Institute of Microbiology, University of Lausanne and University Hospital Center, Lausanne, Switzerland.
Infectious Diseases Service, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland.
Front Cell Infect Microbiol. 2022 May 4;12:859439. doi: 10.3389/fcimb.2022.859439. eCollection 2022.
The antifungal susceptibility testing (AFST) of yeast pathogen alerts clinicians about the potential emergence of resistance. In this study, we compared two commercial microdilution AFST methods: Sensititre YeastOne read visually (YO) and MICRONAUT-AM read visually (MN) or spectrophotometrically (MNV), interpreted with Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing criteria, respectively.
Overall, 97 strains from 19 yeast species were measured for nine antifungal drugs including a total of 873 observations. First, the minimal inhibitory concentration (MIC) was compared between YO and MNV, and between MNV and MN, either directly or by assigning them to five susceptibility categories. Those categories were based on the number of MIC dilutions around the breakpoint or epidemiological cut-off reference values (ECOFFs or ECVs). Second, YO and MNV methods were evaluated for their ability to detect the elevation of MICs due to mutation in antifungal resistance genes, thanks to pairs or triplets of isogenic strains isolated from a single patient along a treatment previously analyzed for antifungal resistance gene mutations. Reproducibility measurement was evaluated, thanks to three quality control (QC) strains.
YO and MNV direct MIC comparisons obtained a global agreement of 67%. Performing susceptibility category comparisons, only 22% and 49% of the MICs could be assigned to categories using breakpoints and ECOFFs/ECVs, respectively, and 40% could not be assigned due to the lack of criteria in both consortia. The YO and MN susceptibility categories gave accuracies as low as 50%, revealing the difficulty to implement this method of comparison. In contrast, using the antifungal resistance gene sequences as a gold standard, we demonstrated that both methods (YO and MN) were equally able to detect the acquisition of resistance in the strains, even if MN showed a global lower MIC elevation than YO. Finally, no major differences in reproducibility were observed between the three AFST methods.
This study demonstrates the valuable use of both commercial microdilution AFST methods to detect antifungal resistance due to point mutations in antifungal resistance genes. We highlighted the difficulty to conduct conclusive analyses without antifungal gene sequence data as a gold standard. Indeed, MIC comparisons taking into account the consortia criteria of interpretation remain difficult even after the effort of harmonization.
酵母病原体的抗真菌药敏试验（AFST）可提醒临床医生潜在的耐药性出现。在这项研究中，我们比较了两种商业微量稀释 AFST 方法：Sensititre YeastOne 目视读取（YO）和 MICRONAUT-AM 目视读取（MN）或分光光度读取（MNV），分别采用临床和实验室标准协会和欧洲抗菌药物敏感性试验委员会的标准进行解释。
共对来自 19 种酵母属的 97 株菌株进行了 9 种抗真菌药物的检测，共获得 873 个观察结果。首先，直接比较 YO 和 MNV 以及 MNV 和 MN 的最小抑菌浓度（MIC），或者通过将其分配到五个药敏类别来比较。这些类别基于围绕断点或流行病学临界值参考值（ECOFF 或 ECV）的 MIC 稀释倍数。其次，通过来自同一患者的一对或三对同基因菌株，这些菌株在先前分析的抗真菌耐药基因突变治疗中分离出来，评估 YO 和 MNV 方法检测由于抗真菌耐药基因突变导致 MIC 升高的能力。通过三个质量控制（QC）菌株评估重现性测量。
YO 和 MNV 直接 MIC 比较获得了 67%的总体一致性。进行药敏类别比较时，使用断点和 ECOFF/ECV 只能将 22%和 49%的 MIC 分配到类别中，由于两个协会都缺乏标准，因此 40%的 MIC 无法分配。YO 和 MN 的药敏类别准确性低至 50%，表明实施这种比较方法存在困难。相比之下，使用抗真菌耐药基因序列作为金标准，我们证明两种方法（YO 和 MN）都能够检测到菌株中耐药性的获得，尽管 MN 显示的 MIC 升高总体低于 YO。最后，三种 AFST 方法之间的重现性没有观察到明显差异。
本研究表明，这两种商业微量稀释 AFST 方法均能有效检测抗真菌耐药性，原因是抗真菌耐药基因的点突变。我们强调，在没有抗真菌基因序列数据作为金标准的情况下，进行结论性分析存在困难。事实上，即使在协调努力之后，考虑到解释的协会标准，MIC 比较仍然很困难。
