MOLECULAR ANALYSIS OF SALMONELLA-ENTERICA SEROTYPE DUBLIN - BUILDING BRIDGES BETWEEN POPULATION GENETIC AND MOLECULAR EPIDEMIOLOGIC STUDIES

Population genetic studies of Salmonella enterica serotype Dublin usin g multilocus enzyme electrophoresis have recognised two dominant clone s termed Du1 and Du3. The characterisation of plasmids in Dublin sugge sts greater strain diversity. The application of restriction enzyme fr agmentation pattern (REFP) analysis of genomic DNA using Sau3A and Hin cII together with plasmid subtractive analysis can resolve anomalies i n earlier comparisons. Twenty-six isolates were selected for inclusion in the study. All had been previously characterised with respect to t heir plasmids, and were isolated from the USA, Canada and five Europea n countries. On the basis of plasmid profiles, 17 were predicted to co rrespond with Du1 and Du3. Sau3A digestion generated two distinct REFP s (A and B) of < 70% similarity, which corresponded with Du1 and Du3. After the contribution of plasmid-derived bands was subtracted, two va riants of A (A1 and A2) and four of B (B1, B2, B3 and B4) were recogni sed. Seventeen were concordant with predictions from population geneti c studies. Nine that could not be predicted on the basis of atypical p lasmid profiles all showed REFP A1 (Dull and were consistent with the incursion of additional plasmids or plasmid cointegration. REFPs from HincII digests generally corroborated Sau3A data but showed greater ov erall similarity between the strains and more influence from plasmid D NA.