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In order to investigate the virulence of Y. enterocolitica isolated in Korea, all necessary experiments were done including several virulence determinating tests-autoagglutination test, calcium. dependency test, HeLa cell invasion test, Sereny test, crystal violet binding test, and electrophoresis for plasmid pattern. The obtained results are as follows:
The virulent strains of Y. enterocolitica revealed positive reactions on autoagglutination test, calcium-dependency test, and crystal violet binding test, while the aviraknt strains did not. A positive reaction was observed only at 37°C implying that the expression of virulence is temperature-dependent.
In Sereny test, the standard reference virulent strain (serotype 0:8) showed positive reactions while the virulent experimental strains (serotype 0:3, 0:9) revealed negative results, which indicates that the virulence of Y. enterocolitica in experimental animals varied according to their serotypes.
Most of the virulent strains contained 36-38Mdal plasmids, but the aviralent strains did not. In addition, it was noted that autoagglutination, caldum-dependency, and crystal violet binding were related to the presence of plasmids.
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