Abstract：OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
［1］Nordmann P, Naas T, Poirel L. Global spread of Carbapenemase-producing Enterobacteriaceae［J］. Emerg Infect Dis, 2011, 17(10): 1791-1798.
［2］Cheng X, Wang P, Wang Y, Zhang H, Tao C, Yang W, et al. Identification and distribution of the clinical isolates of imipenem-resistant Pseudomonas aeruginosa carrying metallo-beta-lactamase and/or class 1 integron genes［J］. J Huazhong Univ Sci Technolog Med Sci, 2008, 28(3): 235-238.
［3］Yong D, Toleman MA, Giske CG, Cho HS, Sundman K, Lee K, et al. Characterization of a new metallo-beta-lactamase gene, bla(NDM-1), and a novel erythromycin esterase gene carried on a unique genetic structure in Klebsiella pneumoniae sequence type 14 from India［J］. Antimicrob Agents Chemother, 2009, 53(12): 5046-5054.
［4］Kumarasamy KK, Toleman MA, Walsh TR, Bagaria J, Butt F, Balakrishnan R, et al. Emergence of a new antibiotic resistance mechanism in India, Pakistan, and the UK: a molecular, biological, and epidemiological study［J］. Lancet Infect Dis, 2010,10(9): 597-602.
［5］Nordmann P, Poirel L, Toleman MA, Walsh TR. Does broad-spectrum beta-lactam resistance due to NDM-1 herald the end of the antibiotic era for treatment of infections caused by Gram-negative bacteria?［J］. J Antimicrob Chemother, 2011, 66(4): 689-692.
［6］Ho PL, Lo WU, Yeung MK, Lin CH, Chow KH, Ang I, et al. Complete sequencing of pNDM-HK encoding NDM-1 carbapenemase from a multidrug-resistant Escherichia coli strain isolated in Hong Kong［J］. PLoS One, 2011, 6(3): e17989.
［7］Wu HS, Chen TL, Chen IC, Huang MS, Wang FD, Fung CP, et al. First identification of a patient colonized with Klebsiella pneumoniae carrying blaNDM1 in Taiwan［J］. J Chin Med Assoc, 2010, 73(11): 596-598.
［8］Chen Y, Zhou Z, Jiang Y, Yu Y. Emergence of NDM-1-producing Acinetobacter baumannii in China［J］. J Antimicrob Chemother, 2011, 66(6): 1255-1259.
［9］Zhou Z, Guan R, Yang Y, Chen L, Fu J, Deng Q, et al. Identification of New Delhi metallo-beta-lactamase gene (NDM-1) from a clinical isolate of Acinetobacter junii in China［J］. Can J Microbiol, 2012, 58(1): 112-115.
［10］Deshpande P, Rodrigues C, Shetty A, Kapadia F, Hedge A, Soman R. New Delhi Metallo-beta lactamase (NDM-1) in Enterobacteriaceae: treatment options with carbapenems compromised［J］. J Assoc Physicians India, 2010, 58: 147-149.
［17］Struelens MJ, Monnet DL, Magiorakos AP, Santos OF, Giesecke J. New Delhi metallo-beta-lactamase 1-producing Enterobacteriaceae: emergence and response in Europe［J］. Euro Surveill, 2010, 15(46): 1-10.
［18］Poirel L, Dortet L, Bernabeu S, Nordmann P. Genetic features of blaNDM-1-positive Enterobacteriaceae［J］. Antimicrob Agents Chemother, 2011, 55(11): 5403-5407.
［19］Poirel L, Ros A, Carricajo A, Berthelot P, Pozzetto B, Bernabeu S, et al. Extremely drug-resistant Citrobacter freundii isolate producing NDM-1 and other carbapenemases identified in a patient returning from India［J］. Antimicrob Agents Chemother, 2011, 55(1): 447-448.
［20］Pfeifer Y, Witte W, Holfelder M, Busch J, Nordmann P, Poirel L. NDM-1-producing Escherichia coli in Germany［J］. Antimicrob Agents Chemother, 2011, 55(3): 1318-1319.
［21］Livermore DM, Mushtaq S, Warner M, Zhang J, Maharjan S, Doumith M, et al. Activities of NXL104 combinations with ceftazidime and aztreonam against carbapenemaseproducing Enterobacteriaceae［J］. Antimicrob Agents Chemother, 2011, 55(1): 390-394.
［22］Docobo-Perez F, Nordmann P, Dominguez-Herrera J, Lopez-Rojas R, Smani Y, Poirel L, et al. Efficacies of colistin and tigecycline in mice with experimental pneumonia due to NDM-1-producing strains of Klebsiella pneumoniae and Escherichia coli［J］. Int J Antimicrob Agents, 2012, 39(3): 251-254.
