大肠埃希菌质粒介导的bla_(NDM-1)基因耐药及传播性研究

目的探讨某院携带bla_(NDM-1)基因大肠埃希菌的流行现况及传播机制。方法收集2016年1—12月南昌大学某附属医院对碳青霉烯类抗生素不敏感的大肠埃希菌92株,对其进行bla_(NDM-1)基因筛查,并对bla_(NDM-1)基因阳性的大肠埃希菌进行其他常见碳青霉烯酶基因检测。将bla_(NDM-1)基因阳性的大肠埃希菌(供体菌)与大肠埃希菌J53(受体菌)进行接合试验,采用药敏试验及mCIM试验对接合子进行表型验证,提取供体菌及接合子的质粒采用Southern blot技术对bla_(NDM-1)基因进行基因定位,并验证其水平转移的能力。结果在对碳青霉类抗生素不敏感的92株大肠埃希菌中发现2株携带bla_(NDM-1)基因,携带率2.2%。此2株大肠埃希菌未发现同时携带其他常见碳青霉烯酶基因。接合试验及Southern blot发现此2株大肠埃希菌的bla_(NDM-1)基因均位于菌株的质粒上,且有1株大肠埃希菌的bla_(NDM-1)基因可以通过质粒向大肠埃希菌J53转移。药敏试验结果显示,此2株大肠埃希菌对临床使用的多种抗菌药物耐药,且接合子获得了与供体菌相似的药敏结果。mCIM试验表明,此2株大肠埃希菌及接合子均产NDM-1型碳青霉烯酶。结论该院存在携带bla_(NDM-1)基因而产NDM-1型碳青霉烯酶的大肠埃希菌,携带bla_(NDM-1)基因的大肠埃希菌对临床使用的大多数抗菌药物耐药,质粒可介导bla_(NDM-1)基因的水平传播。

Plasmid-mediated blaNDM-1 gene resistance and transmission of Escherichia coli

Objective To investigate the epidemic status and transmission mechanism of bla_NDM-1 gene-carrying Escherichia coli(E. coli) in a hospital. Methods 92 strains of carbapenem-non-susceptible E. coli were collected from a hospital affiliated to Nanchang University between January and December 2016, bla_NDM-1 gene was screened and other common carbapenemase genes in bla_NDM-1 positive E. coli were also detected. bla_NDM-1 positive E. coli (donor) and E. coli J53 (receptor) was performed conjugation testing, phenotyping of conjugants was validated by antimicrobial susceptibility testing and modified carbapenem inactivation method(mCIM), plasmids of donor strain and conjugator were extracted, bla_NDM-1 gene was located by Southern blot, and horizontally transfer ability of bla_NDM-1 gene was validated. Results Among 92 strains of carbapenem-non-susceptible E. coli, 2 strains were found to carry bla_NDM-1 gene, carrying rate was 2.2%. Other common carbapenemase genes were also found in these two strains of E. coli. Conjugation testing and Southern blot found that bla_NDM-1 gene of these two E. coli strains was located on the plasmid of E. coli strain, and bla_NDM-1 gene of one E. coli strain could be transferred to E. coli J53 through plasmid. Antimicrobial susceptibility testing showed that these two E. coli strains were both resistant to multiple clinically used antimicrobial agents, conjugants obtained similar susceptibility results to the donor bacteria. mCIM showed that these two E. coli strains and their conjugants all produced NDM-1 carbapenemase. Conclusion E. coli carrying bla_NDM-1 gene and producing NDM-1 carbapenemase is found in this hospital, E. coli carrying bla_NDM-1 gene is resistant to most clinically used antimicrobial agents, plasmids can mediate the horizontal transfer of bla_NDM-1 gene.