The effect of preadministration of Corynebacterium parvum on the protection afforded by heat-killed and acetone-killed vaccines against experimental mouse typhoid.

Mice given an intraperitoneal injection of 0.5 mg. Corynebacterium parvum (dry weight) before vaccination with heat-killed (HK) or acetone-killed (AK) Salmonella typhimurium vaccine and later challenged intraperitoneally with S. typhimurium strain 1566, showed a statistically significant increase in mortality when compared with mice that had received only C. parvum but no vaccine. They also showed a higher mortality rate than mice receiving only HK or AK vaccine or mice that had received no vaccine before challenge. Prior administration of C. parvum to mice that are vaccinated with HK or AK vaccine appears to make them more susceptible to an intraperitoneal challenge with S. typhimurium. This was more apparent with HK vaccine than with AK vaccine.