PFGE fingerprint patterns of S. suis isolates used in the present study using the ApaI endonuclease. Lanes 1 to 6, fluoroquinolone-susceptible strains; lanes 7 to 17, fluoroquinolone-resistant isolates. The first and last lanes are bacteriophage lambda ladder PFGE markers (Boehringer Mannheim, Germany); lane 1, S. suis ATCC 43765; lane 2, BB1001; lane 3, BB1002; lane 4, BB1003; lane 5, BB1004; lane 6, BB1005; lane 7, BB1006; lane 8, BB1007; lane 9, BB1008; lane 10, BB1009; lane 11, BB1011; lane 12, BB1012; lane 13, BB1013; lane 14, BB1014; lane 15, BB1015; lane 16, BB1016; lane 17, BB1017. Analysis was performed with QuantityOne software (Bio-Rad, Richmond, CA).