[R-factor distribution and characteristics of the E. coli isolated from pigs]

Studied was the occurrence of the R-factors in Escherichia coli isolated from pigs. It was demonstrated that in 73.3 per cent of the cases drug resistance could be transmitted to Citrobacter. In this instance an occasional drop-out of the markers of resistance to kanamycin, neomycin, ampicillin, tetracycline, and chloramphenicol was observed. In the author's experiments no transmission of the marker of resistance to furazolidon was established. The transmission of the signs of resistance to kanamycin and niomycin as well as to erythromycin and oleandomycin occurred always simultaneously. The possibility of transmitting the drug resistance markers of Escherichia coli to Salmonella typhimurium LT-2 made it reasonable to believe that this is one of the routes for spreading the R-factors among Salmonella organisms. No essential differences were observed between the minimal inhibitory concentration of the donor strains and the level of the acquired resistance with the recombinations. The transmission frequence of the resistance markers proved comparatively high, and ranged from 0.6.10(-3) up to 3.10(-4).