Biological Characteristics Of Tibetan Yak Escherichia Coli

Yaks,Escherichia coli is the serious damage disease to the breeding yak, According to the statistics, this disease incidence rate was 10.1%, mortality rate was 2.5%, death rate was 45.0%. By the complex serotype and antibiotics were used, drug-resistant strains increase,also bring the adverse effects for yak intestinal normal bacterium,to control and yaks health brings great difficulties and influence。Based on this, it is necessary to research the biological characteristics of disease pathogens, research the pathogenesis and regularity, laid a good foundation for the disease prevention。Yaks′Escherichia coli(Tibet–9903), by conventional culture methods, morphological staining, flagellum check and electron microscope observation, the culture characteristics and morphological are similar to the standard E. colii(C83907), in line with the characteristics of E. coli. By physiological and biochemical identification, the results are in line with the characteristics of the bacteria. Through the glass plate agglutination test and the test–tube agglutination test, the determination of the Tibet–9903 mixed with serotype O26,O142,O148 and O158.Tibet–9903 and C83907 were to get vaccinated in rabbit muscle, with highly pathogenic, mortality is 100%. From the death of the rabbit liver, spleen and heart's blood are able to separate the same bacterial strains as before.From Tibet–9903 and C83907 deadly rabbit blood smear, gram's staining and under the oil microscope, we can see Tibet–9903 and C83907 have strong adsorption of blood cells, each blood cell can adsorb about 13 Tibet–9903 or C83907 around.By strains Tibet–9903 and adhesin C83907 were determinationed, the red cell agglutination test spectroscopy shows that Tibet–9903 can agglutination rabbit erythrocyte, agglutination price at 29, and a narrow hemagglutinin spectrum, C83907 can agglutinate rabbits, chickens, ducks, pigs red blood cells, agglutination price at 29,211,28,28,and a broad hemagglutinin spectrum; Through made the bacterium hair intestinal epithelium cells brush border adhesion tests about strains Tibet–9903 and adhes C83907, the results showed that yak each intestinal epithelial brush border cells can absorption seven bacteria cells at least, they can be strong or stronger adhesion to the brush border cells.Making rabbit ligated ileum test of strains Tibet–9903 and adhesin C83907 the ability of LT production, found that the results both are positive, shows that possess the ability to produce LT, then,we used SDS–PAGE tests of the LT after purification are reliable, by SDS–PAGE electrophoresis patterns can be seen, both of molecular weight are 25 000Da and 12 500Da two bands, both are A and B subunit molecular weight of LT.Extracellular protease activity and hemolysin determination tests, the extracellular protease activity test results of strains Tibet–9903 and C83907 were positive, the hemolysin determination test results of the tow were no hemolysin, and the results were negative.Select the strains Tibet–9903 to preparation yaks ,Escherichia coli polyvalent oil–adjuvant inactivated vaccine, the quality inspection for qualified ,to field experiment, the results show that the vaccine–induced rabbit and yak clinical response a good immunogenicity. The vaccine laid the foundation for the prevention of the disease.