Tan Grace L, Peterson Ellena M
Department of Pathology, Medical Microbiology Division, University of California Irvine, Medical Center, 101 The City Drive, Orange, CA 92868, USA.
J Clin Microbiol. 2005 Apr;43(4):1727-31. doi: 10.1128/JCM.43.4.1727-1731.2005.
An evaluation was performed on 95 blood cultures positive for Candida spp. to determine the correlation of direct susceptibility testing of fluconazole versus both standardized disk diffusion and MIC methods. For direct testing, an aliquot taken from BD BACTEC Plus and/or BD BACTEC Lytic/10 bottles (Becton Dickinson [BD], Sparks, MD) positive by gram stain for yeast was subcultured to CHROMagar Candida (BD), and a 25-microg fluconazole disk (BD) was placed on the plate. The area of growth inhibition surrounding the disk was measured at 24 and 48 h. In addition, a subculture of the isolate was tested by a microdilution MIC using YeastOne (TREK Diagnostics Systems Inc., OH) and disk diffusion (NCCLS M44-A) using a standardized inoculum plated onto CHROMagar Candida as well as Mueller-Hinton agar to which 2% glucose and 0.5 microg/ml methylene blue dye was added (MH-GMB). The categorical interpretation derived from the MIC was used as the reference to which the disk diffusion results were compared. There were a total of 41 Candida albicans, 23 Candida glabrata, 20 Candida parapsilosis, 9 Candida tropicalis, and 1 each of Candida krusei and Candida lusitaniae tested. At 24 h there was full agreement among the methods for all C. albicans, C. tropicalis, C. lusitaniae, and C. krusei isolates. For the C. parapsilosis isolates at 24 h there was one very major discrepancy using the direct CHROMagar and one major error with the standardized MH-GMB. The majority of the errors were seen at 24 h with the C. glabrata isolates. Of the 23 C. glabrata isolates at 24 h by direct CHROMagar, there were 10 minor and 1 very major error; by MH-GMB there were 12 minor and 2 very major errors; and by standardized CHROMagar Candida there were 13 minor and 2 major errors. There were no very major errors with C. glabrata when all plates were read at 48 h. At 24 h by the direct and standardized CHROMagar the majority of C. glabrata isolates were more resistant, whereas by MH-GMB they were more susceptible than the reference MIC interpretation. In summary, subculturing yeast directly from blood cultures onto CHROMagar to which a fluconazole disk has been added may provide a presumptive identification at 24 h and, with the exception of C. glabrata, was able to predict the susceptibility to fluconazole with the majority of Candida isolates examined in this evaluation.
对95份念珠菌属血培养阳性样本进行了评估，以确定氟康唑直接药敏试验与标准化纸片扩散法和MIC法之间的相关性。对于直接检测，从经革兰氏染色酵母阳性的BD BACTEC Plus和/或BD BACTEC Lytic/10瓶（Becton Dickinson [BD]，斯帕克斯，马里兰州）中取出一份等分试样，接种到CHROMagar Candida（BD）上，并在平板上放置一个25μg氟康唑纸片（BD）。在24小时和48小时测量纸片周围的生长抑制区域。此外，使用YeastOne（TREK诊断系统公司，俄亥俄州）通过微量稀释法对分离株进行MIC检测，并使用标准化接种物接种到CHROMagar Candida以及添加了2%葡萄糖和0.5μg/ml亚甲蓝染料的Mueller-Hinton琼脂（MH-GMB）上，通过纸片扩散法（NCCLS M44-A）进行检测。将MIC得出的分类解释用作比较纸片扩散结果的参考。共检测了41株白色念珠菌、23株光滑念珠菌、20株近平滑念珠菌、9株热带念珠菌以及各1株克柔念珠菌和葡萄牙念珠菌。在24小时时，所有白色念珠菌、热带念珠菌、葡萄牙念珠菌和克柔念珠菌分离株的检测方法之间完全一致。对于24小时的近平滑念珠菌分离株，使用直接CHROMagar检测时有1个非常重大的差异，使用标准化MH-GMB检测时有1个重大错误。大多数错误出现在24小时的光滑念珠菌分离株检测中。在24小时通过直接CHROMagar检测的23株光滑念珠菌分离株中，有10个小错误和1个非常重大的错误；通过MH-GMB检测时有12个小错误和2个非常重大的错误；通过标准化CHROMagar Candida检测时有13个小错误和2个重大错误。当在48小时读取所有平板时，光滑念珠菌没有非常重大的错误。在24小时时，通过直接和标准化CHROMagar检测，大多数光滑念珠菌分离株更耐药，而通过MH-GMB检测时，它们比参考MIC解释更敏感。总之，将酵母直接从血培养物接种到添加了氟康唑纸片的CHROMagar上，可能在24小时提供初步鉴定，并且除光滑念珠菌外，在本次评估中能够预测大多数念珠菌分离株对氟康唑的敏感性。
