Evaluation of molecular typing methods for Salmonella enterica serovar Typhimurium DT104 isolated in Germany from healthy pigs

The discriminatory power of four different DNA based typing methods was tes ted for the molecular subtyping of Salmonella Typhimurium phage type DT104 isolates. German DT104 strains (n = 133) originating from slaughter pigs we re analysed by plasmid profiling, and 32 of them by pulsed-field gel electr ophoresis (PFGE) using the restriction enzymes XbaI, SpeI or BlnI, random a mplification of polymorphic DNA (RAPD) using 13 different primers and IS200 typing. A resulting subtyping scheme was obtained which is based on the mo st discriminatory power of the individual methods i.e. plasmid profiling an d PFGE with all three enzymes. The index of discrimination obtained by the subtyping scheme was 0.909 closely approaching the maximum value of one. Al though minor differences occurred in the molecular DNA pattern of single DT 104 strains, a dominating subtyping pattern was observed confirming other s tudies which showed, that S. Typhimurium DT104 isolates are highly clonal.