.5% for Aspergillus flavus. Discrepancies between the methods were due to higher Sensititre MICs. The Sensititre YeastOne method could have potential value for susceptibility testing of Aspergillus spp. to voriconazole.Over the past decades, the incidence of invasive fungal infections has increased, especially those caused by Aspergillus species (18). The treatment of choice for infected patients remains amphotericin B, although alternative drugs with activities against Aspergillus species are becoming available for clinical use, including antifungal azoles and echinocandins (6,18). Because the number of serious infections caused by Aspergillus spp. has increased, as has the resistance of Aspergillus spp. to established agents, determination of the in vitro susceptibilities of Aspergillus isolates to both established and investigational agents is necessary (6).There is a great need for an easier and reproducible method for in vitro susceptibility testing of filamentous fungi as a guide to selecting and monitoring antifungal therapy. Alternatives to the NCCLS method are currently under investigation, including two commercial methods, E-test and Sensititre YeastOne, which have been evaluated for yeast and molds (1,3,5,6,9,10,11,(13)(14)(15)(16)(17).Our study represents an evaluation of the suitability of Sensititre YeastOne for determining the susceptibilities of Aspergillus spp. isolates to voriconazole. This test is a commercial colorimetric panel that consists of a disposable tray which contains dried serial dilutions of five antifungal agents in individual wells. The wells also contain an oxidation-reduction indicator (Alamar Blue) to generate clear-cut endpoints based on a visually detectable color change. MICs obtained by this method were compared to those obtained by the modified reference broth microdilution method (14).A total of 63 clinical Aspergillus isolates, comprising 24 Aspergillus fumigatus isolates, 16 Aspergillus flavus isolates, 9 Aspergillus terreus isolates, 8 Aspergillus niger isolates, 4 Aspergillus glaucus isolates, and 2 Aspergillus nidulans isolates, were included in this study. These isolates were recovered from clinical specimens of patients at the Valme University Hospital, Seville, Spain, and the Division of Infectious Diseases, Medical College of Virginia, Virginia Commonwealth University, Richmond.Culture, identification, and preservation of strains were done by using routine mycological methods (4, 7). Candida krusei ATCC 6258 and Candida parapsilosis ATCC 22019 were used as quality control strains for susceptibility testing procedures, and Aspergillus fumigatus ATCC 204305 and Aspergillus flavus ATCC 204304 were used as reference strains.The broth microdilution method was performed according to modified NCCLS standard M38-A gu...

Comparison of Three Commercial Assays and a Modified Disk Diffusion Assay with Two Broth Microdilution Reference Assays for Testing Zygomycetes, Aspergillus spp., Candida spp., and Cryptococcus neoformans with Posaconazole and Amphotericin B

“…An 85 to 98% agreement has been demonstrated between reference and YeastOne voriconazole MICs for Aspergillus spp. at 48 h (1,16). Amphotericin B YeastOne MICs were also more in agreement with reference results at 48 h, but the differences were smaller (90 to 100% versus 88 to 100% at 24 h), which indicates that results could be obtained when sufficient growth allows it.…”

“…Both commercial methods have been favorably evaluated for MIC determination of voriconazole, amphotericin B, and itraconazole against Aspergillus spp. and other molds (1,10,20,21,26). More recently, Etest and disk methodology have been applied as alternative methods for testing posaconazole against yeasts (23) and molds (14,17).…”

Comparative Evaluation of Sensititre YeastOne and CLSI M38-A2 Reference Method for Antifungal Susceptibility Testing of Aspergillus spp. against Echinocandins

“…to echinocandins. Comparisons of both methods with other antifungal agents against the most commonly isolated Aspergillus spp., i.e., A. fumigatus, A. flavus, and A. terreus, have yielded agreement rates of 32 to 100% for amphotericin B (7,8,11,12), 78 to 98% for itraconazole (7,11,12), 96 to 100% for posaconazole (6,8), and 62 to 99% for voriconazole (7,9,10 Echinocandin MECs obtained in the present study using the reference CLSI BMD method were comparable to values recorded in previous surveys (13,14). To date, the only available public accessible data concerning the use of Sensititre panel in susceptibility testing of echinocandins against Aspergillus spp.…”

“…There are fewer studies for molds, demonstrating high levels of agreement with the reference methodology for amphotericin B and azoles with Aspergillus spp. (6)(7)(8)(9)(10)(11)(12), while limited data exist for echinocandins. Since Sensititre YeastOne is widely used in routine microbiology laboratories, the aim of the present study was to assess its performance for in vitro susceptibility testing of echinocandins against the three most commonly isolated Aspergillus spp.-A.…”

In Vitro Susceptibility Testing of Aspergillus and Non-Aspergillus Filamentous Moulds to Antifungal Agents: Evaluation of Three Different Methods

“…SYO is a commercial colorimetric panel, that consists of a disposable tray which contains dried serial dilutions of seven antifungal agents in individual wells, which also contain an oxidation-reduction indicator (AlamarBlue) to generate clear-cut endpoints based on a visually detectable change in colour from blue to pink, and this indicates the antifungal activity, reducing the problems caused by the trailing effect in the visual endpoints [11,14,16]. The agar-based E-test method (AB Biomerieux, France) is a commercially available, pre-formed, pre-defined and stable antibiotic method, which uses a plastic test strip impregnated with a continuous concentration gradient of an antifungal agent to determine the minimum inhibitory concentration (MIC) necessary for inhibition of fungal growth [15][16][17].…”