Cyclomodulins, Colibactin, and Biofilm-Associated Genes in E. coli from Colorectal Cancer and Precancerous Lesions

Introduction:Colorectal cancer (CRC) remains a significant global health challenge.Specific strains of Escherichia coli elaborating virulence factors, including cyclomodulins and colibactin, have been increasingly implicated in CRC pathogenesis.This study aimed to determine the prevalence of genes encoding these toxins, namely cnf1, cdtB-I, and clbB, alongside genes associated with biofilm formation, csgA and flu, in clinical E. coli isolates from patients diagnosed with CRC or precancerous lesions.Methods: A total of 44 E. coli isolates were obtained from colorectal tissue biopsies of patients diagnosed with CRC or precancerous polyps, and from healthy controls.PCR was employed to screen for the presence of the toxin-encoding genes cnf1, cdtB-I, and clbB, as well as the biofilm-associated genes csgA and flu.Biofilm formation was assessed quantitatively utilizing a standard microtiter plate assay.Results: The toxin-encoding genes cnf1 and cdtB-I were each detected in 14 isolates (31.8%) across all study groups (CRC, polyp, and healthy controls).In contrast, the clbB gene was identified in 5 isolates (11.4%), exclusively within the polyp and healthy control groups.The biofilm-associated genes csgA and flu exhibited the highest prevalence, being detected in 41 (93.2%) and 22 (50.0%)isolates, respectively, across all groups.Notably, none of the tested isolates demonstrated biofilm formation capability under the experimental conditions employed.Conclusions: This study demonstrated the presence of the cdtB-I gene in E. coli isolates from both early-stage CRC (stages I and II), with a notably higher prevalence in stage I. Furthermore, cdtB-I was also detected in precancerous polyps classified as both high-grade dysplasia (HGD) and lowgrade dysplasia (LGD).Intriguingly, the clbB gene was conspicuously absent from all CRC isolates of stages I and II.These findings suggest a potential role for cdtB-I in the early stages of CRC development, warranting further research to elucidate its precise impact on the progression of CRC.The presence of these virulence-associated genes, without significant differences across groups, underscores the complexity of E. coli's involvement in colorectal carcinogenesis.