Ali Saied, Collison Meadhbh, McNicholas Sinead, McDermott Sinead
Department of Clinical Microbiology, St. Vincent's University Hospital, Elm Park, Dublin 4, Ireland.
Access Microbiol. 2023 Oct 9;5(10). doi: 10.1099/acmi.0.000617.v4. eCollection 2023.
, formerly , is an opportunistic yeast and emerging cause of human infections. The use of broth microdilution (BMD) methodologies for caspofungin (CSP) antifungal susceptibility testing (AFST) against is reported to be prone to high inter-laboratory variation. We aimed to compare CSP MICs of isolates from our institution with those obtained by the Reference Laboratory for the same isolates.
All clinically significant isolates from 2019 to 2021 inclusive were reviewed. AFST was performed locally using the VITEK2 system with the AST-YS08 card, while E-tests were performed at the Mycology Reference Laboratory (MRL), and agreement between these two methods was evaluated - categorical and essential.
Forty-one isolates were reviewed during the study period - 30 from blood cultures, seven from intra-operative theatre specimens and four from sterile site drain fluids. Despite an essential agreement of 100 % within ±2 log dilutions, marked discrepancies were noted in interpretative breakpoints between assays with 17 Minor and 16 Major category errors. Categorical agreement was 19.5 %, with the VITEK2 over-estimating resistance. A Mann-Whitney U-test assessed the relationship of MICs across the AFST modalities, and a statistically significant difference was noted, <0.01, with a higher mean rank for VITKEK2 outputs.
While the VITEK2 system is highly applicable, its performance for CSP AFST is unreliable and potentially results in the mis-classification of susceptible isolates as highlighted in our study. The use of VITEK2 AST-YS08 micafungin as a sentinel echinocandin should be explored and/or the evaluation of CSP-specific E-tests as utilized by the MRL. These methods appear more consistent and less prone to the variation seen with BMD for CSP.
，以前称为 ，是一种机会性酵母，也是人类感染的新兴病因。据报道，使用肉汤微量稀释（BMD）方法进行卡泊芬净（CSP）对 的抗真菌药敏试验（AFST）容易出现较高的实验室间差异。我们旨在比较本机构分离的 菌株的CSP MIC与参考实验室对相同菌株获得的结果。
回顾了2019年至2021年期间所有具有临床意义的 分离株。在本地使用带有AST-YS08卡的VITEK2系统进行AFST，而在真菌学参考实验室（MRL）进行E试验，并评估这两种方法之间的一致性——分类一致性和基本一致性。
在研究期间共回顾了41株分离株——30株来自血培养，7株来自手术室标本，4株来自无菌部位引流液。尽管在±2对数稀释范围内基本一致性为100%，但在分析之间的解释性断点处发现了明显差异，有17个次要类别错误和16个主要类别错误。分类一致性为19.5%，VITEK2高估了耐药性。Mann-Whitney U检验评估了不同AFST模式下MICs的关系，发现有统计学显著差异，<0.01，VITKEK2输出的平均秩更高。
虽然VITEK2系统具有高度适用性，但其在CSP AFST中的表现不可靠，可能导致易感菌株的错误分类，正如我们研究中所强调的。应探索使用VITEK2 AST-YS08米卡芬净作为哨兵棘白菌素，和/或评估MRL使用的CSP特异性E试验。这些方法似乎更一致，不太容易出现CSP的BMD所见的差异。
