Investigation of the occurrence of siderophore genes in E. coli isolated from foodborne and clinical samples and identification of genotypic relationship of Escherichia coli by using PFGE method

Iron is essential for Escherichia coli growth and survival in the host and the external environment, but its availability is generally low due to the poor solubility of its ferric form in aqueous environments and the presence of iron-withholding proteins in the host. Most E. coli can increase access to iron by excreting siderophores such as enterobactin, which have a very strong affinity for Fe3+. A smaller proportion of isolates can generate up to 3 additional siderophores linked with pathogenesis; aerobactin, salmochelin, and yersiniabactin. This study compared the presence of siderophore genes in E.coli strains isolated from clinical and food samples, and studied genotypic relationship of Escherichia coli strains. Sixty five of E. coli strains were isolated from the clinical samples and 35 of E.coli isolated from the food samples were our material in this study. The prevalence of the siderophore-related genes were determined in the E.coli strains by the PCR method which was as follow: enterobactin receptor (Fep A), 18%; enterobactin biosynthesis (Ent A), 18 % ; yersiniabactin receptor (Fyu A), 17%; heme receptor (Chu A) 16%; aerobactin receptor (iut A),12%; aerobactin biosynthesis (iuc A),15%; and salmochelin receptor (iro N), 3%, and iron-responsive element (ire A), 1 %. The genotypic relationship of E.coli strains have also studied by using PFGE method and the evaluation of PFGE analysis showed that 6 (6.8%) out of 89 isolates of human and foodborne isolates had a clonal relationship while there was no significant relationship between the other isolates. Conclusion: The siderophore-related genes are main factors in the growth and survival of the E.coli clinical strains and their adaptation to the iron limiting environment, our results supported that and found that siderophore genes are higher prevalence in E.coli isolated from clinical samples than food samples.