[Experimental pathogenicity of "Yersinia enterocolitica" for athymic nude mice (author's transl)].

Amongst the 4,500 strains of our collection of Yersinia enterocolitica usually non-pathogenic for laboratory animals, 5 or 6 strains appeared to be naturally pathogenic for mice. Using these strains and non-pathogenic strains representing more than 90 per cent of human isolates in the world (biotype 4, serotype 0:3, phagocyte VIII; biotype 2, serotype 0:9, phagotype X3), the pathogenicity for cyclophosphamid treated mice and athymic Nude mice has been tested. Highly pathogenic strains killed conventional as well as cyclophosphamid treated mice. Non-pathogenic strains for conventional mice did not show any pathogenicity for cyclophosphamid treated mice (strain IP161 excepted) but killed 30 athymic Nude mice inoculated with 5 x 10(8) and 5 x 10(5) organisms by the oral or intraperitoneal routes. Nude mice infected intragastrically or intraperitoneally showed signs of enteritis and bronchopneumonia followed by a septicemia. Abscesses were found in the liver, the spleen and the ileal wall. The infection of Nude mice with Y. enterocolitica resembles naturally acquired human infection where 2/3 of the cases are enteritis among under 4-year-old children and where septicemia occurs among immunologically deficient adults. The role of T-lymphocytes and of immune functions in Y. enterocolitica infection is discussed through our model.