PFGE analysis of serotype Typhimurium strains representing different clones. Lanes: L, PFGE ladder (New England Biolabs, Schwalbach, Germany); 1 through 4, XbaI PFGE profiles generated by serotype Typhimurium LT2 (PFGE1), LSP14/92 (PFGE3), LSP31/93 (PFGE4), and ATCC 14028 (PFGE2), respectively. Molecular sizes indicated in the figure correspond to the LT2 XbaI fragment sizes given in reference 12. The nine clinical isolates under study generated PFGE4. The arrow indicates the fragment corresponding to the 90-kb virulence plasmid.