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Genetically resistant CBA and A/J mice and susceptible BALB/c and C57BL/6 mice were challenged with either an identical infective dose or a minimal lethal dose of Salmonella typhimurium. The histopathological progression of the disease was examined in tissue sections prepared by the JB-4 Plus resin embedding method and compared between the resistant and susceptible mice. In a fatal disease, the lesions in both animal hosts began with focal abscesses within the first three days post infection. Mononuclear cell infiltration started by day 4 and transformed the lesions into granulomata. Well-formed granulomata were evident by day 7 and persisted in sublethally infected resistant mice. Massive bacterial proliferation and extensive tissue degeneration marked the terminal stage of a lethal challenge. There were no distinguishable features that would identify the tissue response to infection in a resistant host from a susceptible one, except that the lesions in the sublethally infected resistant mice advanced slower and were discrete and self-limiting.

SUMMARYThe ELISA was used to titrate the antibody response in mice inoculated with salmonella antigens. The genetically resistant A/J and susceptible C57BL/6J mice were either infected with the virulent or the avirulent Salmonella typhimurium. Alternatively, they were inoculated either once or twice with the heat-killed salmonella vaccine. No appreciable difference could be detected in the relative ability of these two strains of mice to produce antibodies against the lipopolysaccharide antigens of this pathogen under these four conditions.