[Effect of conjugative R plasmids on the virulence of antibiotic-sensitive Salmonella strains and their streptomycin-resistant mutants].

The pathogenicity level of antibiotic sensitive and streptomycin resistant strains of S. typhimurium, S. paratyphi B and S.

[Conjugated plasmids of antibiotic resistance in conditionally pathogenic enterobacteria in infants with salmonellosis].

Sensitivity to 10 antibiotics of 1074 strains of opportunistic enterobacteria isolated from 117 children at the age of 2 years was studied (57 healthy children and 60 children with salmonellosis). The structure of the conjugative drug resistance of the opportunistic enterobacteria, the frequency of their isolation and the spectrum correlating with multiple resistance of the strains to 4-10 antibiotics were shown. The frequency of the conjugative determinants of the antibiotics resistance in the opportunistic bacteria isolated from the patients with salmonellosis was higher.

[Structure of salmonellal transmissive resistance to antibiotics].

The structure of transmissive resistance to antibiotics was studied in 1260 Salmonella strains of 57 serotypes and R-plasmid resistance was found in the representatives of 13 (31.6 per cent) serotypes. The transmissive resistance correlated with multiple resistance to 4--10 antibiotics.

[Transmissive drug resistance and virulence of "epidemic" strains of S. typhimurium].

A total of 59 "epidemic" strains of S. typhimurium and 52 cultures isolated from the cases with sporadic diseases were studied with respect to the nature of their resistance to 10 antibiotics and virulence for albino mice under conditions of subcutaneous and oral inoculation. The virulence of the cultures isolated from the cases with sporadic diseases was higher in the strains sensitive to antibiotics.