采用传统方法和分子方法检测金黄色葡萄球菌分离株对甲氧西林和莫匹罗星的耐药性：一项来自耐甲氧西林金黄色葡萄球菌（MRSA）高流行率烧伤病房的描述性研究
Detection of methicillin and mupirocin resistance in Staphylococcus aureus isolates using conventional and molecular methods: a descriptive study from a burns unit with high prevalence of MRSA.
作者信息
Krishnan P U, Miles K, Shetty N
机构信息
Department of Clinical Microbiology, University College London Hospitals and PHLS Collaborating Centre, Grafton Way, III Floor, London W1E 6DB, UK.
出版信息
J Clin Pathol. 2002 Oct;55(10):745-8. doi: 10.1136/jcp.55.10.745.
AIMS
To compare conventional phenotypic methods for the detection of methicillin and mupirocin resistance in Staphylococcus aureus in routine laboratory practice with reference to an established molecular method.
METHODS
This study was conducted on a selection of 65 isolates of methicillin resistant Staphylococcus aureus (MRSA) from a burns unit in India which is endemic for MRSA. The Kirby-Bauer and modified Stokes disc diffusion tests and the Vitek breakpoint minimum inhibitory concentration (MIC) were performed on all isolates using the presence of the mecA gene as the reference standard. Gel based and colorimetric polymerase chain reaction (PCR) assays were evaluated as molecular methods for the diagnosis of MRSA. A commercial latex agglutination test, the Mastalex, was assessed for the detection of penicillin binding protein 2a (PBP2a), the mecA gene product. Conventional disc diffusion and molecular methods were investigated for the detection of mupirocin resistance.
RESULTS
Fifty one of 65 isolates were positive for the mecA gene. All three phenotypic methods showed high sensitivity (> 96.2%), whereas the specificity varied: 50% for Kirby-Bauer, 87.5% for modified Stokes, and 93.3% for Vitek. The colorimetric PCR was less cumbersome than the gel based PCR; there was complete concordance between both systems. The Mastalex kit showed good correlation with PCR. One isolate was found to be mupirocin resistant and harboured the mupA gene.
CONCLUSIONS
The specificity of routine laboratory tests for MRSA detection was variable. mecA gene detection, the "gold standard" to confirm ambiguous results, is difficult to perform in routine diagnostic laboratories. The Mastalex kit for the detection of PBP2a is an alternative that could be used in most laboratories. High level mupirocin resistance can be confirmed with genotypic methods.
目的
在常规实验室操作中，参照既定的分子方法，比较检测金黄色葡萄球菌中耐甲氧西林和耐莫匹罗星的传统表型方法。
方法
本研究选取了来自印度一家烧伤病房的65株耐甲氧西林金黄色葡萄球菌（MRSA）分离株，该病房为MRSA的地方性流行区。以mecA基因的存在作为参考标准，对所有分离株进行了 Kirby-Bauer和改良 Stokes纸片扩散试验以及Vitek断点最低抑菌浓度（MIC）检测。评估了基于凝胶和比色聚合酶链反应（PCR）检测法作为诊断MRSA的分子方法。对一种用于检测青霉素结合蛋白2a（PBP2a，即mecA基因产物）的商业乳胶凝集试验（Mastalex）进行了评估。研究了传统纸片扩散法和分子方法用于检测莫匹罗星耐药性的情况。
结果
65株分离株中有51株mecA基因呈阳性。所有三种表型方法均显示出高灵敏度（>96.2%），而特异性有所不同：Kirby-Bauer法为50%，改良 Stokes法为87.5%，Vitek法为93.3%。比色PCR比基于凝胶的PCR操作更简便；两种系统结果完全一致。Mastalex试剂盒与PCR结果具有良好的相关性。发现一株分离株耐莫匹罗星且携带mupA基因。
结论
常规实验室检测MRSA的特异性存在差异。mecA基因检测作为确认不确定结果的“金标准”，在常规诊断实验室中难以实施。用于检测PBP2a的Mastalex试剂盒是大多数实验室可采用的替代方法。高水平莫匹罗星耐药性可用基因型方法确认。
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