Molecular characterization of Salmonella enterica subsp. enterica serovar Typhimurium DT1 isolates

SUMMARY Salmonella Typhimurium DT1 is endemic to Finland and has caused human outbreaks since the 1960s. Domestic DT1 isolates (n=235) from 1972 to 1999 from human cases, animals and other sources, as well as foreign DT1 isolates from human cases (n=20) were analysed by molecular methods. Pulsed-field gel electrophoresis (PFGE) yielded 38 XbaI profiles. Of these, XbaI profile 10 was seen in 49 % (125/255) of the isolates. Twelve IS200 profiles were obtained ; the most common IS200 profile D was seen in 64% (33/52) of the isolates. Two clusters were formed by compilation of the XbaI–, BlnI– and SpeI–PFGE and IS200 profiles and possession of the serovar-specific virulence plasmid. The major cluster contained eight IS200 profiles, including IS200 profile D and XbaI profile 10, and had no virulence plasmid, and can be regarded as typical of the endemic Typhimurium DT1 infection.