Identification of serotypes and virulence markers (stx) of Escherichia coli isolated from patients with diarrhea in Shiraz, Iran

Abstract

BackgroundIn developing countries diarrheal infections with bacterial species especially enterohemorrhagic Escherichia coli (EHEC) cause severe diseases including hemorrhagic colitis, hemolytic uremic syndrome and mortality in children less than five years of age. Such life-threatening infections are due to Shiga toxin (Stx) produced by EHEC including stx1 and stx2. stx1 is identical to shiga toxin produced by Shigella dysenteriae type1. However, stx2 is different from Stx1 in immunological properties, but similar to Stx1 in biological characteristics. Both of these toxins are encoded by stx genes of lysogenic bacteriophage (Stx phage) integrated into the genome of EHEC. AimsThe aim of this study was to determine the prevalence and distribution of Stx toxins in O157:H7E.coli and non-O157:H7E. coli isolated from patients with diarrhea from 2013 to 2014 in Shiraz, Iran. Methods and materialsStool samples from 1050 children and adults patients collected from June 2014 to June 2015 were investigated for Shiga toxigenic E. coli by conventional and molecular methods. ResultsOf 1050 diarrheal specimens, 306 isolates (29.1%) was diagnosed as E. coli. Gene analysis for virulence factors showed that 38(12.4%) isolates carried Stx1, 57(18.6%) Stx2 and 13 (4.2%) harbored both Stx1 and Stx2. ConclusionsThis study showed that ETEC was potential pathogen in children aged less than five years and the relatively high prevalence of Stx1 and Stx2 producing ETEC in our region. Moreover, the higher detection rate of Stx2 indicated the important role of this gene in diarrheal diseases