多重耐药基因cfr在食品动物源大肠杆菌中流行特点的调查

Investigation of epidemic characteristics of multi-resistance gene cfr in Escherichia coli isolates from food animal origins

为调查多重耐药基因cfr在我国多个地区食品动物源大肠杆菌中的流行情况及耐药现状,对2014年从广东、山东、江苏等11个省份分离得到的4 702株大肠杆菌,采用PCR和测序方法验证cfr阳性菌株,并通过临床常用药物敏感性测定、脉冲场凝胶电泳分型（PFG E）和Southern杂交定位等方法,确定分离株的耐药表型和cfr基因在大肠杆菌中的传播方式。结果显示,共检出cfr阳性菌株9株,检出率为0.19%。药敏试验结果显示,9株cfr阳性菌株对氯霉素、氟苯尼考、氨苄西林、四环素、多西环素均耐药,对亚胺培南均表现为敏感,对庆大霉素、新霉素耐药率在60%以上,对其他药物耐药率介于10%~50%之间。PFGE结果显示,有2株来自同一养殖场的菌株谱型相似,表明存在克隆传播。Southern杂交结果显示,cfr基因定位于大小为70~400 kb之间的质粒上。上述调查结果表明,多重耐药基因cfr在食品动物源源大肠杆菌中的检出率较低,但在广东地区较为流行。

To investigate the epidemiology and dissemination mechanism of multi-resistance gene cfrin Escherichia coli isolates from food-producing animals in China,4 702 Escherichia coli isolates collected in 2014 from 11 provinces were detected. The cfr-positive strains were analysed by PCR and sequencing. The minimal inhibitory concentrations （MIC） were determined by the agar disk diffusion met- hod, with distinct Pulsed-field gel electrophoresis typing （PFGE） and the location of cfrgene was de- tected by Southern bloting. In result,9 strains were cfr-positive and the positive rate was 0.19%. 9 cfr-positive isolates were all resistant to chloramphenicol,florfenicol,ampicillin,tetracycline and doxycycline,respectively but were susceptible to imipenem. The resistant rate of 9 isolates to gentamycin and neomycin were over 60%,to the rest were between 10% and 50%. PFGE analysis showed that two strains from the same farm displayed almost the same PFGE type,suggesting the existence of clonaling dissemina- tion of cfr-positive Escherichia coli. Southern blot displayed that the cfr gene was located in plas- mids with size from 70 kb to 400 kb. In conclusion,the study shows that cfrgene displayed a lower detec-tion rate in Escherichia coli from food-producing animals and a higher prevalence in Guangdong,China.