Pfaller M A, Messer S A, Coffmann S
Department of Pathology, University of Iowa College of Medicine, Iowa City 52242, USA.
J Clin Microbiol. 1995 May;33(5):1094-7. doi: 10.1128/jcm.33.5.1094-1097.1995.
A study to compare three different methods for reading MIC endpoints tested by the broth microdilution modification of the National Committee for Clinical Laboratory Standards (Villanova, Pa.) reference method was conducted. MICs of amphotericin B, flucytosine, fluconazole, itraconazole, and a new triazole, D0870, were determined for five reference yeast strains and 100 clinical isolates of Candida spp. MICs were read visually according to National Committee for Clinical Laboratory Standards guidelines from microdilution trays that had been (VS) and had not been (V) shaken. MICs were also determined spectrophotometrically (SP) at 492 nm. SP endpoints were determined as the concentrations resulting in a > or = 50% inhibition of growth (flucytosine and azoles) and a > or = 90% inhibition of growth (amphotericin B) relative to control growth. The five reference strains were tested nine times each against all five antifungal agents, and the MIC results for each reading method were compared with a 3-log2 dilution reference range determined by the macrodilution (M27-P) method. Overall, 84 to 100% of the MICs determined by V, 93 to 100% of those determined by VS, and 89 to 100% of those determined by SP fell within the 3-log2 dilution reference range for each reference strain and antifungal agent. Reproducibility was 99% for V and SP and 98% for VS. Agreement among the three methods of reading ranged from 97 to 99%. Excellent agreement among reading methods was also observed for all antifungal agents when tested against 100 clinical isolates. Agreement between the standard V method (no agitation) and VS ranged from 99 to 100%, and that between V and SP ranged from 89 to 99%. The VS and SP reading methods provided more definitive endpoints than the V method, which does not involve shaking.
开展了一项研究，比较三种不同的读取最低抑菌浓度（MIC）终点的方法，这些方法通过对美国国家临床实验室标准委员会（宾夕法尼亚州维拉诺瓦）参考方法进行肉汤微量稀释改良来进行测试。测定了两性霉素B、氟胞嘧啶、氟康唑、伊曲康唑和一种新型三唑类药物D0870对5种参考酵母菌株和100株念珠菌属临床分离株的MIC。根据美国国家临床实验室标准委员会的指南，通过肉眼读取微量稀释板上的MIC，这些微量稀释板有的经过（VS）摇晃，有的未经过（V）摇晃。还在492nm波长下通过分光光度法（SP）测定MIC。SP终点被确定为相对于对照生长导致生长抑制≥50%（氟胞嘧啶和唑类药物）以及生长抑制≥90%（两性霉素B）的浓度。5种参考菌株针对所有5种抗真菌药物各测试9次，将每种读取方法的MIC结果与通过常量稀释（M27 - P）方法确定的3-log2稀释参考范围进行比较。总体而言，对于每种参考菌株和抗真菌药物，V法测定的MIC中有84%至100%、VS法测定的中有93%至100%、SP法测定的中有89%至100%落在3-log2稀释参考范围内。V法和SP法的重现性为99%，VS法为98%。三种读取方法之间的一致性在97%至99%之间。当针对100株临床分离株进行测试时，对于所有抗真菌药物，读取方法之间也观察到了极好的一致性。标准V法（不搅拌）和VS法之间的一致性在99%至100%之间，V法和SP法之间的一致性在89%至99%之间。VS法和SP法读取终点比不涉及摇晃的V法更明确。
