Arendrup Maiken Cavling, Arikan-Akdagli Sevtap, Castanheira Mariana, Guinea Jesus, Locke Jeffrey B, Meletiadis Joseph, Zaragoza Oscar
Unit of Mycology, Statens Serum Institut, Copenhagen, Denmark.
Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark.
J Antimicrob Chemother. 2022 Dec 23;78(1):185-195. doi: 10.1093/jac/dkac373.
Rezafungin EUCAST MIC testing has been associated with notable inter-laboratory variation, which prevented ECOFF setting for C. albicans. We assessed in vitro susceptibility and reproducibility for a modified EUCAST methodology and established associated wild-type upper limits (WT-ULs).
MICs against 150 clinical Candida isolates (six species), molecularly characterized fks mutants (n = 13), and QC strains (n = 6) were determined at six laboratories according to E.Def 7.3 but using Tween 20 supplemented medium. WT-ULs were determined using the derivatization method, the ECOFFinder programme and visual inspection. Consensus WT-ULs were determined.
The laboratory- and species-specific MIC distributions were Gaussian with >99.5% MICs within four 2-fold dilutions except for C. parapsilosis (92.8%). The following consensus WT-UL were determined: C. albicans 0.008 mg/L; C. dubliniensis and C. glabrata 0.016 mg/L; C. krusei and C. tropicalis 0.03 mg/L; and C. parapsilosis 4 mg/L. Adopting these WT-UL, six clinical isolates were non-wild-type, five of which harboured Fks alterations. For 11/13 mutants, all 670 MICs were categorized as non-wild-type whereas MICs for C. glabrata Fks2 D666Y and C. tropicalis Fks1 R656R/G overlapped with the corresponding wild-type distributions. Repeat testing of six reference strains yielded 98.3%-100% of MICs within three 2-fold dilutions except for C. albicans CNM-CL-F8555 (96%) and C. parapsilosis ATCC 22019 (93.3%).
The modified EUCAST method significantly improved inter-laboratory variation, identified wild-type populations and allowed perfect separation of wild-type and fks mutants except for two isolates harbouring weak mutations. These consensus WT-UL have been accepted as ECOFFs and will be used for rezafungin breakpoint setting.
瑞扎芬净的欧洲抗菌药物敏感性试验委员会（EUCAST）最低抑菌浓度（MIC）检测存在显著的实验室间差异，这阻碍了白色念珠菌的流行病学临界值（ECOFF）设定。我们评估了改良EUCAST方法的体外敏感性和可重复性，并确定了相关的野生型上限（WT-ULs）。
按照E.Def 7.3，但使用添加吐温20的培养基，在六个实验室对150株临床念珠菌分离株（六种菌种）、经分子特征鉴定的fks突变株（n = 13）和质量控制菌株（n = 6）测定MIC。使用衍生化方法、ECOFFinder程序和目视检查确定WT-ULs。确定了共识WT-ULs。
除近平滑念珠菌（92.8%）外，各实验室和菌种特异性的MIC分布呈高斯分布，超过99.5%的MIC在四个2倍稀释度范围内。确定了以下共识WT-UL：白色念珠菌0.008mg/L；都柏林念珠菌和光滑念珠菌0.016mg/L；克鲁斯念珠菌和热带念珠菌0.03mg/L；近平滑念珠菌4mg/L。采用这些WT-UL，六株临床分离株为非野生型，其中五株存在Fks改变。对于11/13个突变株，所有670个MIC均被分类为非野生型，而光滑念珠菌Fks2 D666Y和热带念珠菌Fks1 R656R/G的MIC与相应的野生型分布重叠。除白色念珠菌CNM-CL-F8555（96%）和近平滑念珠菌ATCC 22019（93.3%）外，六种参考菌株的重复检测结果显示，超过98.3%-100%的MIC在三个2倍稀释度范围内。
改良的EUCAST方法显著改善了实验室间差异，确定了野生型群体，并能完美区分野生型和fks突变株，但有两株携带弱突变的分离株除外。这些共识WT-UL已被接受为ECOFFs，并将用于瑞扎芬净折点设定。
