en Gastroentrology Gastroentrology پژوهشي Original Article <div style="text-align: justify;"><span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="line-height:2;">Colorectal Cancer (CRC) is the third most common cancer around the world. Among the various factors associated with the development of CRC, bacterial infection and related toxins are considered the most critical risk factors. Several virulence genes, including fimC, cnf1, vat1, hlyD, clbB, clbN, feoA, feoB, fyuA, iroN, ireA, iutA, KpsMT (k1), KpsMTII, and KpsMTIII, have been found to have a more significant influence on the pathogenicity of the bacteria. This research aimed to assess the possible position performed through a few virulence genes in E. coli isolated from the intestinal tissues&#39; biopsies of patients with colorectal cancer. Using microbial and biochemical methods, this study isolated 82 samples of E. coli from all of the 170 biopsies obtained from patients suffering from CRC, inflammatory bowel disease, and normal individuals. Then, the frequency of 15 virulence genes was assessed by applying PCR. The obtained results indicated that two types of bacterial genes as following are more likely to be involved in CRC development: clbB and clbN genes, which are associated with the colibactin polyketide synthesis system, as well as KpsMTIII gene, which is involved in polysaccharide capsule synthesis. In precis, these consequences suggest that the superiority of E. coli containing clbB, clbN, and KpsMTIII plays an extensive role in the inflammation and, therefore, the occurrence of CRC.</span></span></span></div> Escherichia coli (E. coli), Intestine's inflammatory disease (IBD), Virulence genes, Colorectal cancer (CRC) 63 69 http://ijbc.ir/browse.php?a_code=A-10-1058-1&slc_lang=en&sid=1 Mohammad Khalilolahi pooya_780@yahoo.com 100319475328460012182 100319475328460012182 No Department of Microbiology, Islamic Azad University, North Tehran Branch, Tehran, Iran. Fatemeh Ashrafi mnfa.ashrafi@yahoo.com 100319475328460012183 100319475328460012183 No Department of Microbiology, Islamic Azad University, North Tehran Branch, Tehran, Iran. Arash Moradi 100319475328460012184 100319475328460012184 No Departments of Molecular Medicine, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran. Jean-Philippe Nougayre`de jean-philippe.nougayrade@inrae.fr 100319475328460012185 100319475328460012185 No INRA, UMR1225, F-31076 Toulouse, France, and Universite´ de Toulouse, ENVT, UMR1225, F-31076 Toulouse, France Shahla Mohammad ganji shahla@nigeb.ac.ir 100319475328460012186 100319475328460012186 Yes Departments of Molecular Medicine, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran