Frequency of Shiga Toxin-Producing Genes of Escherichia Coli Isolated from Diarrheic Stools of Iranian Children by PCR

Objective: Shiga toxin-producing E. coli (STEC) is a pathogenic E. coli that may cause hemolytic uremic syndrome (HUS) after diarrheal disease through Shiga toxins. Management of the patients with STEC infection is different from that of other diarrheal diseases due to increase in frequency of HUS after antibiotic administration. Few studies were conducted in Iran and epidemiology of STEC remains obscure; this necessitates examination of stools especially in young children for this bacterium. Methods: We determined the frequency of STEC in 947 E. coli strains isolated from diarrheal stools of children less than 14 years in Tehran with conventional culture methods and multiplex-PCR via determining the STX1 and STX2 genes, between October 2008 and September 2009. We also evaluated the association between stool exam findings and presence of STEC. Findings: Twenty seven (2.8%) of E. coli isolates were positive for STX1 or STX2 genes, most of which occurred in spring (P<0.05). There was no significant association between STEC positivity and stool exam findings. Eighteen out of 27 (66.7%) Shiga toxin positive samples were isolated from males and the rest from females. The most common STX-positive diarrheal samples showed loose consistency (P<0.017). Conclusion: Although the low frequency of STEC in our population indicates that it is not a major problem in our population, STEC should be regarded as an important infection because of its severe consequences. Further studies with greater sample size are needed to confirm our results.