Alonso-Echanove J, Robles B, Jarvis W R
Hospital Infections Program, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
J Clin Microbiol. 1999 Jul;37(7):2148-52. doi: 10.1128/JCM.37.7.2148-2152.1999.
Studies in a variety of U.S. clinical laboratories have demonstrated difficulty in detecting intermediate and low-level vancomycin-resistant enterococci (VRE). The misclassification of "at least intermediate resistant isolates" as vancomycin susceptible may have both clinical implications and a negative impact on measures to control the spread of VRE. No published study has assessed the ability of clinical laboratories in Europe to detect VRE. So, the apparent low prevalence of VRE in European hospitals may be, in part, secondary to the inability of these laboratories to detect all VRE. In an effort to assess European laboratories' proficiency in detecting VRE, we identified 22 laboratories in Spain and asked them to test four VRE strains and one susceptible enterococcal strain from the Centers for Disease Control and Prevention collection. Each organism was tested by the routine antimicrobial susceptibility testing method used by each laboratory. Overall, VRE were correctly identified in 61 of 88 (69.1%) instances. The accuracy of VRE detection varied with the level of resistance and the antimicrobial susceptibility method. The high-level-resistant strain (Enterococcus faecium; MIC, 512 microg/ml) was accurately detected in 20 of 22 (91. 3%) instances, whereas the intermediate-resistant isolate (Enterococcus gallinarum; MIC, 8 microg/ml) was accurately detected in only 11 of 22 (50%) instances. Classification errors occurred in 27 of 88 (30.9%) instances. Misclassification as vancomycin susceptible was the most common error (16 of 27 [59.3%] instances). Our study shows that the participating Spanish laboratories had an overall acceptable proficiency in detecting VRE but that a substantial proportion of VRE isolates with low or intermediate levels of resistance were not detected. We recommend that studies be conducted to validate laboratory proficiency testing as an important step in the prevention and control of the spread of antimicrobial resistance.
美国各类临床实验室的研究表明，检测中度和低度耐万古霉素肠球菌（VRE）存在困难。将“至少中度耐药菌株”误分类为万古霉素敏感菌可能会产生临床影响，并对控制VRE传播的措施产生负面影响。尚无已发表的研究评估欧洲临床实验室检测VRE的能力。因此，欧洲医院中VRE明显较低的流行率可能部分是由于这些实验室无法检测出所有的VRE。为了评估欧洲实验室检测VRE的能力，我们在西班牙确定了22家实验室，并要求它们检测来自疾病控制与预防中心样本库的4株VRE菌株和1株敏感肠球菌菌株。每个实验室都使用各自常规的抗菌药物敏感性检测方法对每种菌株进行检测。总体而言，88例样本中有61例（69.1%）正确鉴定出了VRE。VRE检测的准确性因耐药水平和抗菌药物敏感性检测方法而异。22例样本中有20例（91.3%）准确检测出了高水平耐药菌株（粪肠球菌；MIC，512微克/毫升），而22例样本中只有11例（50%）准确检测出了中度耐药菌株（鹑鸡肠球菌；MIC，8微克/毫升）。88例样本中有27例（30.9%）出现分类错误。最常见的错误是误分类为万古霉素敏感菌（27例中有16例[59.3%]）。我们的研究表明，参与研究的西班牙实验室在检测VRE方面总体上具有可接受的水平，但相当一部分低水平或中等水平耐药的VRE菌株未被检测出来。我们建议开展研究以验证实验室能力验证检测，将其作为预防和控制抗菌药物耐药性传播的重要一步。
