六十二株水貂源大肠杆菌分离株耐药表型与耐药基因及克隆菌群分析

为了调查诸城地区某水貂养殖场粪便源大肠杆菌的表观及其分子特征，采集某个水貂养殖场的水貂粪便进行大肠杆菌分离鉴定，对分离鉴定的大肠杆菌进行血清型鉴定和对14种常见抗菌药物的耐药表型鉴定；使用PCR检测耐药基因以及Ⅰ整合子基因盒的携带情况，利用多位点序列分型（MLST）来分析菌株的克隆关系并构建系统发育树来分析相同克隆群菌株的遗传相似性。结果显示，自82份水貂粪便样品分离到62株大肠杆菌，分离率75.61%；大肠杆菌分离株对AMP和TET的耐药率超过90%，多重耐药菌株（MDR）占比为85.48%。PCR检测到5类耐药基因的存在，qnrS检出率最高，为61.29%（38/62）；aaC2、aaC4、sul1和aac（6'）-Ib-cr耐药基因与菌株产生相应的耐药抗性存在一致性（P<0.01）。分离菌株中Ⅰ类整合子可变区域的优势结构为dfrA27-aadA2-qnrA。鉴定出致病性血清型的存在，且对应菌株都具有多重耐药性，优势血清型为O104：H4。分离株中存在33个STs，ST46为优势STs（16.13%），具有3个主要克隆群，依次为CC10、CC46和CC176；与致病性相关菌株的STs和人源大肠杆菌具有共同的遗传背景。本研究表明，养殖场的水貂受到致病性和多重耐药性大肠杆菌的污染，相同克隆群菌株的耐药基因分布具有多态性，表观特征差异明显。

Analysis of Drug Resistance Phenotype,Drug Resistance Genes and Cloned Flora of 62 Mink-derived Escherichia coli Isolates

This experiment was conducted to investigate the apparent characteristics and molecular characteristics of Escherichia coli isolates from the feces of a mink farm in Zhucheng. Mink feces from the mink farm were collected for isolating E. coli strains, then the isolates were identified, and their serotypes and drug resistance phenotypes to 14 common antibacterial drugs were determined. The drug resistance genes and the carrying status of the Ⅰ integron gene cassette of these E. coli isolates were detected by using PCR. Multi-locus sequence typing (MLST) was used to analyze the clonal relationship of these strains,and a phylogenetic tree was constructed to analyze the genetic similarity of the same clonal strains. The results showed that 62 strains of E. coli were isolated from 82 samples of mink feces, with a separation rate of 75.61%, and the resistance rate of E. coli isolates to AMP and TET exceeded 90%, and the multidrug-resistant strain (MDR) accounted for 85.48%. Five drug-resistant genes were detected by PCR, and the detection rate of qnrS was the highest (61.29%,38/62). The aaC2, aaC4, sul1 and aac(6')-Ib-cr resistance genes were consistent with the corresponding resistance of these strains (P<0.01). The dominant structure of the class Ⅰ integron variable region in the isolated strain was dfrA27-aadA2-qnrA. The pathogenic serotype was identified and the corresponding strains had multiple drug resistance. The dominant serotype was O104:H4. There were 33 STs in the isolates, and ST46 was the dominant ST (16.13%). There were 3 main clones, CC10, CC46 and CC176, respectively. The STs strains associated with pathogenicity share a common genetic background with human E. coli. The results showed that the mink of the farm were contaminated by pathogenic and multi-drug resistant E. coli. The distribution of drug resistance genes in the same clonal strains showed significant differences in polymorphism and epigenetic characteristics.