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

Abstract

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 5years 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 2,300bp 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.