Immunogenicity of Clostridium septicum in guinea pigs.

Five strains of Clostridium septicum were used to prepare bacterins, bacterin-toxoids, toxoid, and combinations of bacterins or bacterin-toxoids. These preparations were tested for immunogenicity in guinea pigs vaccinated subcutaneously with 1.0 ml of product. Usually, a second vaccination was given 21 to 24 days later. The immunity of groups of vaccinated guinea pigs was challenged with as many as 22 strains of C septicum. When challenge exposed with homologous strains at 21 to 24 days after one vaccination or 10 t0 18 days after a second vaccination, 60% to 100% of the guinea pigs in each group survived. Demonstrable cross-protection among strains of C septicum varied from none to 100% protection in vaccinated guinea pigs. A combination of bacterin-toxoid prepared from four selected strains protected 70% to 100% of the vaccinated guinea pigs challenge exposed with 21 strains. Duration-of-immunity studies demonstrated a twofold to fourfold decrease in protection when the vaccination-to-challenge interval was extended an additional 3 weeks. Strains of C septicum do not have an effective common immunogen and the stimulated immunity appears to be of short duration. Antitoxin was demonstrated to be less important than other factors in protecting against C septicum infection.