Phylogenetic analysis of Escherichia coli strains isolated from human samples

Document Type : Original article


1 Department of Pathobiology School of Veterinary Medicine Shiraz University Shiraz, 71345-1731 Iran

2 Department of Pathobiology School of Veterinary Medicine Shiraz University Shiraz, 71345-1731 Iran

3 Dept. of Bacteriology & Virology Shiraz Medical School Shiraz University of Medical Sciences P.O. Box 71455-119, Shiraz 71455, Iran.

4 PhD student in Department of Pathobiology School of Veterinary Medicine Shiraz University Shiraz, 71345-1731 Iran


Escherichia coli (E. coli) is a normal inhabitant of the gastrointestinal tract of vertebrates, including humans. Phylogenetic analysis has shown that E. coli is composed of four main phylogenetic groups (A, B1, B2 and D). Group A and B1 are generally associated with commensals, whereas group B2 is associated with extra-intestinal pathotypes. Most enteropathogenic isolates, however, are assigned to group D. In the present study, a total of 102 E. coli strains, isolated from human samples, were used. Phylogenetic grouping was done based on the Clermont triplex PCR method using primers targeted at three genetic markers, chuA, yjaA and TspE4.C2. Group A contained the majority of the collected isolates (69 isolates, 67.64%), followed by group B2 (18 isolates, 17.64%) and D (15 isolates, 14.7%) and no strains were found to belong to group B1. The distribution of phylogenetic groups in our study suggests that although the majority of strains were commensals, the prevalence of enteropathogenic and extra-intestinal pathotypes was noteworthy. Therefore, the role of E. coli in human infections including diarrhea, urinary tract infections and meningitis should be considered.


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