Evaluation of cinnamon extract effects on clbB gene expression and biofilm formation in Escherichia coli strains isolated from colon cancer patients

BACKGROUND: Colon cancer is one of the most common malignancies and the fourth leading cause of cancer-related mortality in the world. Colibactin, which is synthesized by the pks genomic island of E. coli interfere with the eukaryotic cell cycle. Cinnamon has an antimicrobial effect and considered as a colon cancer-preventing agent. The aim of the study was to evaluate the effects of cinnamon extract and cinnamaldehyde on clbB gene expression and biofilm formation in clinical isolates of E. coli. METHODS: Thirty E. coli carrying pks gene were isolated from the colon cancer patients, inflammatory bowel disease and healthy subjects. Antibiotic susceptibility was evaluated by disk diffusion method and the minimum inhibitory concentration of cinnamon essential oil and cinnamaldehyde by microdilution broth method. In vitro biofilm formation of E.coli isolates was monitored using a microtiter plate method. The presence of clbB, clbA and clbQ genes in E.coli isolates were evaluated by PCR. The effect of cinnamaldehyde and cinnamon essential oil on clbB gene expression was evaluated by Real-Time PCR. RESULTS: The highest antibiotic resistance was obtained with 94.4% for ticarcillin-clavulanic acid, azithromycin, amoxicillin, and amikacin. The MIC for all clinical isolates was 32 μl/ml of cinnamon essential oil and the MIC of cinnamaldehyde was between 0.00002 to 0.03 μl/ml. After exposure of isolates to cinnamon extract and cinnamaldehyde, 40 and 13.3% were weakly biofilm producers, respectively. The frequencies of clbB, clbA, and clbQ genes were 23.3, 23.3, and 26.7%, respectively. The expression of clbB gene in the presence of the Sub-MIC concentration of cinnamon essential oil and cinnamaldehyde was decreased in 8 isolates compared to untreated isolates (p-value < 0.05). CONCLUSIONS: The antibacterial activity of cinnamaldehyde and cinnamon essential oil allows the use of these herbal compounds for treatment or supplements in infections caused by E. coli and in patients with suspected colorectal cancer.