Effect of Corynebacterium parvum treatment on the growth of Salmonella enteritidis in mice.

The growth of Salmonella enteritidis in mice pretreated with 700 mug of killed Corynebacterium parvum was less than that seen in normal CD-1 mice. In treated mice, there was an early increased inactivation of the blood, liver, and spleen bacterial populations, followed by a prolonged period of slow but continuous bacterial growth. The treated mice failed to develop significant delayed hypersensitivity and did not show the characteristic antibacterial immune response seen in untreated infected animals. Eventually sufficient resistance did develop in most of the treated animals to protect them against the lethal effects of the challenge infection. The peak C. parvum effect was seen when S. enteritidis was injected 7 to 14 days later. Injection of C. parvum 24 h after the bacterial challenge actually potentiated the Salmonella infection. There was no evidence of an increased specific humoral response by the C. parvum-treated mice, suggesting that the slower growth of the S. enteritidis was due to the continued enhanced killing of the bacterial population by the nonspecifically stimulated cells of the reticuloendothelial system, rather than to any specific augmentation of the host immune response.