iss基因与鸡大肠杆菌致病力的关系

Relationship between iss gene and the virulence of avian Escherichia coli

为探讨iss基因的存在及其核苷酸序列的差异与鸡大肠杆菌致病力的关系,分别采用普通PCR及套式PCR方法检测iss基因在21株鸡大肠杆菌菌株中的分布,并进行序列测定,分析菌株携带iss基因的情况及不同毒力的菌株间iss基因序列的差异。结果显示,经套式PCR检测21株鸡大肠杆菌均携带iss基因,而普通PCR检测显示仅有13株携带iss基因;16株菌株iss基因与国外禽大肠杆菌iss基因参考序列同源性为100%;其余5株中,E1与参考序列同源性为93.5%,E33、O78与参考序列同源性为99.4%,E4、E21与参考序列同源性为99.7%。推测,iss基因可能在不同来源、不同毒力、不同血清型的鸡大肠杆菌中都普遍存在,仅是拷贝数高低不同,而不是目前普遍认为的"有或无"的关系,并且iss基因序列是高度保守的。iss基因与鸡大肠杆菌致病力的相关性可能与它所定位的质粒拷贝数有关,与iss基因的序列差异无关。

The presence of iss gene was tested by amplification, and the sequences of studied strains were analyzed in comparison with AF042279 in GenBank（iss gene from avian Escherichia coli isolate）. It was found that all of the 21 isolates had iss gene,which was different from the other isolates. Amplification of iss gene might be related to the copy-number of plasmid,in which iss gene was located. Each iss gene from 16 of 21 isolates shared 100% identity,and E1 shared 93.5% identity with AF042279 in GenBank,re-spectively. Each from E33 and O_（78） shared 99.4% identity, and E4 and E21 shared 99. 7% identity with AF042279 in GenBank, respectively. It suggested that iss gene might be highly conserved. And iss gene might be related to the virulence of avian E. coll. Relationship between iss gene and virulence of avian E. coli might be associated with the copy-number of iss,not its sequence.