Molecular analysis of Salmonella enterica serotype Dublin: Building bridges between population genetic and molecular epidemiological studies

Abstract

Population genetic studies of Salmonella enterica serotype Dublin using multilocus enzyme electrophoresis have recognised two dominant clones termed Du1 and Du3. The characterisation of plasmids in Dublin suggests greater strain diversity. The application of restriction enzyme fragmentation pattern (REFP) analysis of genomic DNA using Sau3A and HincII together with plasmid subtractive analysis can resolve anomalies in earlier comparisons. Twenty-six isolates were selected for inclusion in the study. All had been previously characterised with respect to their plasmids, and were isolated from the USA, Canada and five European countries. On the basis of plasmid profiles, 17 were predicted to correspond with Du1 and Du3. Sau3A digestion generated two distinct REFPs (A and B) of < 70% similarity, which corresponded with Du1 and Du3. After the contribution of plasmid-derived bands was subtracted, two variants of A (A1 and A2) and four of B (B1, B2, B3 and B4) were recognised. Seventeen were concordant with predictions from population genetic studies. Nine that could not be predicted on the basis of atypical plasmid profiles all showed REFP A1 (Du1) and were consistent with the incursion of additional plasmids or plasmid cointegration. REFPs from HincII digests generally corroborated Sau3A data but showed greater overall similarity between the strains and more influence from plasmid DNA.

Host adapted serotypes of Salmonella enterica

“…Dublin strains showed the same RFLP-patterns when hybridized with the insertion sequence IS200 while restriction polymorphism can be demonstrated by ribotyping [41]. The clonal nature of Dublin has been confirmed by analysis of molecular variation in the serotype specific plasmid of this host-adapted serotype [42] and also showed that the geographically restricted clone (Du3) harboured a serotype specific plasmid more closely related to that of the UR serotypes. This has been further corroborated by incompatibility studies of the plasmids in both Du3 and the widespread clone Du1 (D. J. Platt, unpublished).…”

Isolation and characterization of coliforms from glacial ice and water in Canada's High Arctic

“…Whole-cell DNA was extracted as described by Platt et al (1996). Briefly, cultures were grown overnight in lOml of Brain Heart Infusion broth (BHI) (Oxoid), centrifuged at 4000 rev min-' for 5 min and resuspended in 3 x 1 ml volumes of TE50 buffer (Tris 10 mmol 1-', EDTA 50 mmol l-', pH 8.0).…”

Investigation of the genetic diversity among isolates of Salmonella enterica serovar Dublin from animals and humans from England, Wales and Ireland

“…Salmonellae are not directly comparable to other pathogenic species with regards to diversity of strains, because they have undergone at least two levels of species subdivision, firstly to subspecies enterica and secondly to serotype, so that the expected diversity within individual serotypes is often low (Platt et al . 1996).…”

“…Salmonellae are not directly comparable to other pathogenic species with regards to diversity of strains, because they have undergone at least two levels of species subdivision, firstly to subspecies enterica and secondly to serotype, so that the expected diversity within individual serotypes is often low (Platt et al 1996). However, a wide range of genotypic techniques has been developed in recent years and has provided invaluable tools to study the diversity of the populations within some of these groups (Liebana et al 2001b).…”