Characteristics and pathogenicity of non-melibiose-fermenting strains of Yersinia pseudotuberculosis O3

The biological properties of non-melibiose-fermenting (NMF) strains of Yersinia pseudotuberculosis O3 were investigated. These strains were clearly distinguished from representative melibiose-fermenting (MF) strains of Y. pseudotuberculosis O3 by their pathogenicity in mice, sensitivity to some phages, production of catalase, restriction endonuclease analysis of virulence plasmid DNA with BamHI, detection of specific yersinia outer-membrane proteins with SDS-PAGE, antigenicity of the outer-membrane proteins and neutrophil resistance to phagocytosis. The pathogenicity of NMF strains was clearly less than that of MF strains. In addition, the resistance of NMF strains to phagocytosis and catalase activity was evidently weaker than that of MF strains. These results suggested that the difference of pathogenicity was due to the ability of catalase production. Although the relationship between the above characteristics and melibiose-fermentation was not analysed, the pathogenicity of Y. pseudotuberculosis O3 strains can probably be predicted by testing melibiose-fermentation and catalase production.