本研究采集广州某规模化养殖场腹泻仔猪、健康仔猪及环境样本共147份，据国标GB 4789.6-2016分离鉴定大肠杆菌，用K-B法分析分离株对12种抗生素的敏感性，并用PCR检测其对应的耐药基因。结果共检出大肠杆菌115株；分离菌株依次对复方新诺明，左氧氟沙星、加替沙星、环丙沙星呈高水平耐药，耐药率 > 30%；对庆大霉素、头孢他啶、氨曲南也呈现一定水平耐药（20%~30%）；对多粘菌素B、替加环素、亚胺培南耐药水平较低（< 15%），对美罗培南敏感；46.09%菌株呈现多重耐药（≥ 3种抗生素），且腹泻仔猪源菌株多重耐药率显著高于健康仔猪源及环境源菌(p < 0.05)。分离株耐药基因携带严重，其中ant(3'')-Ⅰa、aac(3')-Ⅰb、sul1、aac(3)-Ⅱb，blaTEM、blaCTX、tetM基因检出率 > 50%，因此，这可能是本研究菌株的主要耐药机制。研究结果表明该养殖场大肠杆菌污染严重，耐药水平高，有关部门需加强养殖中腹泻仔猪防治用药的监管与指导。

This research investigated 147 samples collected from diarrhea pigs, healthy pigs and environment of a large-scale farm in Guangzhou. Escherichia coli strains were isolated and identified according to GB 4789.6-2016, and their susceptibility to 12 antibiotics and corresponding resistance genes were analyzed using the K-B disc diffusion method and polymerase chain reaction (PCR), respectively. Results revealed a total of 115 strains of E. coli. Drug resistance to sulfamethoxazole, levofloxacin, gatifloxacin and ciprofloxacin was high (over 30%), to gentamicin, ceftazidime and Aztreonam was moderate (20%~30%), and to polymyxin B, tigecycline and imipenem was relatively low (< 15%), with sensitivity to meropenem also detected. Multi-drug resistance (resistance to strains ≥ 3) was observed in 46.09% strains, with the strains from the diarrhea pigs being more resistant than those of the healthy pigs and environmental samples (p < 0.05, χ2-test). The isolated strains carried high levels of genes encoding resistance to drugs, among which the detection rates of ant(3'')-Ⅰa, aac(3')-Ⅰb, sul1, aac(3)-Ⅱb, blaTEM, blaCTX, tetM genes over 50%, thus suggesting the major resistance mechanism for the strains isolated in this study. The results of present study indicated the serious contamination with E.coli strains in this farm and their high antibiotic resistance. Relevant departments should provide supervision and guidance on the use of appropriate antibiotics for the effective prevention and treatment of diarrhea pigs.

国家自然科学基金项目（31571934）；广东省科技计划项目（2014A020214001、2016A020219001）；中央高校基本科研业务费（D2170320）；中央高校建设世界一流大学（学科）和特色发展引导专项资金（K5174960）；中国博士后科学基金项目（2016M590785）