牛肠道大肠杆菌的分离鉴定及耐药性分析

Isolation,Identification and Drug-resistance Analysis of E.Coli from Calves

【目的】新疆昌吉市周边某牛场大量犊牛严重腹泻,排黄色水样稀便,有的带血,并出现精神萎靡、食欲不振等症状,为确定此次发病的病原并提供治疗参考。【方法】通过对该牛场出现的犊牛腹泻粪样进行细菌鉴定及分型并进行耐药性分析。【结果】PCR鉴定结果显示为大肠杆菌阳性,染色镜检结果符合大肠杆菌形态特征,分离菌株具有K99黏附性基因。药敏试验结果显示该分离菌株仅对多黏菌素B中介(既不敏感也不耐药),对其他所有受试抗菌药物耐药。在致病性试验中,小鼠在15 h内陆续死亡,说明该菌株具有一定致病力。【结论】结果表明,该牛场犊牛腹泻粪便中分离的菌株为产肠毒素性大肠杆菌,携带K99毒力基因,对多黏菌素B中介,具有一定致病力。

【Objective】The study aimed to identify the pathogen responsible for the recent outbreak of severe diarrhea,characterized by yellow watery stool,some with blood,and symptoms like depression and loss of appetite among calves in a cattle farm near Changji City,Xinjiang Province,and to provide a basis for treatment.【Methods】The research involved bacterial identification and classification from the diarrheic fecal samples of calves,as well as an analysis of drug resistance.【Results】The findings indicated that the pathogenic bacterium was identified as Escherichia coli.PCR analysis confirmed the presence of E.coli,and the staining microscopy was consistent with its morphology,including the presence of the K99 adhesive gene in the isolated strain.Drug susceptibility testing revealed that the bacteria were resistant to polymyxin B but susceptible to other tested antimicrobial agents.Pathogenicity tests on mice resulted in death within 15 hours,thereby proving the strain’s pathogenic capacity.【Conclusion】The isolated strain from the diarrheic feces of calves was determined to be enterotoxigenic E.coli(ETEC),harboring the K99 virulence factor,and demonstrated pathogenicity,particularly showing resistance to polymyxin B.This discovery is critical for guiding effective treatment strategies.