四川阿坝州牦牛源溶血性大肠杆菌血清型鉴定及毒力相关基因检测

Serotype Identification and virulence-related genes detection of hemolytic E.coli isolated from yak in Sichuan Aba state

为了解牦牛源溶血性大肠杆菌血清型及毒力相关基因,本研究从四川阿坝州采集的牦牛鼻腔棉拭子中分离鉴定溶血性大肠杆菌,并通过玻板凝集结合试管凝集试验鉴定其血清型,采用PCR方法检测大肠杆菌的4个溶血素基因及其它7个毒力相关基因。结果显示,从临床健康的牦牛鼻腔中分离鉴定出74株溶血性大肠杆菌,分离率为19.2%(74/386)。O血清型鉴定结果显示,74株牦牛源溶血性大肠杆菌中已确定O血清型的菌株有60株,共24种O血清型,其余14株未能定型。PCR检测与溶血素相关的4个基因携带率分别为96.0%(hly A)、86.5%(hly E)、14.9%(ehly)和2.7%(ehx);有4种溶血素基因组合,分别为hly A^+(96.0%),hly E^+(86.5%),hly A/hly E双阳性(80.9%),ehx/hly E双阳性(2.7%);其它毒力相关基因的检出率分别为93.2%(irp2)、93.2%(fyu A)和2.7%(stx2);LT、STa、STb和K99基因未检出。研究结果表明,溶血性大肠杆菌存在于临床健康牦牛鼻腔内,血清型复杂且无优势血清型,大肠杆菌溶血素相关基因和高致病性毒力岛相关基因携带率高。本研究首次对四川阿坝州牦牛源溶血性大肠杆菌的血清型和毒力相关基因进行了研究,提示在牦牛中存在溶血性大肠杆菌的潜在威胁。

To identify the serotypes and detect the virulence-related genes of hemolytic E.coli isolated from yak, the haemolytic E.coli were isolated and identified from the nasal swabs of yak in Sichuan Aba state. The serotypes were identified by plate agglutination combined with tube agglutination tests, and the 4 hemolytic genes and 7 virulence-related genes of E.coli were detected by PCR. The results showed that 74 strains of hemolytic E.coli were isolated and identified from nasal cavity of clinical healthy yak with the isolation rate of 19.2% （74/386）. E.coli O serotype identification showed that there were 24 kinds of O serotype in 60 isolates and the other 14 strains could not be identified. The carrying rate of the four hemolysin-related genes were 96.0% （hlyA）, 86.5% （hlyE） （86.5%）, 14.9% （ehly） and 2.7% （ehx）, respectively. There were four hemolysin gene combinations, such as hlyA＋ （96.0%）, HlyE＋ （86.5%）, hlyA＋/hlyE＋ （80.9%）, and ehx＋/hlyE＋ （2.7%）. The detection rates of other virulence- related genes were 93.2% （irp2）, 93.2% （fyuA） and 2.7% （stx2）, respectively, and LT, STa, STb and K99 genes were not detected. The result indicated that hemolytic E.coli existed in the nasal cavity of healthy yak with complicated serotypes and had no dominant serotypes. There were high carrying rates of hemolysin-related virulence genes and high pathogenicity virulence island-related genes in hemolytic E.coli in healthy yak. In this study, the serotypes and virulence-related genes of yak derived hemolytic E.coli in Aba state, Sichuan, were studied for the first time, suggesting the potential threat of hemolytic E.coli in yak.