Molecular Study of clbS and clbA genes in the E.coli bacteria isolated from tissue of patients with colorectal cancer

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. 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. 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). 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.