Enhanced resistance of mice to Escherichia coli infection induced by administration of peptidoglycan derived from Bifidobacterium thermophilum.

Peptidoglycan (PG) of Bifidobacterium thermophilum (B. thermophilum) from swine were orally administered to SPF-ICR mice in order to confirm the enhancement of the defence activity of the mice against Escherichia coli (E. coli) infection. It was found that the survival rates of the PG-administered group were significantly higher than those of the non-treated control group after the single oral administration of PG. And the proper concentration at which PG enhanced defence activity most effectively was found to be 500 micrograms per mouse. The number of E. coli in the peripheral blood, liver and spleen of the PG-administered group at 24 hr after the inoculation was significantly smaller than that in the control group. Liver weight per body weight in the PG treated group significantly increased in comparison with that of the non-treated group. The number of blastoid plasmacytes in the spleen of the PG-administered mice was found to be greater than that in the control group. These results indicate that the defence activity of mice against E. coli infection was accelerated by PG treatment.