万古霉素和达托霉素最低抑菌浓度分布及土耳其耐甲氧西林金黄色葡萄球菌血分离株异质性耐药的发生。
Vancomycin and daptomycin minimum inhibitory concentration distribution and occurrence of heteroresistance among methicillin-resistant Staphylococcus aureus blood isolates in Turkey.
机构信息
Department of Medical Microbiology, Hacettepe University Faculty of Medicine, Ankara, Turkey.
出版信息
BMC Infect Dis. 2013 Dec 10;13:583. doi: 10.1186/1471-2334-13-583.
BACKGROUND
The aim of this study was to determine the distribution of vancomycin and daptomycin MICs among methicillin-resistant Staphylococcus aureus (MRSA) blood isolates, the prevalence of heterogeneous vancomycin-intermediate S. aureus (hVISA) and the relationship between hVISA and vancomycin MIC values.
METHODS
A total of 175 MRSA blood isolates were collected from seven university hospitals in Turkey. All isolates were tested for susceptibility to vancomycin and daptomycin by reference broth microdilution (BMD) and by standard Etest method. BMD test was performed according to CLSI guidelines and Etest was performed according to the instructions of the manufacturer. All isolates were screened for the presence of the hVISA by using macro Etest (MET) and population analysis profile-area under the curve (PAP-AUC) methods.
RESULTS
The vancomycin MIC50, MIC90 and MIC ranges were 1, 2, and 0.5-2 μg/ml, respectively, by both of BMD and Etest. The daptomycin MIC50, MIC90 and MIC ranges were 0.5, 1 and 0.125 -1 μg/ml by BMD and 0.25, 0.5 and 0.06-1 μg/ml by Etest, respectively. The vancomycin MIC for 40.6% (71/175) of the MRSA isolates tested was >1 μg/ml by BMD. No vancomycin and daptomycin resistance was found among MRSA isolates. Percent agreement of Etest MICs with BMD MICs within ±1 doubling dilution was 100% and 73.1% for vancomycin and daptomycin, respectively. The prevalence of hVISA among MRSA blood isolates was 13.7% (24/175) by PAP-AUC method. MET identified only 14 of the hVISA strains (sensitivity, 58.3%), and there were 12 strains identified as hVISA that were not subsequently confirmed by PAP-AUC (specificity, 92.1%).
CONCLUSIONS
Agreement between BMD and Etest MICs is high both for vancomycin and daptomycin. Daptomycin was found to be highly active against MRSA isolates including hVISA. A considerable number of isolates are determined as hVISA among blood isolates. As it is impractical to use the reference method (PAP-AUC) for large numbers of isolates, laboratory methods for rapid and accurate identification of hVISA need to be developed.
背景
本研究旨在确定耐甲氧西林金黄色葡萄球菌（MRSA）血分离株中万古霉素和达托霉素 MIC 的分布、表型万古霉素中介金黄色葡萄球菌（hVISA）的流行情况以及 hVISA 与万古霉素 MIC 值之间的关系。
方法
从土耳其的 7 家大学医院收集了 175 株 MRSA 血分离株。所有分离株均通过参考肉汤微量稀释法（BMD）和标准 Etest 法检测对万古霉素和达托霉素的敏感性。BMD 试验按照 CLSI 指南进行，Etest 按照制造商的说明进行。所有分离株均通过大 Etest（MET）和群体分析曲线下面积（PAP-AUC）方法筛选 hVISA 的存在。
结果
BMD 和 Etest 法检测万古霉素 MIC50、MIC90 和 MIC 范围分别为 1、2 和 0.5-2μg/ml。BMD 法检测达托霉素 MIC50、MIC90 和 MIC 范围分别为 0.5、1 和 0.125-1μg/ml，Etest 法检测分别为 0.25、0.5 和 0.06-1μg/ml。BMD 法检测 40.6%（71/175）MRSA 分离株的万古霉素 MIC ＞1μg/ml。MRSA 分离株中未发现万古霉素和达托霉素耐药。Etest MIC 与 BMD MIC 在±1 倍稀释度内的一致性为 100%和 73.1%，分别为万古霉素和达托霉素。PAP-AUC 法检测到 MRSA 血分离株中 hVISA 的流行率为 13.7%（24/175）。MET 仅鉴定出 14 株 hVISA 株（敏感性，58.3%），而通过 PAP-AUC 鉴定出 12 株被鉴定为 hVISA 的株未被随后证实（特异性，92.1%）。
结论
BMD 和 Etest MIC 之间的一致性对万古霉素和达托霉素均很高。达托霉素对包括 hVISA 在内的 MRSA 分离株具有高度活性。在血分离株中，相当数量的分离株被确定为 hVISA。由于对大量分离株使用参考方法（PAP-AUC）不切实际，因此需要开发用于快速准确鉴定 hVISA 的实验室方法。
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