Relationship between the Intracellular Multiplication of Salmonellae in Cultured Mononuclear Phagocytes and their Pathogenicity for the Host

The intracellular growth of various species of salmonellae was tested by the roller tube technique using cultured peritoneal macrophages from DK1 strain of mice which were selectively inbred by a uniform susceptibility to S. enteritidis infection. Intracellular growth was observed markedly with S. enteritidis, S. typhimurium and S. choleraesuis, but not at all with S. paratyphi A, S. typhosa (V and VW types), and also with Escherichia coli (0-55 type). Some strains of S. paratyphi B showed a slight intracellular growth when large numbers of phagocytes were examined. When those strains of S. paratyphi B were intraperitoneally inoculated into DK1 mice, large numbers of organisms were harbored in the peritoneal fluid and organs through the 3rd week compared with other strains of the same species and S. paratyphi A or S. typhosa. Histopathological findings of the liver of inoculated mice showed the formation of granulomas or typhoms, large and small, in the degree almost parallel to the number of harbored organisms. The coincidence between the apparent intracellular growth of bacterial species and their capability to produce typhoid infection in mice was emphasized.