STUDIES ON THE EXPERIMENTAL TYPHOID.

Abstract

Mice immunized with living microorganisms gain a steadfast resistance against further infection of S. enteritidis. Immunization with killed microorganisms are also effective. However, it has been presumed that immune mechanism of both vaccine should differ essentially. The resistance of mice immunized with living and killed vaccines were compared observing supressing ability of mice against infected microorganisms.Mice were immunized with living attenuated strain SER and subsequently with virulent strain116-54. Another group was immnnized with killed microorganisms (chrome alum vaccine). These two groups and non-immune controls were infected with virulent strain of S. enteritidis. For the purpose of differentitation of immune and challenge strains, a streptomycine-resistant mutant of virulent S. enteritidis was used for the challenge.In the organs of mice immunized with killed bacteria, as well as non-immune controls, gradual multiplication of challenged strain was observed. On the other hand, in the group immunized with living vaccine, the challenged bacteria in liver and spleen decreased slowly and disappared at about one month.