[Protective effects of bacterial immunostimulants in mice infected by "Klebsiella pneumoniae" resistant to antibiotics after mutation or by plasmid transfer].

A streptomycin-resistant strain of K. pneumoniae obtained after mutation in vitro was found to be less virulent than the sensitive strain in mice. However, a single injection of lipopolysaccharides (LPS) administered 24 hours before challenge increased the host's resistance to both strains. In contrast, the virulence was not changed in K. pneumoniae accepting R-factors for ampicillin, streptomycin, chloramphenicol, tetracycline and sulphonamide. The plasmids were transferred to K. pneumoniae from two strains of Escherichia coli possessing different R-factors with the same resistance pattern. As in the first case, mice pretreated by endotoxin were protected against a challenge by microorganisms carrying R-factors. The capacity of the stimulated host to destory resistant or sensitive organisms was of the same order. Klebsiella recovered 5 or 24 hours after infection from the blood, liver and spleen did not lost their antibiotic-resistance. In this study, BCG and Corynebacterium granulosum were also used. Like LPS, these two immunostimulants protected very effectively mice infected with K. pneumoniae rendered resistant to antibiotics by R-factor transfer.