Practical Approach for Reliable Detection of AmpC Beta-Lactamase-Producing Enterobacteriaceae
Practical Approach for Reliable Detection of AmpC Beta-Lactamase-Producing Enterobacteriaceae
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DOI：
10.1128/jcm.00404-11
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发表时间：
2011-08-01
影响因子：
9.4
通讯作者：
Hombach, Michael
中科院分区：
文献类型：
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作者：
Polsfuss, Silke;Bloemberg, Guido V.;Hombach, Michael
在这项前瞻性研究中，对2009年10月至2010年4月在临床微生物学实验室发现的所有肠杆菌科分离株(n-2,129)进行了AmpC酶的分析。临床和实验室标准研究所(CLSI)的头孢西丁和头孢替坦的敏感点和CLSI的临界ESBL直径被用来筛选潜在的AmpC菌株。总共有305株细菌(211株潜在的AmpC酶产生菌和94株阴性的AmpC酶菌株作为对照组)进行了多重聚合酶链式反应和AmpC酶启动子序列分析(以金标准)。头孢西丁和头孢替坦被评估为主要筛查标志物。头孢西丁和头孢替坦检测AmpC酶的敏感性分别为97.4%和52.6%，特异性分别为78.7%和99.3%。作为表型确认试验，比较了Etest AmpC法和头孢西丁-氯唑西林双纸片协同法(CC-DDS)。Etest-AMPC法和CC-DDS法的敏感性分别为77.4%和97.2%，特异性均为100%。10个菌株的Etest AmpC检测结果不确定。CC-DDS法观察到2个不确定的结果。基于这项研究，我们提出了一种检测AmpC酶产生的综合诊断流程图，包括简单的表型筛选和单一的表型确认试验，不确定的结果将通过分子分析来解决。在(I)头孢西丁作为AmpC产生的筛选标记，(Ii)CC-DDS方法作为表型确认，(Iii)在结果不确定的情况下，对于所研究的菌株，AmpC检测的敏感性和特异性分别为97.4%和100%。AMPC算法中使用的表型方法操作简单，易于在诊断实验室中实现。
In this prospective study all Enterobacteriaceae isolates (n - 2,129) recovered in the clinical microbiology laboratory during October 2009 to April 2010 were analyzed for AmpC production. Clinical and Laboratory Standards Institute (CLSI) cefoxitin and cefotetan susceptibility breakpoints and CLSI critical ESBL diameters were used to screen for potential AmpC producers. In total, 305 isolates (211 potential AmpC producers and 94 AmpC screen-negative isolates as a control group) were further analyzed by multiplex PCR for the detection of plasmid-encoded ampC beta-lactamase genes and by ampC promoter sequence analysis (considered as the gold standard). Cefoxitin and cefotetan were assessed as primary screening markers. The sensitivities of cefoxitin and cefotetan for the detection of AmpC production were 97.4 and 52.6%, respectively, and the specificities were 78.7 and 99.3%, respectively. As a phenotypic confirmation test, the Etest AmpC and the cefoxitin-cloxacillin double-disk synergy method (CC-DDS) were compared. The sensitivities for the Etest AmpC and the CC-DDS method were 77.4 and 97.2%, respectively, and the specificity was 100% for both methods. The results of the Etest AmpC were inconclusive for 10 isolates. With the CC-DDS method 2 inconclusive results were observed. Based on this study, we propose a comprehensive diagnostic flow chart for the detection of AmpC production consisting of a simple phenotypic screening and a single phenotypic confirmation test with inconclusive results being resolved by molecular analysis. For the proposed flow chart using (i) cefoxitin as a screening marker for AmpC production, (ii) the CC-DDS method as phenotypic confirmation, and (iii) molecular methods in case of inconclusive results, the sensitivity and specificity for AmpC detection would have been 97.4 and 100%, respectively, with respect to the studied isolates. The phenotypic methods used in the AmpC algorithm are simple to perform and easy to implement in the diagnostic laboratory.