江苏地区奶牛场bla NDM阳性大肠杆菌的分子流行病学

Molecular epidemiological study on bla NDM-positive Escherichia coli in dairy farms in Jiangsu province

为了调查江苏地区奶牛场大肠杆菌中blaNDM基因的分子流行病学特征。从江苏部分地区3个奶牛场采集样品134份,使用PCR和测序的方法筛选blaNDM阳性大肠杆菌,同时对其进行超广谱β-内酰胺酶类基因的检测,采用药敏试验检测blaNDM阳性大肠杆菌对19种常用抗生素的敏感性,通过多位点序列分型(MLST)和脉冲场凝胶电泳(PFGE)对携带NDM基因的大肠杆菌进行亲缘关系分析,通过质粒结合试验验证blaNDM基因的可转移性。结果显示,从134份奶牛场样品中共分离15株blaNDM阳性大肠杆菌,包括NDM-1和NDM-52种变体。15株blaNDM阳性大肠杆菌对多种抗生素均呈现不同程度的耐药,奶牛场15株blaNDM阳性大肠杆菌包括7种ST型,分别是ST410、ST846、ST206、ST101、ST1642、ST3076、ST1626,同一种ST型在粪便样品和环境样品中同时存在,表明相同ST型blaNDM阳性大肠杆菌可在动物与环境间相互传播。PFGE试验结果表明,15株blaNDM阳性大肠杆菌可以分为11个簇,同一样品的分离株倾向于相同的簇,在比较小的范围内存在PFGE图谱相同的现象;对15株菌株的结合子进行blaNDM基因的转移性试验结果表明,15株大肠杆菌的blaNDM耐药基因均通过质粒结合转移至受体菌J53。表明,blaNDM阳性大肠杆菌在江苏省部分地区奶牛场中流行相对较为严重,存在多重耐药现象,推测blaNDM基因主要通过质粒结合转移的方式进行水平传播,这为食品源耐药菌的监测及风险评估提供了依据。

To investigate the epidemiology and molecular characteristics of blaNDM gene in Escherichia coli from dairy farms in Jiangsu province,a total of 134 samples were collected from three dairy farms in Jiangsu province.The blaNDM-positive E.coli was screened using PCR and sequencing,and the extended-spectrumβ-lactamase gene was detected.The antimicrobial susceptibility testing was used to detect the sensitivity of blaNDM-positive E.coli to 19 commonly used antibiotics.The genetic relationship of E.coli carrying NDM gene was analyzed by multi-locus sequence typing(MLST)and pulsed-field gel electrophoresis(PFGE).The transferability of blaNDM gene was verified by conjugation experiments.The results showed that fifteen strains of blaNDM-positive E.coli were isolated from 134 dairy samples,including NDM-1 and NDM-5.All fifteen strains of blaNDM-positive E.coli exhibited different resistance to multiple antimicrobials and belonged to seven STs,namely ST410,ST846,ST206,ST101,ST1642,ST3076,ST1626.The same ST was involved in both fecal and environmental samples,indicating that blaNDM-positive E.coli with the same type of ST could be transmitted from animals to environment.The results of PFGE showed that fifteen strains of blaNDM-positive E.coli could be divided into 11 clusters,isolates of the same sample tended to have the same PFGE cluster,and the same PFGE pattern existed in a relatively small range.The blaNDM gene of fifteen strains of E.coli was transferred to receptor bacterium J53 by binding with plasmids.The blaNDM-positive E.coli is relatively more prevalent in dairy farms in Jiangsu,and there is multi-drug resistance.The blaNDM gene is mainly transmitted by means of combined transfer,which provides a basis for monitoring and risk assessment of drug-resistant bacteris.