| Summary |
Twenty-five strains of E. coli swine origin, were used to determine the production of heat-stable enterotoxin (ST) and heat-labile enterotoxin (LT) by means of rabbit intestine ligated test. Twelve of the strains produced ST, 9 strains LT, and 10 of the strains contained neither of the enterotoxin. Only 6 of them produced both kinds of
enterotoxins.
The OK antigens were prepared from individual culture of the strains. A concen tration of 10-12% transmittance by the photoelectric colorimeter (containing about 4-5 xl0' CFU /ml density) of the bacterin was employed to immunize the rabbit, two rabbits for each strain. Four boosters were performed at an interval of five days. Serum was collected one week after the last inoculation, and stored at -20° C befor use. The results of plate agglutination tests indicated that the hyperimmune serum reacted specifically and strongly with homologous strain, and some with heterologous strains with varying degree of intensity. The serum titers were varying from x200 to x25,600 by means of tube agglutination test.
It was noted that the antigen of strains Gl253 (0147: K89 K88ac) , E145 (0141: K85 ac) , E57 (0138 : K81) , V189 (0108 : K"V189") , and V50 (010 : K" V50") reacted with much more heterologous immune sera than those of othe rstrains.
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