[Influence of plasmid pR50 controlling bacterial protease activity on Salmonella experimental infection].

The comparative analysis of the infectious process and immunological parameters in (CBA x C57BL/6)F1 mice infected with S. typhimurium isogenic strains differing by the presence of plasmid pR50 determining protease activity, was carried out. A growth in the expression level of antilactoferrin, anticomplementary and anti-immunoglobulin activity in bacteria isolated from the spleen in the course of the infectious process was detected. In mice infected with S. typhimurium having plasmid pR50, in contrast to nonplasmid recipients, a higher level of contamination of organs, the suppression of spontaneous, stimulated production of interferon-gamma and the bactericidal properties of peritoneal macrophages were noted. The data obtained in this investigation suggested that the acquisition of R-plasmid of 50 MD, controlling protease activity and multiple medicinal resistance, contributed to the persistence of intracellular bacteria.