Construction Of SLT-Ⅱe Gene Mutant Strain Of Escherichia Coli Causing Porcine Edema Disease

Edema disease (ED) of weaning piglets is mainly caused by Verotoxigenic Escherichia coli(VTEC) which lead to tetraplegia,titubation,spasm and coma. It's named "Edema disease"because edema of the stomach submucosa and the mesentery is often a prominent feature of thedisease. Following the reseachs of these years, people become grasp the pathopoiesis mechanismof edema disease. Fimbriae F18ab and variant of the SLT-â…¡e toxin were two pathogenic factors ofVTEC. The SLT-â…¡e toxin is mainly virulence to weaning pigs. So recombination of SLT-â…¡e geneis important to prevent the ED, and provide a good candidate of a live attenuated vaccine strain toprotect against ED.In this study, we replaced glutamate with glutamine at position 167 and arginine with leucineat position 170 of the A subunit, and then by homologous recombination, the SLT-â…¡e~* genewhich was inserted into the suicide plasmid pCVD442 was replaced with the SLT-â…¡e gene of thewild type virulent strain.We used 4 to 6 weeks old cleaning kunming mice and Vero cell to detect the virulence ofmutant strain, the result indicated that the tissue lesion to mice of mutant strain was much lighterthan that of wild strain, and the virulence to Vero cell is 1/500 of wild strain.