[Effect of conjugative R plasmids on the virulence of antibiotic-sensitive Salmonella strains and their streptomycin-resistant mutants]. / Vliianie kon"iugativnykh R-plazmid na virulentnost' chuvstvitel'nykh k antibiotikam shatmmov sal'monell i ikh streptomitsinorezistentnykh mutantov.

The pathogenicity level of antibiotic sensitive and streptomycin resistant strains of S. typhimurium, S. paratyphi B and S. kottbus changed under the effect of identical R plasmids more frequently in contrary directions. The conjugative plasmids of antibiotic resistance widened the ranges of the virulence changes in the Salmonella serovars for albino mice. It was found that 7 out of 8 plasmids studied significantly decreased and increased the virulence of the antibiotic sensitive Salmonella strains. As a rule, R plasmids of various origin decreased the virulence of all the tested streptomycin chromosome resistant causative agents of salmonellosis.

[Conjugated plasmids of antibiotic resistance in conditionally pathogenic enterobacteria in infants with salmonellosis]. / Kon"iugativnye plazmidy antibiotikorezistentnosti uslovnopatogennykh énterobakterii u detei pri sal'monelleze.

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. The structure of the conjugative drug resistance of the opportunistic enterobacteria in the dynamics of the salmonellosis process was close to the transmissive R-plasmid resistance of S. typhimurium.

[Structure of salmonellal transmissive resistance to antibiotics]. / Struktura transmissivnoi ustoichivosti sal'monell k antibiotikam.

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. The rate of occurrence of the transmissive R-plasmids was markedly higher in the bipathogenic serotypes. The structure of the R-plasmid resistance was most pronounced and diverse in S. typhimurium. It was usually revealed simultaneously with registration of the hospital infection. The plasmid with the determinants of resistance to erythromycin and benzylpenicillin was found only in this serotype. The nature of resistance and spectrum of transmissive resistance to antibiotics in Salmonella may serve as an additional epidemiological feature of the strains.

[Transmissive drug resistance and virulence of "epidemic" strains of S. typhimurium]. / Transmissivnaia lekarstvennaia ustoichivost' i virulentnost' "épidemicheskikh" shtammov 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. The "epidemic" strains were characterized by the lowest virulence for the mice and resistance to 8-10 antibiotics simultaneously with the transmissive nature of resistance to 1-5 drugs. The transmissive nature of resistance to antibiotics and its spectrum may serve an additional epidemiological marker of the strains.