Swenson Jana M, Anderson Karen F, Lonsway David R, Thompson Angela, McAllister Sigrid K, Limbago Brandi M, Carey Roberta B, Tenover Fred C, Patel Jean B
Clinical and Environmental Microbiology Branch, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
J Clin Microbiol. 2009 Jul;47(7):2013-7. doi: 10.1128/JCM.00221-09. Epub 2009 May 6.
We compared the results obtained with six commercial MIC test systems (Etest, MicroScan, Phoenix, Sensititre, Vitek Legacy, and Vitek 2 systems) and three reference methods (agar dilution, disk diffusion, and vancomycin [VA] agar screen [VScr]) with the results obtained by the Clinical and Laboratory Standards Institute broth microdilution (BMD) reference method for the detection of VA-intermediate Staphylococcus aureus (VISA). A total of 129 S. aureus isolates (VA MICs by previous BMD tests, <or=1 microg/ml [n = 60 strains], 2 microg/ml [n = 24], 4 microg/ml [n = 36], or 8 microg/ml [n = 9]) were selected from the Centers for Disease Control and Prevention strain collection. The results of BMD with Difco Mueller-Hinton broth were used as the standard for data analysis. Essential agreement (percent +/-1 dilution) ranged from 98 to 100% for all methods except the method with the Vitek Legacy system, for which it was 90.6%. Of the six commercial MIC systems tested, the Sensititre, Vitek Legacy, and Vitek 2 systems tended to categorize VISA strains as susceptible (i.e., they undercalled resistance); the MicroScan and Phoenix systems and Etest tended to categorize susceptible strains as VISA; and the Vitek Legacy system tended to categorize VISA strains as resistant (i.e., it overcalled resistance). Disk diffusion categorized all VISA strains as susceptible. No susceptible strains (MICs <or= 2 microg/ml) grew on the VScr, but all strains for which the VA MICs were 8 microg/ml grew on the VScr. Only 12 (33.3%) strains for which the VA MICs were 4 microg/ml grew on VScr. The differentiation of isolates for which the VA MICs were 2 or 4 microg/ml was difficult for most systems and methods, including the reference methods.
我们将六种商用 MIC 测试系统（Etest、MicroScan、Phoenix、Sensititre、Vitek Legacy 和 Vitek 2 系统）以及三种参考方法（琼脂稀释法、纸片扩散法和万古霉素 [VA] 琼脂筛选 [VScr]）检测万古霉素中介金黄色葡萄球菌（VISA）的结果，与临床和实验室标准协会肉汤微量稀释（BMD）参考方法的检测结果进行了比较。从疾病控制与预防中心的菌株库中选取了总共 129 株金黄色葡萄球菌分离株（先前 BMD 测试的 VA MIC，≤1 μg/ml [n = 60 株]、2 μg/ml [n = 24]、4 μg/ml [n = 36] 或 8 μg/ml [n = 9]）。使用含 Difco Mueller-Hinton 肉汤的 BMD 结果作为数据分析的标准。除 Vitek Legacy 系统外，所有方法的基本一致性（±1 倍稀释百分比）范围为 98%至 100%，Vitek Legacy 系统的基本一致性为 90.6%。在测试的六种商用 MIC 系统中，Sensititre、Vitek Legacy 和 Vitek 2 系统倾向于将 VISA 菌株分类为敏感（即它们低估了耐药性）；MicroScan 和 Phoenix 系统以及 Etest 倾向于将敏感菌株分类为 VISA；Vitek Legacy 系统倾向于将 VISA 菌株分类为耐药（即它高估了耐药性）。纸片扩散法将所有 VISA 菌株分类为敏感。没有敏感菌株（MIC≤2 μg/ml）在 VScr 上生长，但所有 VA MIC 为 8 μg/ml 的菌株在 VScr 上生长。VA MIC 为 4 μg/ml 的菌株中只有 12 株（33.3%）在 VScr 上生长。对于大多数系统和方法，包括参考方法，区分 VA MIC 为 2 或 4 μg/ml 的分离株都很困难。
