Background: According to the World Health Organization, the prevalence of colorectal cancer (CRC) is the third-most common cancer in Iran. The population of Escherichia coli strains of the B2 phylogenetic group as one of the components of gut microbiota is increased in the gut of people with CRC and can also play a role in the process of cancerous intestinal cells or malignancy. The most common concern about treating infections and their association with cancer is multidrug resistance (MDR). Methods: In this study, stool samples of 20 patients with CRC were examined for sensitivity to 9 antibiotics and their genotypes were determined. Results: More than 90% of the isolates were MDR. Although among 20 isolates of E. coli gut flora in CRC patients, 11 (55%), 7 (35%), 0 (0%), and 2 (10%) strains belonged to phylogenetic groups B2, D, B1, and A, respectively. Conclusions: There was no significant relationship between the B2 phylogenetic group and MDR. Furthermore, the closeness of the species based on >90% similarity, seven clusters were observed that among five clusters, similarities were observed in terms of the phylogenetic group.

Background Colorectal cancer ranks third globally among all types of cancers. Dysbiosis of the gut microbiota of people with CRC is one of the effective agents in the tumorigenesis and metastasis in this type of cancer. The population of Escherichia coli strains, a component of gut microbiota, is increased in the gut of people with CRC compared with healthy people. So, E.coli strains isolated from these patients may have a role in tumorigenesis. Because the most isolated strains belong to the B2 phylogenuetic group, there seems to be a linkage between the bacterium components and malignancy. Material and methods In this study, the proteomic comparison between isolated Ecoli from CRC patients and healthy people was assayed. The isolated spot was studied by Two-dimensional gel electrophoresis (2DE) and Liquid chromatography-mass spectrometry (LC–MS). The results showed that the expression of Outer membrane protein A (OmpA) protein increased in the commensal E.coli B2 phylogenetic group isolated from CRC patients. Additionally, we analyzed the effect of the OmpA protein on the expression of the four genes related to apoptosis in the HCT116 colon cancer cell line. Results This study identified that OmpA protein was overexpressed in the commensal E.coli B2 phylogenetic group isolated from CRC patients compared to the E.coli from the control group. This protein significantly decreased the expression of Bax and Bak, pro-apoptotic genes, as well as the expression of P53 in the HCT116 Cell Line, P < 0.0001. LC–MS and protein bioinformatics results confirmed that this protein is outer membrane protein A, which can bind to nucleic acid and some of the organelle proteins on the eukaryotic cell surface. Conclusions According to our invitro and insilico investigations, OmpA of gut E.coli strains that belong to the B2 phylogenetic group can affect the eukaryotic cell cycle.