Each 50 µl, multiplex - PCR reaction mixture contained the concentration of four primer pairs stx1: stx2: eae: ehxA with ratio 1: 1: 1: 2 (0, 4: 0, 4: 0, 4: 0, 8mM respectively), MgCl2 concentration is 3mM, Taq polymerase 5 µl (5u / µl), enough 50 µl RNase-free water under the following conditions.