Warnock D W, Johnson E M, Rogers T R
PHLS Mycology Reference Laboratory, Public Health Laboratory, Bristol, UK.
J Antimicrob Chemother. 1998 Sep;42(3):321-31. doi: 10.1093/jac/42.3.321.
Ten laboratories tested 18 isolates of Candida spp. and two of Cryptococcus neoformans against amphotericin B, flucytosine, fluconazole and itraconazole on two occasions by the Etest method. Two individuals read each set of results. Of the 18 isolates of Candida spp., five were duplicated, but the participants were not told this. In 40 of the 60 drug-organism combinations studied, at least 80% of the Etest MICs fell within a five-concentration range corresponding to the modal MIC +/- 1 log2 dilution. In five combinations, >50% of the Etest MICs fell outside this five-concentration range. In 17 (85%) of the 20 drug-organism combinations tested in duplicate, at least 80% of the paired Etest results fell within two concentrations of each other (corresponding to one log2 dilution). Overall, 88.5% of the paired Etest results for amphotericin B agreed to within two concentrations, as did 94% of results for flucytosine, 92% for fluconazole and 79% for itraconazole. The broth microdilution MICs of the four antifungal agents for the 15 isolates were measured on five occasions in the Mycology Reference Laboratory, Bristol. In each case, the results fell within a three log2 concentration range. In 24 (40%) of the 60 drug-organism combinations tested, at least 80% of the Etest results fell within the broth microdilution test MIC range, but 27 (45%) showed <50% exact agreement. In 33 (73%) of 45 drug-organism combinations involving flucytosine, fluconazole or itraconazole, at least 80% of the Etest results fell within the same class (susceptible, resistant, or susceptible dependent upon dose) as the broth microdilution results. With fluconazole, the Etest method misclassified three susceptible isolates of Candida spp. as resistant in 1.5-15% of tests. With itraconazole, the Etest misclassified seven susceptible isolates of Candida spp. as resistant in 5-62.5% of tests. The Etest also misclassified both C. neoformans isolates as resistant to flucytosine, fluconazole and itraconazole in 7.5-65% of tests. Our results suggest that the Etest is suitable for routine use with Candida spp. and amphotericin B or flucytosine. It is less reliable for the azoles, and isolates that appear to demonstrate acquired resistance should be retested with well-established reference methods.
十个实验室使用Etest方法，分两次对18株念珠菌属菌株和2株新型隐球菌进行了针对两性霉素B、氟胞嘧啶、氟康唑和伊曲康唑的测试。每组结果由两人读取。在18株念珠菌属菌株中，有5株是重复的，但未告知参与者。在所研究的60种药物-微生物组合中，40种组合中至少80%的Etest最低抑菌浓度（MIC）落在对应于众数MIC±log2稀释度的五个浓度范围内。在五种组合中，超过50%的Etest MIC落在这个五个浓度范围之外。在20种进行重复测试的药物-微生物组合中，17种（85%）的配对Etest结果至少80%落在彼此相差两个浓度（对应于一个log2稀释度）的范围内。总体而言，两性霉素B的配对Etest结果88.5%在相差两个浓度范围内相符，氟胞嘧啶为94%，氟康唑为92%，伊曲康唑为79%。在布里斯托尔的真菌学参考实验室，对15株菌株的四种抗真菌药物的肉汤微量稀释MIC进行了五次测量。每种情况下，结果都落在三个log2浓度范围内。在测试的60种药物-微生物组合中，24种（40%）组合中至少80%的Etest结果落在肉汤微量稀释测试MIC范围内，但27种（45%）显示精确相符率低于50%。在涉及氟胞嘧啶、氟康唑或伊曲康唑的45种药物-微生物组合中，33种（73%）组合中至少80%的Etest结果与肉汤微量稀释结果属于同一类别（敏感、耐药或剂量依赖性敏感）。对于氟康唑，Etest方法在1.5% - 15%的测试中将三株敏感的念珠菌属菌株误分类为耐药。对于伊曲康唑，Etest方法在5% - 62.5%的测试中将七株敏感的念珠菌属菌株误分类为耐药。Etest方法还在7.5% - 65%的测试中将两株新型隐球菌菌株误分类为对氟胞嘧啶、氟康唑和伊曲康唑耐药。我们的结果表明，Etest适用于念珠菌属菌株以及两性霉素B或氟胞嘧啶的常规检测。对于唑类药物，其可靠性较低，对于表现出获得性耐药的菌株，应使用成熟的参考方法重新检测。
