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Aim and Background: Colorectal cancer is the third most common cancer after lung cancer, stomach and liver cancer in the world. Studies have shown that patients with inflammatory disease of the large intestine are at high risk of developing colorectal cancer are located. Several factors make inflammatory bowel disease and colorectal cancer is one of the factors involved, bacteria and toxins derived from them. Research shows that some strains of E. coli can be induced to increase the mutation rate that was established in 2010 by Cuvas-Romas and colleagues. fimC and vat1 Virulence genes in these organisms play an important role in bacteria pathogenicity. This study is to compare the virulence genes in E .coli strains isolated from samples biopsy patients' inflammatory bowel disease and colorectal cancer, intestinal tissue was performed.

Materials and Methods: 38 biopsies were obtained from intestinal tissue and E.coli bacteria in microbial and biochemical method was identified and isolated. After DNA extraction, strains for virulence genes vat1, fimC using polymerase chain reaction (PCR), were evaluated.

Results: Molecular analysis showed a significant difference between the groups studied the gene vat1 (p = 0.0245) and 42.8% of positive samples were for this gene in normal groups, 87.5% with inflammatory bowel disease87.5 % of patients with colorectal cancer were reported. But there is no significant difference between the groups in terms of fimC gene (P = 0.201). And 71.4% of positive samples for this gene in normal groups' and 93.7% in patients with inflammatory bowel disease73.3 % of patients with colorectal cancer were reported.

Conclusion: The results, to confirm the good relationship between virulence genes studied induced inflammation and proliferation by inducing mutation rate.

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Background and Aim: One of the most important factors in the development of colorectal cancer(CRC) is the bacteria and their toxins. Some strains of E. coli have the PKS gene island, which produces exotoxin called colibactin. Colibactin causes damage to the DNA and leads to the development of tumor in colorectal cancer by activating the signaling pathway. The purpose of this study was the investigation of clbS and clbA genes (two genes in the PKS Island) in E .coli isolated from colorectal tumor tissues.
Materials and Methods: For this purpose, 79 biopsy samples from tissue of patients with CRC were prepared after receiving a questionnaire and consent form. By microbial and biochemical methods, these E. coli were isolated and identified and then these bacteria were evaluated for the presence of clbA and clbS genes by PCR method.
Results: E.coli isolated were positive in point of biochemical tests; Motility, Indol, TSI, and MR tests and negative for Citrate and Urea tests. The molecular results showed the frequency of 66.67% , 40.91% and 59.09%  for clbA in normal subjects, the patients with IBD and CRC patients respectively. Moreover the frequency of  50%, 58.62% and 27.8% for the clbS gene in normal subjects, the patients with IBD and CRC patients respectively. Also 27.8% of the samples had both genes (clbA / clbS).
Discussion: Both the clbS and clbA genes are among the essential genes of the PKS Island. Considering these results and the importance of colibactin and its relation with colorectal cancer, seems the more studies in this regard is necessary.