The occurrence of atypical enteropathogenic Escherichia coli strains among children with diarrhea in Iran.

The aim of this study was to investigate the genetic diversity and class 2 integron content of typical and atypical enteropathogenic Escherichia coli (EPEC) strains isolated from children less than 5 years of age. Biochemical tests and serogrouping were performed for identification of isolated strains, and each isolate was tested for susceptibility to 7 antimicrobial agents. The identity of EPEC and their class 2 integron content was confirmed by PCR analysis and sequencing. Subtyping of Escherichia coli spp. was performed through pulsed-field gel electrophoresis (PFGE) analysis. All EPEC strains were resistant to 6 antimicrobial agents except for gentamycin. The most prevalent serogroups among EPEC strains were found to be members of O86 and O127 serogroups (37.7 %) and O44, O125, and O128 (42.8 %). The majority of our EPEC isolates (60.7 %) were identified as atypical. Among the total 28 isolates, 4 (14.2 %) harbored a class 2 integron 1,500 or 2,300 bp in size, corresponding to dfrA1-sat1 and dfrA1-sat1-aadA1 resistance gene cassette arrays, respectively. PFGE analysis showed an extensive diversity among the isolates. No PFGE clustering was observed according to bundle-forming pilus (bfp) bacteria, suggesting that PFGE analysis could not discriminate between typical and atypical EPEC strains. The high ratio of antibiotic-resistant strains and the large heterogeneity among EPEC isolates with low prevalence of class 2 integrons signify the need to examine for other mechanism(s) involved in conferring resistance in typical and atypical populations of EPEC.