微量法检测念珠菌对三唑类药物敏感性与交叉耐药性

Evaluation of broth microdilution antifungal susceptibility testing of Candida spp. against triazole by reference method of NCCLS

目的应用美国临床实验室标准化委员会（ＮＣＣＬＳ）推荐微量法测定酵母菌最低抑菌浓度（ＭＩＣ），并检验其重复性和准确性，观察氟康唑耐药株对伊曲康唑是否存在交叉耐药性。方法参照ＮＣＣＬＳ推荐的药敏试验方案微量稀释法（１９９５年版），检测２５株氟康唑耐药性白念珠菌及４８株临床分离株对氟康唑及伊曲康唑的敏感性。结果２５株氟康唑耐药白念珠菌中只有３株菌对伊曲康唑耐药（ＭＩＣ值≥４μｇ／ｍｌ），占１３．０４％，只有少数菌对伊曲康唑存在交叉耐药。４８株临床分离白念珠菌对氟康唑和伊曲康唑的ＭＩＣ值呈正态分布，有４６株对伊曲康唑的ＭＩＣ值介于０．００７５～４μｇ／ｍｌ，其半数抑菌浓度（ＩＣ５０）为０．１２５μｇ／ｍｌ，有４３株对氟康唑的ＭＩＣ值介于０．２５～１６μｇ／ｍｌ，其ＩＣ５０为２μｇ／ｍｌ。结论ＮＣＣＬＳ微量稀释法有较好的可重复性和稳定性，少数氟康唑耐药株对伊曲康唑有交叉耐药性。

Objective To estabilish the NCCLS microdilution antifungal susceptibility testing of yeast and to evaluatei its reproducibility and whether the isolates resistant to fluconazole are cross resistant to itraconazole or not.Methods The minimum inhibitory concentrations (MICs) of fluconazole and itraconazole were determined by broth microdilution method according to the National Committee on Clinical Laboratory Standards (NCCLS) reference method for broth dilution antifungal susceptibility testing of yeast.Results Of the 25 isolates resistant to fluconazole, 3 (13.03%) Candida albicans were cross resistant to itraconazole. Most clinical isolates of Canadida albicans were susceptible to fluconazole and itraconazole. 46 of the 48 isolates were susceptible to itraconazole (MIC between 0.0075 ～4 μg/ml), and 43 were susceptible to fluconazole (MIC between 0.25～16 μg/ml). The itraconazole IC 50 ( 0.125 μg/ml) for C.albicans of clinical isolates were lower than those (0.5 μg/ml) for resistant isolates.Conclusion The data indicated that the mirodilution method, performed according to NCCLS guidelines, is reproducible and standardized and that the microdilution method is of clinical utility in laboratories in antifungal susceptibility testing of yeast.