猪源大肠埃希菌血清型O145菌株分离鉴定、耐药性及致病性研究

Isolation,identification and pathogenicity of porcine-originated Escherichia coli O145

大肠埃希菌是引起仔猪腹泻甚至死亡的最常见的细菌性病原体。本试验对辽宁某规模化猪场3日龄腹泻仔猪进行了细菌分离鉴定。结果显示:从腹泻仔猪肝脏中分离出革兰氏阴性杆菌,经16SrDNA基因扩增和序列测序比对,与CENBANK登录号为CP031919.1(血清型为0145大肠埃希菌)基因序列同源性为99.44%,表明分离菌株为血清型0145大肠埃希菌;动物试验结果:分离菌36h内引起感染小鼠全部死亡,说明分离菌株为强致病性大肠埃希菌;毒力基因检测结果:分离菌株携带iusD、iss、FimH等毒力基因;药敏试验结果:分离菌株对头孢噻敏感,对阿米卡星中敏,对多黏菌素B、头孢唑啉、阿奇霉素、阿莫西林、大观霉素、环丙沙星、红霉素、多黏菌素E、利福平、复方磺胺甲唑和多西环素等11种药物均呈现耐药;耐药基因检测:分离菌株携带aac(6')-Ⅰb、aac(3')-Ⅱ、TEM、qnrS、ermB等耐药基因。

Escherichia coli is the most common bacterial pathogens causing piglet diarrhea and inducing mortality.In the present study,bacteria were isolated and identified from 3-day-old diarrheal piglet in an intensive pig farms of Liaoning province.The results showed that gram-negative bacteria were isolated from the liver of the diarrheal piglet,which has 99.44%homology with Escherichia coli with the serotype of O145(login number CP031919.1 IN GENBANK)after 16S rDNA amplifications and sequencing,indicating the isolated bacterial strain was Escherichia coli O145.The animal experiment illustrated that all the mice infected with the isolated bacterial died in 36 hours,indicating the isolated bacterial strain was pathogenic Escherichia coli.The results of virulence genes detection showed that the isolated bacterial strain carried virulence genes including iusD,iss,Fim H etc.The results of drug sensitivity test showed that the isolated bacterial strain was sensitive to Cefotaxime,moderately sensitive to amikacin,and resistant to 11 drugs including polymyxin b,Cefazolin,Azithromycin,Amoxicillin,spectinomycin,Ciprofloxacin,erythromycin,polymyxin E,rifampicin,Compound sulfamethoxazole and doxycycline.The results of drug resistance gene test showed that the isolated bacterial strain carried resistant gene including aac(6')-Ⅰ b,aac(3')-Ⅱ,TEM,qnrS and ermB.