Theoretical fragment length (bp) Actual fragment length (bp) of O157:H7 Actual fragment length (bp) of K-12 Restriction enzyme Hha I Hae III Hha I Hae III Hha I Hae III Escherichia coli with 41 F – 1066R primer set 508 317 491 331 496 306 359 204 372 217 366 184 197 167 205 167 203 159   161   166   155   156   160   146   34   nd*   nd   25   nd   nd *because they were smaller than the lower limit of detection

Table 3: Theoretical and actual fragment length of PCR products amplified with the 41F-1066R primer set and digested with HhaI and HaeIII in E. coli.