Kiyomi Suzuki

Yersinia pseudotuberculosis in China

Thirty strains of Yersinia pseudotuberculosis were isolated from rabbits (17 strains), wild rats (9 strains) and house rats (4 strains) in China between 1990 and 1993. The biochemical properties of these isolates were identical with those of Y. pseudotuberculosis and no special characteristics were found in these strains. Serologically, serogroups 4b and 5b were identical to isolates found in Japan, and a new serogroup 1c and unclassified strains have also been detected. The existence of virulence‐associated properties were different among strains. The pYV plasmid was detected from 6 strains of 30 isolates. This report documents the presence of Y. pseudotuberculosis in China, providing important epidemiological information.

Characteristics and Pathogenicity of Non-Melibiose-Fermenting Strains of Yersinia pseudotuberculosis O3

The biological properties of non‐melibiose‐fermenting (NMF) strains of Yersinia pseudotuberculosis 03 were investigated. These strains were clearly distinguished from representative melibiose‐fermenting (MF) strains of Y. pseudotuberculosis 03 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 03 strains can probably be predicted by testing melibiose‐fermentation and catalase production.