Prevalence of iron transport gene on pathogenicity-associated island of uropathogenic Escherichia coli in E. coli O157:H7 containing Shiga toxin gene

Abstract

Uropathogenc Escherichia coli (UPEC) CFT073 has a pathogenicity-associated island (PAI(CFT073)), which causes pyelonephritis and cystitis. Using PCR method, we found the prrA gene of PAI(CFT073) in E. coli O157:H7 EDL933. Further detailed PCR screening of 38 open reading frames, the right and left junction sequences of PAI(CFT073), revealed that it is the prrA-modD-yc73-fepC gene cluster but not the PAI(CFT073) present in E. coli O157:H7 EDL933. A rapid preliminary analysis suggested that the prrA-modD-yc73-fepC gene cluster of the PAI(CFT073), 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.

FIG. 1

Southern hybridization profile of the EcoRI-digested chromosomal DNA with prrA and modD probes. Lanes: M, molecular standard (DNA digested with HindIII); 1, E. coli CFT073 (positive control); 2, E. coli O157:H7 EDL933; 3, E. coli O157:H7 223; 4, E. coli O157:H7 143; 5, E. coli O157:H7 PC02 (animal isolate without Stx gene); 6, E. coli HB101 (negative control). (A) Hybridization with prrA probe. (B) Hybridization with modD probe.