Department of Microbiology, Government Medical College and Hospital, Chandigarh, India.
Department of Microbiology, Government Medical College and Hospital; Department of Parasitology, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
Indian J Med Microbiol. 2020 Jul-Dec;38(3 & 4):390-396. doi: 10.4103/ijmm.IJMM_20_253.
The emergence of carbapenem-resistant Escherichia coli and Klebsiella species is a global threat. We aimed to compare two phenotypic methods and evaluate the genotypic method for the detection of beta-lactamases produced by E. coli and Klebsiella spp.
One hundred and twenty-six E. coli and Klebsiella isolates were examined for phenotypic production of beta-lactamases by using disc diffusion, combined disc test (CDT) and modified carbapenem inactivation method (mCIM). All strains were also studied for the presence of various genes by polymerase chain reaction.
Out of 126 isolates, 96% of the isolates were extended-spectrum β-lactamase (ESBL) producers based on the presence of various ESBL genes. CDT method showed higher number of total (89%) carbapenemases in comparison to mCIM (81%). Among carbapenemases none of the isolates were Klebsiella pneumoniae carbapenemase producer by CDT, while 69% isolates were metallo-beta-lactamase (MBL) producers. Another method, mCIM/ethylene diamine tetraacetic acid mCIM showed 100% agreement for MBL detection. As regards, AmpC and class D carbapenemases; 0.04% and 16% positivity was detected, respectively, based on CDT method. Molecular analysis revealed 91% of the isolates harbouring carbapenemase genes. blawas the most common gene detected followed bybla. Nine of the bla-positive isolates also possessed blagene.
Our finding shows high percentages of ESBL and carbapenemases in E. coli and Klebsiella spp. Among phenotypic methods, CDT seems to be a better choice as prevalence of carbapenemases shows lots of variation in our country. For Class B enzymes, both CDT and mCIM/eCIM can be used in the routine laboratories.
碳青霉烯类耐药的大肠埃希菌和克雷伯菌属的出现是一个全球性的威胁。我们旨在比较两种表型方法，并评估基因方法对大肠埃希菌和克雷伯菌属产β-内酰胺酶的检测。
采用纸片扩散法、联合纸片试验（CDT）和改良碳青霉烯灭活法（mCIM）对 126 株大肠埃希菌和克雷伯菌进行表型产β-内酰胺酶检测，所有菌株均采用聚合酶链反应检测各种基因的存在。
126 株分离株中，89%的分离株存在各种 ESBL 基因，为产超广谱β-内酰胺酶（ESBL）。与 mCIM（81%）相比，CDT 法显示出更多的总（89%）碳青霉烯酶。在碳青霉烯酶中，没有一株分离株为 CDT 型的肺炎克雷伯菌碳青霉烯酶，而 69%的分离株为金属β-内酰胺酶（MBL）。另一种方法，乙二胺四乙酸改良碳青霉烯灭活法（mCIM/EDTA-mCIM）对 MBL 的检测具有 100%的一致性。至于 AmpC 和类 D 碳青霉烯酶，CDT 法检测到的阳性率分别为 0.04%和 16%。分子分析显示 91%的分离株携带碳青霉烯酶基因。blawas 是检测到的最常见基因，其次是 bla。9 株 bla 阳性分离株也携带 blagene。
我们的发现显示大肠埃希菌和克雷伯菌属的 ESBL 和碳青霉烯酶的比例很高。在表型方法中，CDT 似乎是一个更好的选择，因为在我国，碳青霉烯酶的流行率存在很大的差异。对于 B 类酶，CDT 和 mCIM/EDTA-mCIM 都可以在常规实验室中使用。
