Uropathogenc Escherichia coli (UPEC) CFT073 has a pathogenicity-associated island (PAICFT073), which causes pyelonephritis and cystitis. Using PCR method, we found the prrA gene of PAICFT073 in E. coli O157:H7 EDL933. Further detailed PCR screening of 38 open reading frames, the right and left junction sequences of PAICFT073, revealed that it is the prrA-modD-yc73-fepC gene cluster but not the PAICFT073 present in E. coli O157:H7 EDL933. A rapid preliminary analysis suggested that the prrA-modD-yc73-fepC gene cluster of the PAICFT073, is present in 43 strains of E. coli O157:H7 containing Shiga toxin (Stx) gene but absent in 19 strains of E. coli O157:H7 without Stx gene. A strict co-occurrence of the prrA-modD-yc73-fepC gene cluster and Stx genes was observed, regardless of their origin. The prrA-modD-yc73-fepC gene cluster encode proteins probably involved in iron uptake system, which strongly suggests the importance of iron metabolism in the Stx-mediated virulence. In addition, the prrA-modD-yc73-fepC gene cluster may be used as a diagnostic marker to distinguish E. coli O157:H7 strains containing Stx gene from that without Stx gene, and possibly to quickly detect other pathogenic gram-negative bacteria containing the Stx gene.