Oral immunization of mice with killed Salmonella typhimurium vaccine.

A study was undertaken to assess the efficacy of oral, parenteral, and intraperitoneal immunization methods of administering killed Salmonella typhimurium vaccine to mice and to evaluate the effectiveness of single and multiple doses of the vaccine containing varied numbers of the killed bacteria. A further objective of this study was to evaluate the effect of adding substances to the vaccine to which have been ascribed "adjuvant" properties. The protection was estimated by isolation of bacteria from the spleen and feces after oral challenge of the mice with live S. typhimurium. The results showed that one or more doses of 10(10) organisms given orally led to significant protection. This rate of protection increased proportionately with the number of doses up to 10 doses, which offered 100% protection. Streptomycin, when added to multiple doses of 10(9) or more organisms given orally, increased the degree of protection, but beryllium sulfate and pertussis vaccine did not. Although multiple doses afforded similar systemic protection by all three routes of immunization, oral immunization yielded significantly greater local protection than that observed after subcutaneous or intraperitoneal immunization.