Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 16 3 2024 06 19 329 336 Mojtaba Bonyadian Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, Shahrekord University, Shahrekord, Iran Farzad Isvand Haidari Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, Shahrekord University, Shahrekord, Iran Masoud Sami Department of Food Science and Technology, School of Nutrition, Isfahan University of Medical Sciences, Isfahan, Iran 2023 11 19 2024 05 09 Background and Objectives: Escherichia coli O157: H7 is one of the most important causes of hemorrhagic colitis, and hemolytic uremic syndrome. The present study aimed to isolate E. coli O157: H7 from foods and patients with hemorrhagic colitis, and identify Shiga toxin genes, phylogenetic comparison, and antibiotic resistance of the isolates. Materials and Methods: In total 400 samples, including patients stool and food were taken in Isfahan-Iran province. Phenotypic tests and PCR were performed to identify Shiga toxin-producing E. coli. The isolated strains were compared phylogenetically by PFGE. Agar disk diffusion was performed to identify the antibiotic resistance of the isolates. Results: Totally, 5 isolates of fecal samples were E. coli O157, but only 2 isolates carried H7 gene. Also, 9 isolates of E. coli O157 were isolated from food samples that 3 isolates were E. coli O157: H7. The isolates carried stx1, stx2, hlyA and eaeA genes. Also, E. coli non-O157: H7 identified from samples that contained stx1, stx2, hlyA genes. The highest susceptibility to imipenem and the highest resistance to ampicillin and ciprofloxacin were observed. There was a similarity of 100% between the E. coli O157: H7 strains isolated from patients and raw milk and minced beef samples. Conclusion: Serotypes other than the O157 of E. coli are more prevalent in patients and food. The E. coli O157: H7 isolates from patients had 100% genetic similarity with minced meat and cow milk isolates, which indicates cattle are the most important reservoir of this bacterium in Iran. https://ijm.tums.ac.ir/index.php/ijm/article/view/4489 https://ijm.tums.ac.ir/index.php/ijm/article/download/4489/1673