Plasmid profile analysis and restriction enzyme fingerprinting of Salmonella DO-group strains

In Sweden Salmonella dublin is the most common serotype within the DO-group isolated from animals. In recent years also salmonella strains belonging to the DO-group but lacking H-antigen have been isolated from cattle in different areas. It was not possible to further differentiate the latter strains by serological methods. However, all Salmonella dublin strains and those strains lacking H-antigen carried a 50 Mdal plasmid exhibiting the same EcoRI and Hind III restriction enzyme digestion pattern. Two of the 26 strains contained an additional 5 Mdal plasmid. Other serotypes within the DO-group investigated, namely Salmonella enteritidis and Salmonella panama, carried plasmids smaller than 50 Mdal. The plasmid profiles and restriction enzyme digestion patterns indicated that the salmonella strains lacking H-antigen were variants of Salmonella dublin. Thus, analysis of plasmid profile and restriction enzyme fingerprinting are useful complements to serological methods in the differentiation of salmonella DO-group strains.