【摘要】 为研究鸭源大肠杆菌(E.coli)的致病性,明确鸭病原性E.coli与人和其他动物E.coli的亲缘关系及O血清型与菌种间遗传关系的相关性,本研究从我国西南地区规模化养鸭场患典型E.coli败血症的雏鸭体内分离37个血清型共82个E.coli分离株(其中优势血清型32株,其他血清型50株),以每株0.2 mL(l09 cfu/mL)腿部肌肉接种7日龄健康鸭进行致病性试验;并对其中14个鸭源E.coli代表株进行16S rRNA基因克隆、测序及系统发育分析。结果表明:所有分离株全部为致病性E.coli,其中高致病株、中等致病株和低致病株分别占受试菌株的80.5%(66/82)、17.1%(14/82)和2.4%(2/82),4个优势血清型全部为高致病株和中等致病株,分别占受试菌株的84.4%(27/32)和15.6%(5/32);14个代表株鸭源E.coli的16S rRNA形成2个主要分支,3株新发现的血清型单独形成一个较远的分支,11株常见血清型与人及其他动物源E.coli形成另一个大的分支,其中有6株与人的O157亲缘关系较近,2株与出血性E.coli O157∶H7 sakai聚为一个小分支;从遗传进化的关系分析,这些菌株有可能是人类的潜在病原菌;同时还发现不同血清型的分离株可以聚为一支,而同一血清型的分离株可以处于不同的分支,常规的O血清学分型不能体现菌种间遗传关系的远近。更多还原

【Abstract】 To investigate the pathogenicity of duck pathogenic E.coli and identify the genetic evolution relationship of these duck originated serotype O E.coli with that of human and other animals,a total of 82 E.coli isolates were isolated from ducklings with typical clinical signs of E.coli infection on large-scale duck farms in 8 areas of southwest China,and those isolates were classified into 37 kinds of O serotypes,of which the dominant serotypes accounted for 32 isolates and 50 isolates for other serotypes.The pathogenicity of all isolates was evaluated in 7-day old ducklings by leg intramuscular inoculation with each isolate at 0.2 mL of 109 cuf/mL.The results showed that all isolates were pathogenic to mice and the high,intermediate and low-pathogenicity isolates were accounted to 80.5%(66/82),17.1%(14/82) and 2.4%(2/82),respectively.The phylogenetic analysis based on 16S rRNA sequences demonstrated that the 14 representative isolates in 82 islotes were divided into 2 clusters,of which 3 isolates formed in an individual branch beyond others and other 11 isolates were gathered into another bigger branch with reference E.coli strains from human and animals,6 of the 11 isolates had a close relationship with E.coli serotype O157 of human in which 2 isolates were gathered into one branch with O157∶H7 Sakai strain,from the point of genetic evolution these 6 isolates might be the potential pathogenic bacteria for human.The phylogenetic analysis also showed that the isolates with different serotypes were gathered into one branch,while some isolates with same serotypes were gathered into different branches,which indicated that the typing method according to serotype O was not related to the genetic relationship of E.coli strains.更多还原