Experimental salmonellosis. VII. Comparison of the immunizing effect of live vaccine and materials extracted from Salmonella enteritidis.

Kawakami, Masaya (Gunma University, Maebashi, Japan), Nobutaka Osawa, and Susumu Mitsuhashi. Experimental salmonellosis. VII. Comparison of the immunizing effect of live vaccine and materials extracted from Salmonella enteritidis. J. Bacteriol. 92:1585-1589. 1966.-Attempts were made to isolate the factors of live vaccine which immunize against Salmonella enteritidis infection in mice. Some effective substances were found in cellular extracts of this organism when those extracts were prepared by mild procedures. One of these substances was a heat-labile toxin (toxin L), which was found in an earlier study to be homogeneous as evidenced by chromatographic, ultracentrifugal, and serological analyses and which was phospholipoprotein in nature. Mice immunized with "toxin L" were protected against a 10 MLD challenge infection with a virulent strain to the same extent as animals immunized with live vaccine of an attenuated strain, SER. However, no agglutinin could be detected in sera of the animals given "toxin L." Another effective substance, endotoxin, a heat-stable toxin, which was extracted from the same organisms, demonstrated poor protective effect. Possible mechanisms of immunization with live vaccine in S. enteritidis infection in mice are discussed.