Passive protection against heterologous gram-negative bacteria mediated by antiserum to epimeraseless Rc mutant of Salmonella minnesota.

Antiserum to the epimeraseless Rc mutant of Salmonella minnesota was prepared by immunization of rabbits. The antiserum provided good protection in mice i.p. challenged with 125 and 25 LD50 doses of live heterologous Gram-negative bacteria i. e. S. typhimurium, Escherichia coli and Pseudomonas aeruginosa. The protection against Klebsiella pneumoniae was negligible. Pre-immune rabbit serum produced only marginal protection. The protective effect of S. minnesota Rc antibodies was entirely abolished upon absorption of Rc antiserum with homologous bacteria. Pre-immune and absorbed sera exhibited a similar protective effect at lower LD50 values, namely 5 and 1 LD50.