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A collection of 31 epidemiologically unrelated Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) isolates obtained during a 12-year period was characterised by different molecular typing methods. Plasmid profile analysis, the detection of plasmid-encoded virulence genes and ribotyping allowed little or no further differentiation amongst these isolates. Two different hybridisation patterns were observed by IS200-typing of the S. Enteritidis isolates. However, pulsed-field gel electrophoretic separation of restriction endonuclease-digested whole-cell DNA provided a high level of discrimination amongst the 31 S. Enteritidis isolates. This could be increased by the comparative use of the three suitable restriction endonucleases XbaI, SpeI and NotI. Thus, pulsed-field gel electrophoresis proved to be superior in its discriminatory value to other molecular methods such as plasmid analysis, ribotyping or IS200-typing and represents a most helpful tool for the epidemiological typing of S. Enteritidis isolates.

Salmonella enterica subsp. enterica serovar Typhimurium (Salm. Typhimurium) live vaccine strain Zoosaloral H was characterized by pulsed-field gel electrophoresis (PFGE). Each of the two suitable restriction enzymes, XbaI and SpeI, produced a unique restriction fragment pattern for this live vaccine strain which was not shared by field isolates of the same serovar. The characteristic fragment pattern proved to be stable during a 22 month observation period and was also not altered after animal passage of the vaccine strains. Thus PFGE analysis proved to be a helpful tool in the identification of Salm. Typhimurium live vaccine strain Zoosaloral H and its differentiation from wild-type isolates of the same serovar.