Saad Nadia, Munir Tehmina, Ansari Maliha, Gilani Mehreen, Latif Mahwish, Haroon Amira
Department of Microbiology, Army Medical College, Rawalpindi, National University of Sciences and Technology (NUST), H-12, Islamabad, Pakistan.
J Pak Med Assoc. 2016 Jun;66(6):658-61.
To evaluate sensitivity and specificity of disc approximation test compared to three-dimensional extract test as a phenotypic gold standard test for detection of AmpC beta-lactamase producing Escherichia coli and Klebsiella pneumoniae.
The cross-sectional validation study was conducted from November 2014 to April 2015 at Army Medical College, Rawalpindi, Pakistan. Extended spectrum beta lactamases (ESBLs) were isolated from various clinical specimens. Screening for AmpC beta-lactamases was done by using cefoxitin disc (30µg) showing inhibition zone diameter of <18mm. Screen-positive isolates were subjected to disc approximation test (DAT) and three-dimensional extract test(3-DET).SPSS 20 was used for statistical analysis.
A total of 120 ESBL producing Gram negative rods were included in the study. Out of these 120, 82(68.33%) were found to be AmpC beta-lactamase producing on screening with cefoxitin disc. Amongst these 82 isolates, Escherichia coli were identified in 57(69.51%) and Klebsiella pneumoniae in 25 (30.48%). Phenotypic confirmation by disc approximation test (DAT) identified 43(52.43%). AmpC beta-lactamase producing isolates, whereas gold standard 3-DET showed 38(46.34%) of AmpC beta-lactamase producing isolates. Hence, sensitivity of disc approximation test (DAT) was found to be 88%, specificity was 92%, positive predictive value was 92.68%, negative predictive value was 87.80% and diagnostic accuracy was 90.24%.
Implementation of disc approximation test in the laboratories can help in identifying AmpC beta-lactamase harbouring organisms.
将纸片贴靠试验与三维提取试验进行比较，评估纸片贴靠试验作为检测产AmpCβ-内酰胺酶的大肠埃希菌和肺炎克雷伯菌的表型金标准试验的敏感性和特异性。
2014年11月至2015年4月在巴基斯坦拉瓦尔品第的陆军医学院进行横断面验证研究。从各种临床标本中分离出超广谱β-内酰胺酶（ESBLs）。使用头孢西丁纸片（30μg）进行AmpCβ-内酰胺酶筛查，抑菌圈直径<18mm为筛查阳性。对筛查阳性的分离株进行纸片贴靠试验（DAT）和三维提取试验（3-DET）。使用SPSS 20进行统计分析。
本研究共纳入120株产ESBL的革兰阴性杆菌。在这120株中，用头孢西丁纸片筛查发现82株（68.33%）产AmpCβ-内酰胺酶。在这82株分离株中，鉴定出大肠埃希菌57株（69.51%），肺炎克雷伯菌25株（30.48%）。通过纸片贴靠试验（DAT）进行表型确认的产AmpCβ-内酰胺酶分离株有43株（52.43%），而金标准三维提取试验（3-DET）显示产AmpCβ-内酰胺酶分离株有38株（46.34%）。因此，纸片贴靠试验（DAT）的敏感性为88%，特异性为92%，阳性预测值为92.68%，阴性预测值为87.80%，诊断准确性为90.24%。
在实验室开展纸片贴靠试验有助于鉴定携带AmpCβ-内酰胺酶的微生物。
