Phenotypic and Genotypic Characterization of Enteropathogenic Escherichia coli (EPEC) strains in Tehran, Iran

Enteropathogenic Escherichia coli (EPEC) strains can be detected by serogrouping and the presence of enterocyte attaching- effacing (eae) gene. Most EPEC strains belong to a certain O antigenic group. Locus of enterocyte effacement (LEE) Pathogenicity Island contains the eae gene and secretory proteins (ESPs) that introduce the attaching-effacing lesion. LEE inserted in tRNA genes include the SelC, PheU and PheV sites. The aim of the present study was to genetically characterize EPEC strains isolated from children with diarrhea.

Serogrouping was performed by EPEC antisera in 321 E. coli isolates. The presence of eae, stx, espB, and eaf genes and detection of insertion sites of LEE was done by PCR using specific primers.

Seventeen (5.3%) isolates belonging to 7 EPEC serogroups were identified among the whole material and all carried the eae gene. None of the 321 isolates showed presence of stx gene indicating that all 17 isolates classified as EPEC by O serogrouping did not belong to the enterohaemorrhagic E. coli (EHEC) group. Of these, 8 (53%) isolates carried the eaf and 16 (94.1%) carried the espB gene. The insertion sites of LEE in serogrouped isolates were selC (in 6 isolates), pheU (in 7 isolates) and pheV (in 2 isolates). The insertion site in 2 isolates was not determined by PCR.

Serogrouping and detection of the eae gene showed to be reliable for detection of EPEC strains. No Shigatoxin- producing E. coli (STEC) strain was found among the isolates. Detection of the insertion site of LEE showed that selC, pheU or PheV are insertion sites of LEE in the EPEC strains.