(A) PFGE profiles of chromosomal DNA of S. porcinus isolates after digestion with SmaI. Lanes 1 and 8, molecular size markers (in kilobases; lambda DNA concatemers ranging from 48.5 to 1,018.5 kb); lane 2, SS-1029; lane 3, SS-558; lane 4, SS-740; lane 5, SS-857; lane 6, SS-997; lane 7, SS-1058; lane 9, 1499-84; lane 10, 369-94; lane 11, 1013-94; lane 12, 4188-95; lane 13, 4189-95; lane 14, 663-96; and lane 15, 4524-96. (B) Dendrogram resulting from computer-assisted analysis of the PFGE profiles of S. porcinus isolates. The Dice coefficient was used for calculating the percentages of similarity among the profiles.