STUDIES ON PATHOGENIC HALOPHILES

IV. PATHOGENICITY TO EXPERIMENTAL ANIMALS

Abstract

From this experiment it became evident that strain N4 inoculated into mice and guinea pigs intraperitoneally caused death of the animals by bacteraemia, but strain EB102 did not. Fujino et al.⁽³⁾ reported that 0.01 mg of EB102 caused the death of mice within 12 hours after intraperitoneal inoculation. The difference between our result and Fujino's would be attributed to the decrease in pathogenicity of the strain caused by successive transfers. The heated suspension (100°C, 30 minutes) or the Seitz-sterilized broth culture of strain N4 had no fatal effect on mice after intraperitoneal injection. Takikawa⁽²⁾ observed that cats administered per or with the heated suspension of strain N4 showed fever and leucocytosis, but he could not prove exotoxin.
Although strain N4 showed almost similar growth pattern on every agar slant examined, it was observed that the organism grown on synthetic nutrient agar was less toxic than those cultivated on medium which were enriched with peptone or meat infusion. According to Ogasawara et al.^{(4, 5)} Salmonella enteritidis maintained on a synthetic medium containing no vitamin had antigenicity to produce the infection-preventing antibody in immunized animals but had no communicability (a factor of pathogenicity). Communicability was recovered by culturing the organism on a synthetic medium containing vitamin B group. Although an experiment using organisms maintained on the synthetic medium was not performed, a result similar to Ogasawara's was observed in this study. The fact that mice were not killed with intraperitoneal inoculation of normal meat infusion broth culture of strain N4 might be due to their poor multiplication in this medium. However, the effect of sodium chloride may be expected.
From this experiment it may be suggested that the injection of viable cells of strain N4 gives an incomplete immunization to prevent the infection of the organism, but injection of EB102 cells does not provide the immunity. However, a definite conclusion can not be drawn because the extended survival period was short.