[Live enteric typhoid vaccine consisting of a Vi-negative double-dependent mutant of S. typhi and a Vi-positive strain of Citrobacter].

The authors present experimental data on the study of the living enteral vaccine against the typhoid infection from the Vi-negative strain of salmonella with a double-dependence by streptomycin and purine, and from the Vi-positive strain -- citrobacter 5396/38. The method of immunoelectrophoretic analysis showed an indenticity of the O- and H-antigens of the doubledependent mutant with the O- and H-antigens of the typhoid strains of bacteria (Ty2-4446 and 5501). A sufficiently marked immunological reaction was revealed in the tests of antibody formation and in the study of the preventive activity of the sera of the immunized rabbits. The efficacy of the enteral immunization with the associated vaccine consisting of a doubledependent mutant of typhoid bacilli and the citrobacter strain in the doses tested (a 6-fold immunization) was demonstrated in experiments on albino mice. Association in one preparation of the cultures under study did not lead to any changes in the immunogenic properties of these strains. The cells of the mutant strain administered per os gave a positive culture (from the mouse organism) only in the course of the first 24 hours, in difference from the citrobacter strain which gave a positive culture in the course of 14 days.