Diffusely Adherent and Cyclomodulin-Positive Escherichia coli Are Associated with Colon Diseases

Background: Any alteration in gut microbiota may result in the colonization of certain pathobionts, leading to the development of colon diseases. Some strains of Escherichia coli are pathobionts that can contribute to the initiation or progression of colon diseases through the induction of pro-inflammatory pathways or the production of genotoxins. Objectives: The present study was performed to investigate the association between certain E. coli pathobionts (cyclomodulin-positive and afa-C+ diffusely adherent E. coli) and their characteristics with colon diseases. Methods: Stool specimens were collected from patients referred to colonoscopy centers at two university-affiliated hospitals (Yazd and Kerman, Iran). A total of 67 patients voluntarily joined the study as the target group (21 cases of colorectal cancer and 46 cases of inflammatory bowel disease), along with 67 healthy individuals. Stool samples were screened for E. coli isolates using culture techniques. Cyclomodulin-encoding genes (clbN, cnf, cdt, and cif), as well as afa-C, were detected by PCR assay. Phylogrouping, virulence gene screening, antibiotic susceptibility evaluation, and biofilm formation assessment were also performed. Results: In comparison with the control group, afa-C+ DAEC was significantly associated with CRC (n = 8, 38.1%, P = 0.001) and IBD (n = 8, 17.4%, P = 0.026). The presence of clbN (n = 4, 19%) and cnf (n = 4, 19%, P = 0.053) was relatively associated with CRC. Most of the isolates from the patient group (n = 16, 23.9%) belonged to phylogroup B2. Iron uptake-related genes were also significantly associated with isolates from patients. No significant association was found between antibiotic resistance and biofilm formation in any of the studied groups. Conclusions: This study provides preliminary data about the involvement of certain important E. coli pathobionts in colon diseases. As afa-C+ DAEC was associated with the colon diseases studied, it appears that it may be proposed as a putative marker for screening procedures. However, a definitive conclusion requires more comprehensive investigations.