断奶仔猪源大肠杆菌F18菌毛的分子流行病学研究

Detection and molecular epidemiology of fimbriae F18 in the Escherichia coli strains isolated from weaned swine in China

利用F18菌毛a因子单克降抗体以及已建立的鉴定F18菌毛及其亚型的双重PCR法,对来自断奶仔猪水肿病和/或腹泻病例的60株VTEC、24株VTEC/ETEC以及24株ETEC的进行了F18菌毛检测,以了解F18ab+和F18ac+大肠杆菌在江苏省断奶仔猪群的分子流行病学。结果表明:通过F18菌毛a因子单克隆抗体,可检测出52株大肠杆菌为F18+,检出率为48.15%;而通过双重PCR方法,共检测出63株大肠杆菌为F18+,检出率为58.33%,其中53株(49.07%)为F18ab+,10株(92.6%)为F18ac+。另外还发现:在VTEC、VTEC/ETEC以及ETEC的菌株之间,这2种F18菌毛亚型的分子流行病学是不同的。在VTEC中,F18ab+,菌株37株(61.67%),未发现F18ac+菌株;在VTEC/ETEC中,F18ab+菌株15株(62.50%),Fl8ac+菌株8株(33.33%);而在ETEC中F18ab+菌株只有1株(4.17%),F18ac+菌株只有2株(8.33%)。以上数据表明:①PCR法检测F18菌毛优于单抗法;②FI8菌毛是VTEC/ETEC、VTEC的重要致病因子,而在ETEC中则明显低于VTEC/ETEC和VTEC;③F18ab+菌株—般为SLT-Ⅱe+,而F8ac+菌株一般为STI+。

To describe the distribution of fimbriae F18 in Escherichia coli strains isolated from weaned swine, Touch-down du-plex PCR and direct agglutination test by using monoclonal antibody （McAb） recognizing the common antigenic determinant ＂a＂of F18 were developed. 84 verotoxigenic Escherichia coli （VTEC）and 24 Enterotoxigenic E. coli （ETEC）from edematous and / or diarrheic weaned swines in different farms from different areas of China were tested for by using direct agglutination were F18ab positive and 10 the presence of F18,and the data show that 50 strains（46.03 %）were F18-positive in vitro test, and 63 strains （58.33 %） were positive for F18 gene,thereinto,53 strains （49.07 %） strains （9.26 %） were FlSac positive. In addition,the characteristics of VTEC and VTEC/ETEC strains were generally different from ETEC strains.The VTEC,VTEC/ETEC and ETEC strains with the F18ab gene present were 61.67 %,62.50 % and 4.17 %,respectively. Whereas the VTEC/ETEC strains with The F18ac gene present（33.33 %）were more frequently detected than in ETEC and VTEC strains（8.33 % and 0 respectively）. This paper indicated that： （1）PCR is an usefifl diagnostic tool in F18 detection,because it is quick, specific,sensitive ,and relatively inexpensive than direct agglutination test by using anti-F18 monoclonal antibody, （2）F18 is a important virulent factor in VTEC and VTEC/ETEC other than in ETEC, （3）F18ab are frequently associated with SLT-IIe,whereas F18a care frequently associated with STI.