鸭源大肠杆菌的分离鉴定及致病性分析

【目的】 了解江苏、江西、安徽地区鸭源大肠杆菌的分布以及致病性情况。【方法】 本研究对江苏、江西、安徽地区的病死鸭进行了鸭源大肠杆菌的分离鉴定，运用PCR结合玻片凝集法测定鸭源大肠杆菌分离株的血清型，并进行了18种毒力基因的PCR检测，随后进行雏鸭致病性试验，并对毒力较强和毒力较弱的菌株进行生长曲线以及半数致死量(LD₅₀)测定。【结果】 本研究共分离鉴定获得鸭源大肠杆菌74株，鉴定为O1、O2、O18、O78血清型的分别有1、2、2和4株，其余均未定型;18种毒力基因鉴定结果表明，ibeB、yijp、OmpA和mat基因检出率分别为97.3%、97.3%、95.95%和90.54%。动物致病性试验结果表明，经10⁷ CFU/只攻毒后，74株分离株均引起雏鸭不同程度发病，但仅有2株对雏鸭致死率≥50%。生长曲线测定结果表明，2株强毒株与2株弱毒株的生长速度无显著差异(P>0.05)，2株强毒株的LD₅₀分别为10^4.75和10^7.375 CFU。【结论】 本研究分离的74株鸭源大肠杆菌O1、O2、O18和O78型仅占12.16%，毒力基因谱分布广泛，但仅有2株毒力较强，该研究为鸭源大肠杆菌病的预防控制以及研究血清型、毒力基因与致病性之间的相互关系奠定基础。

Isolation,Identification and Pathogenicity Analysis of Escherichia coli from Ducks

【Objective】 This study was aimed to understand the distribution and pathogenicity of Escherichia coli from ducks in Jiangsu,Jiangxi and Anhui provinces.【Method】 This study isolated and identified duck derived Escherichia coli from dead ducks in Jiangsu,Jiangxi and Anhui,determined the serotype of duck derived Escherichia coli isolates by PCR combined with slide agglutination,detected 18 virulence genes by PCR,and then carried out the pathogenicity test of ducklings.The growth curve and median lethal dose (LD₅₀) of the strains with strong and weak virulence were determined.【Result】 A total of 74 strains of duck derived Escherichia coli were isolated and identified in this study,1,2,2 and 4 strains were identified as O1,O2,O18 and O78 serotypes respectively,and the rest were not finalized.The identification test of 18 virulence genes showed that positive rates of genes ibeB,yijp,ompA and mat were 97.3%,97.3%,95.95% and 90.54%,respectively.Animal pathogenicity tests showed that 74 strains of Escherichia coli isolates were pathogenic to ducklings at infection dose of 10⁷ CFU/duck,but only 2 strains of isolates caused the death rate of ducklings ≥50%.The growth curve detemination showed that there was no significant difference between 2 strains of virulent isolates and 2 strains of attenuated isolates (P>0.05),and the LD₅₀ of 2 strains of virulent isolates were 10^4.75and 10^7.375 CFU,respectively.【Conclusion】 The rate of serotypes O1,O2,O18,O78 in 74 isolates was only 12.16%.The virulence gene spectrum was widely distributed,but only 2 strains of isolates were more virulent.This study laid the foundation for the prevention and control of Escherichia coli from ducks,it was also helpful for studying the relationship among serotypes,virulence genes and pathogenicity.