Zou Ming-Xiang, Wu Jing-Min, Li Jun, Dou Qing-Ya, Zhou Rong-Rong, Huang Yuan, Liu Wen-En
Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha 410008, China.
Zhongguo Dang Dai Er Ke Za Zhi. 2012 Aug;14(8):616-21.
To investigate the characteristics of New Delhi metallo-beta-lactamase-1 (NDM-1) gene of Klebsiella pneumoniae (K. pneumoniae) emerging in Hunan, and its relationship to antibiotic resistance.
The clinical strain was isolated from a sputum sample of a child with severe pnemonia and toxic myocarditis who was admitted into a general hospital of Hunan Province. VITEK-2 compact instrument was used for bacterial identification and antibiotic susceptibility test. Modified Hodge test was used for the screening of carbapenemase. EDTA-synergy test and combination disk diffusion test were used for detection of metallo-β-lactamase (MBL). PCR was performed for amplification of NDM-1 genes and the positive products were sequenced and analyzed with BLAST. Conjugation was also performed to analyze mechanisms of antibiotic resistance. The results of antibiotic susceptibility tests were compared before and after conjugation.
The isolated strain was identified as K.pneumoniae. Modified Hodge test, EDTA-synergy test and combination disk diffusion test were all positive for the strain. The homology between gene sequence of PCR amplification products and NDM-1 gene FN396876.1 in the GenBank was 100%. Transconjugant DNA was used as template for the amplification of NDM-1 gene. The amplification products were sequenced and found to be the same as the NDM-1 gene amplification product of the donor strain. The MIC of transconjugant E.coli J53 (NDM-1) to all the β-lactams increased significantly compared with the recipient strain E.coli J53. The MIC of ertapenem and imipenem increased by more than 8 times, while the MIC of ceftazidime and ceftriaxone increased by more than 64 times.
This study first identified a strain of K. pneumoniae carrying NDM-1 in mainland China. NDM-1 gene can be transmitted among different strains and causes extensively drug-resistance to β-lactams.
研究湖南省出现的肺炎克雷伯菌新德里金属β-内酰胺酶-1（NDM-1）基因的特征及其与抗生素耐药性的关系。
临床菌株分离自湖南省某综合医院收治的一名患有重症肺炎和中毒性心肌炎儿童的痰液样本。采用VITEK-2 compact仪器进行细菌鉴定和抗生素敏感性试验。改良Hodge试验用于碳青霉烯酶的筛选。EDTA协同试验和联合纸片扩散试验用于检测金属β-内酰胺酶（MBL）。进行PCR扩增NDM-1基因，对阳性产物进行测序并用BLAST分析。还进行接合试验以分析抗生素耐药机制。比较接合前后抗生素敏感性试验结果。
分离菌株鉴定为肺炎克雷伯菌。改良Hodge试验、EDTA协同试验和联合纸片扩散试验该菌株均为阳性。PCR扩增产物基因序列与GenBank中NDM-1基因FN396876.1的同源性为100%。以转接合子DNA为模板扩增NDM-1基因。扩增产物测序后发现与供体菌株的NDM-1基因扩增产物相同。转接合子大肠杆菌J53（NDM-1）对所有β-内酰胺类抗生素的MIC与受体菌株大肠杆菌J53相比显著增加。厄他培南和美罗培南的MIC增加了8倍以上，而头孢他啶和头孢曲松的MIC增加了64倍以上。
本研究首次在中国大陆鉴定出一株携带NDM-1的肺炎克雷伯菌。NDM-1基因可在不同菌株间传播并导致对β-内酰胺类抗生素广泛耐药。
