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Volume 44, Number 1, February 2011

Molecular and phenotypic characterization of atypical enteropathogenic Escherichia coli serotypes isolated from children with and without diarrhea

Mohammad Mehdi Aslani, Mohammad Yousef Alikhani

Received: August 12, 2009    Revised: October 16, 2009    Accepted: November 30, 2009   


Corresponding author:

M.Y. Alikhani

Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.
E-mail address:


Background and purpose: 

We characterized 36 atypical enteropathogenic Escherichia coli (EPEC) serotypes isolated from children with and without diarrhea in Iran. Because the identification of atypical EPEC based on biochemical features is rather difficult and time consuming, we used a combination of three approaches, including a polymerase chain reaction-based method, culture adherence assay, and the restriction analysis of fliC gene (fliC-restriction fragment length polymorphism), to identify E coli serotypes.



To distinguish typical and atypical EPEC strains, the presence of EPEC attaching effacing A gene (eaeA) gene and EPEC-attaching factor (EAF) plasmid were analyzed. All E coli strains were identified based on the detection of the eaeAþ, bundle-forming pili A gene (bfpA ), EAF  or eaeA , bfpAþ, EAF  profiles and the absence of stx (encoded for shiga toxin) gene as atypical EPEC



All strains studied belonged to 5 atypical EPEC serogroups and 15 serotypes based on the virulence profiles. Of 36 atypical EPEC serotypes, 22 (61.2%) and 14 (38.8%) strains isolated from diarrheal and healthy cases, respectively. O142:H48 (19.5%) and O111:H21 (11.1%) serotypes were the most prevalent isolates, followed by serotypes O111: H  and O86:H48 (5.6% each).



The characteristics of the atypical EPEC serotypes from children with diarrhea were significantly different from those without diarrhea. The compilation of data on atypical EPEC strains presented here indicates the importance of a combined approach of conventional and molecular tests to study the virulence and epidemiology of EPEC serotypes in human subjects.


Key words:

Atypical EPEC; Diarrhea; Escherichia coli; Pathogenicity; Virulence gene