title: Prevalence and molecular epidemiology of antibiotic-resistant Salmonella typhimurium and Salmonella dublin in Danish cattle.
abstract: Among 130 strains of S. typhimurium and 191 strains of S. dublin, all from cattle, 80% and 63%, respectively, were resistant to one, two or three antibiotics. Mono-resistance to sulphonamides was most common. Plasmid load was analysed by conjugation, transformation, extraction of plasmid DNA and subsequent electrophoresis in agarose gels. Plasmid DNA from 38 strains was further analysed by restriction with endonuclease EcoR1. On the basis of this, the strains were classified into four groups. Two groups held S. typhimurium, one held S. dublin and one group held both serotypes. This suggests that dissemination of strains and plasmids mainly occurs through clonal spread of strains. However, plasmid transfer per se also takes place, as exemplified by the fact that indistinguishable plasmids were found in two different serotypes. Strains of one group had contaminated a water-course. Strains of this group were furthermore isolated from humans in the same area as the infected cattle. Strains of this group had an R pattern and a phage-type similar to the R pattern and phage-type of the early isolates of a strain that became epidemic in British cattle. It is discussed whether Denmark, which was previously almost free of cattle salmonellosis, is experiencing the first warnings of an epidemic similar to the one in the UK.
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial / Q000235:genetics; D003718:Denmark; D004352:Drug Resistance, Microbial; D010957:Plasmids; D012475:Salmonella / Q000187:drug effects* / Q000235:genetics; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000187:drug effects*
chemical_list: D004269:DNA, Bacterial; D004262:DNA Restriction Enzymes