Molecular investigation of the prevalence and detection of enterohemorrhagic Escherichia coli isolated from traditional cheese in Iran

Introduction: Shiga toxin-producing Escherichia coli (STEC) strains are one of the main causes of food poisoning and diseases such as hemorrhagic colitis and hemolytic uremic syndrome.  Food contamination mainly occurs through food of animal origin such as meat and dairy products. The aim of this study was to investigate prevalence and distribution of virulence genes in Escherichia coli isolates from traditional cheese from Semnan city, using multiplex PCR method. Materials and Methods: In this study, a total of 100 traditional cheese samples were screened for E. coli strains through conventional microbiological tests. Then, screening for virulence genes (Stx1, Stx2, eaeA and hlyA genes) was carried out by using PCR method. Results: Fifty-nine Escherichia coli strains were identified among 100 cheese samples. Of these, 55 isolates exhibited for one or more virulence genes (93.2%) which, 44 isolates carrying more than of one gene and 11 isolates were positive for the carrier of one gene. Stx2 showed the highest frequency of virulence gene in E. coli isolates. Conclusion: Therefore, due to the high prevalence of virulence genes in pathogenic E. coli isolates in traditional cheese, it is necessary to use molecular methods to control the microbial quality of these products.