Infectivity and Antigenicity of Streptomycin-Dependent Salmonella typhosa

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Abstract
A streptomycin-dependent mutant of S. typhosa exhibited a requirement for streptomycin in vivo. Virulence was manifested by fatal infections in streptomycin-treated mice and was probably due to accumulation of the endotoxin that the bacilli contained. Injection of dependent bacilli does not appear to initiate the carrier state in untreated mice, but large numbers of bacilli are still present in the tissues of treated mice 14 days later. Immunogenicity of the dependent mutant 27 V administered as a live vaccine was demonstrated by appearance of 0 agglutinins in the serum of rabbits. No loss in anti-genicity was demonstrated in the dependent mutant as shown by the results of reciprocal absorption tests with the streptomycin-sensitive parent strain and tests with monospecific testing fluids. Stability of the mutant was exhibited by failure to obtain reversion in vivo or in vitro. The dependent strain consists of a homogeneous population with respect to streptomycin requirement.