title: Identification of contemporary plasmid virulence genes in ancestral isolates of Salmonella enteritidis and Salmonella typhimurium.
abstract: Six epidemiologically distinct ancestral strains of Salmonella enteritidis and 5 of S. typhimurium from the pre-antibiotic era were examined for plasmid content, and for presence of plasmid genes implicated in mouse-virulence. Five sizes of plasmid were detected in S. enteritidis varying from 1 to 60 MDa. Two sizes of plasmid were found in S. typhimurium, 28 and 60 MDa. Plasmids of the same size were not common to both serovars. The HindIII restriction patterns of 3 of the ancestral S. enteritidis plasmids were identical to the modern 38 MDa plasmid, while all contained identical bands of 3.5, 2.7 and 1.9 kb. All the 60-MDa S. typhimurium plasmids, ancestral and contemporary, had an identical restriction pattern. Three different sized S. enteritidis plasmids and one size S. typhimurium plasmid contained a 3.5-kb DNA fragment carrying the virulence locus VirA. The VirB virulence locus was located on a 2.7-kb DNA fragment in S. enteritidis and on a 2.5-kb fragment in S. typhimurium. Both loci were precisely conserved between the ancestral strains and the modern representatives of both serovars.
authors.affiliation: Plasmid Genetics Unit, National Collection of Type Cultures, Central Public Health Laboratory, London, U.K.
authors.forename: C S
authors.initials: CS
authors.lastname: Jones
authors.forename: D J
authors.initials: DJ
authors.lastname: Osborne
mesh_terms: D016172:DNA Fingerprinting; D005798:Genes, Bacterial; D010957:Plasmids; D012477:Salmonella enteritidis / Q000235:genetics / Q000472:pathogenicity*; D012486:Salmonella typhimurium / Q000235:genetics / Q000472:pathogenicity*; D012689:Sequence Homology, Nucleic Acid; D014774:Virulence