title: Importance of the serovar-specific plasmid for virulence of salmonella strains in calves.
abstract: To evaluate the influence of serovar-specific plasmids on salmonella virulence in calves, experiments were performed involving infection, by the oral route, with mixtures of strains containing equal counts of a plasmid-carrying and a plasmid-free strain of the same serovar. The concentration ratio between the plasmid-carrying and the plasmid-free strain which had developed in the organs of the infected animals was used for a comparative evaluation of virulence and pathogenetic behaviour of the strains. While in the S. typhimurium strains studied, the presence of the plasmid was accompanied by a significantly increased colonization and multiplication of the agent in the host's body, examination of S. enteritidis and S. dublin revealed that the plasmid-free strains exhibited identical or even significantly higher bacterial counts than the plasmid-carrying strains in organs. The fact that plasmid-free salmonella strains with a high virulence for calves have been found demonstrates that the presence of a serovar-specific plasmid is not an indispensable requirement for the development of salmonellosis in calves.
authors.affiliation: Federal Institute for Health Protection of Consumers and Veterinary Medicine, Jena, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Steinbach
authors.forename: R
authors.initials: R
authors.lastname: Helmuth
authors.forename: H
authors.initials: H
authors.lastname: Koch
authors.forename: U
authors.initials: U
authors.lastname: Methner
authors.forename: H
authors.initials: H
authors.lastname: Meyer
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D007413:Intestinal Mucosa / Q000382:microbiology; D007583:Jejunum / Q000382:microbiology; D008198:Lymph Nodes / Q000382:microbiology; D010957:Plasmids / Q000235:genetics*; D012475:Salmonella / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D012481:Salmonella Infections, Animal / Q000235:genetics*; D012477:Salmonella enteritidis / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity; D012486:Salmonella typhimurium / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity; D013154:Spleen / Q000382:microbiology; D014774:Virulence / Q000235:genetics*