Effects of Repeated Subculturing and Prolonged Storage at Room Temperature of Enterohemorrhagic Escherichia coli O157:H7 on Pulsed-Field Gel Electrophoresis Profiles

Three clinical strains of enterohemorrhagic Escherichia coli O157:H7 which were subcultured repeatedly or stored at room temperature over a 25-week period showed appreciable variations in their pulsed-field gel electrophoresis fragment patterns. The variations could be explained by a couple of spontaneous genetic events at most and thus did not invalidate the genetic lineage of the strains.