【摘要】 2020年8月从广东省某大型养鸡场不同区域采集粪便、土壤、水体等样品共654份，进行替加环素耐药大肠杆菌的分离鉴定；PCR方法检测替加环素耐药大肠杆菌的tet(X4)基因；PFGE分型检测tet(X4)阳性大肠杆菌的克隆传播情况；采用琼脂二倍稀释法和肉汤二倍稀释法测定tet(X4)阳性大肠杆菌的最小抑菌浓度(MIC);接合转移试验检测tet(X4)水平传播情况。结果显示，共分离得到204株替加环素耐药大肠杆菌，检测出165株tet(X4)阳性大肠杆菌，检出率为25.23%(165/654)。根据菌株来源和分离率，挑选72株进一步研究tet(X4)阳性大肠杆菌在该养鸡场的流行特征。PFGE分型将72株tet(X4)阳性大肠杆菌分为39个簇，表明该养鸡场无明显克隆传播现象。tet(X4)阳性大肠杆菌对替加环素的MIC范围为8～16 mg/L,且表现多重耐药表型，对四环素、多西环素、米诺环素、氨苄西林、氟苯尼考均表现高水平耐药，而对黏菌素、美罗培南均敏感。接合转移试验表明，tet(X4)阳性大肠杆菌主要位于IncHI1型质粒上(93.06%)。结果表明，tet(X4)基因在该养殖场主要随IncHI1质粒传播，提示应加强养殖场大肠杆菌tet(X4)的监测。更多还原

【Abstract】 In August 2020,a total of 654 samples of feces,soil and water were collected from different areas of a large chicken farm in Guangdong Province to isolate and identify tigecycline-resistant E.coli.The tet(X4) gene of tigecycline-resistant E.coli was detected by PCR.PFGE typing was performed to detect the cloning and transmission of tet(X4)-positive E.coli.The minimum inhibitory concentration(MIC) of tet(X4)-positive E.coli was determined by the agar dilution method and the broth dilution method.The horizontal spread of tet(X4) was detected by a conjugation transfer assay.The results showed that 204 strains of tigecycline-resistant E.coli were isolated and165 tet(X4)-positive E.coli were obtained with a detection rate of 25.23%(165/654).Based on the source and isolation rate,72 isolates were selected for further analysis of the epidemic characteristics of tet(X4)-positive E.coli in the chicken farm.PFGE patterns of 72 tet(X4)-positive E.coli were sorted into 39 clusters,indicating that there was no obvious clonal transmission in the chicken farm.The MIC range of tet(X4)-positive E.coli to tigecycline was 8-16 mg/L and showed multiple resistance phenotypes,with high levels of resistance to tetracycline,doxycycline,minocycline,ampicillin,and florfenicol,but sensitive to colistin and meropenem.The conjugation transfer assay showed that tet(X4)-positive E.coli were mainly located on IncHI1 plasmid(93.06%).The results showed that the tet(X4) gene was mainly transmitted through the IncHI1 plasmid in this farm,suggesting that tet(X4) surveillance of E.coli in farms should be strengthened.更多还原