Vol.70 No.4 July 2022

Distributions of the minimum inhibitory concentrations and minimum effective concentrations of antifungal agents against Aspergillus spp. in Hokkaido: comparative study of the performance between a home-made plate and commercial kit for susceptibility testing of yeasts

Yuki Yakuwa¹⁾, Natsuki Narumi¹⁾, Yuki Sato¹⁾, Masachika Saeki¹⁾, Shinya Nirasawa¹⁾, Yoshihiro Fujiya^{2, 3)} and Satoshi Takahashi^{1, 3)}

¹⁾Division of Laboratory Medicine, Sapporo Medical University Hospital, 291 South-1, West-16 Chuo-ku, Sapporo, Hokkaido, Japan
²⁾Infectious Disease Center, Hokkaido Institute of Public Health
³⁾Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine

Abstract

The distributions of the minimum inhibitory concentrations (MICs) and minimum effective concentrations (MECs) of amphotericin B (AMPH-B), itraconazole (ITCZ), voriconazole (VRCZ), and micafungin (MCFG) for 48 clinical isolates of Aspergillus spp. in Hokkaido were determined in accordance with the Clinical and Laboratory Standards Institute (CLSI) guideline. In addition, we also evaluated whether commercially available kits for yeast-like fungus drug susceptibility testing could be used for Aspergillus spp.. The CLSI method adopted with the home-made plate indicated that the MIC₅₀/MIC₉₀ (μg/mL) for A. fumigatus was 1/2 for AMPH-B, 0.5/1 for ITCZ, and 0.5/1 for VRCZ, and that the MEC₅₀/MEC₉₀ (μg/mL) was 0.0078/0.015 for MCFG. The MICs of ITCZ and VRCZ for one isolate of A. fumigatus (3.6%) were ≥16 μg/mL and 2 μg/mL, respectively, and this isolate was classified as a Non-Wild-Type (NWT), with acquired resistance to the two drugs. The two log₂ dilutions among the CLSI method, yeast-like fungus DP testing (DP), and testing using the yeast-like fungus drug susceptibility test kit ASTY (ASTY) based on fungal growth as an indicator were fully matched. Moreover, the isolate classified as a NWT based on the MICs of ITCZ and VRCZ determined by the CLSI method was also classified as a NWT by both DP and ASTY, and the results were consistent. In the comparison of the three different methods, only one isolate was classified as a NWT by DP and as a WT by the CLSI method and ASTY. Thus, DP and ASTY can be useful alternatives to the CLSI method for antifungal susceptibility testing of Aspergillus spp..

Key word

Aspergillus spp., antifungal susceptibility testing, clinical and laboratory standards institute

Received

October 20, 2021

Accepted

May 9, 2022

Jpn. J. Chemother. 70 (4): 351-358, 2022