Serum resistance associated with virulence in Yersinia enterocolitica

Abstract

Y. enterocolitica strains that exhibited a Ca requirement for growth and autoagglutination at 37.degree. C were invariably virulent in rabbits, causing diarrhea and a high degree of lethality, and were capable of colonizing the intestinal lumen and establishing foci of infection on the Peyer''s patches of mice. Strains that had lost the properties of Ca dependency and autoagglutinability were totally avirulent in rabbits and were quickly eliminated from the intestinal lumen and tissues of mice. Virulent and avirulent strains were shown to be equally invasive to human cervical carcinoma HeLa cells. The virulent strains were resistant to the bactericidal action of normal serum; this serum resistance was lost with the loss of virulence. The serum resistance of virulent strains was expressed, as were other properties, when strains were grown at 37.degree.C, but not at 25.degree. C. Thus, a virulence factor, associated with serum resistance, seemingly plays an essential role in the pathogenicity of Y. enterocolitica.