Coumarin and Quercetin Reduce Ciprofloxacin MIC/MBC and Downregulate the Cytolethal Distending Toxin (cdt) Gene in Ciprofloxacin-Resistant Uropathogenic Escherichia coli

Background & Objectives: Uropathogenic Escherichia coli is the major causative agent responsible for urinary tract infections that contribute to a high percentage of community-acquired and nosocomial infections. The present study aimed to assess the effect of coumarin and quercetin on the expression level of gene encoding cytolethal distending toxin (cdt) from ciprofloxacin-resistant clinical isolates of uropathogenic E. coli. Materials & Methods: From a total number of ۲۵۰ patient urine samples collected due to suspected UTI, ۱۷۷ positive cultures for uropathogenic E. coli were isolated and ۲۰ of which were positive for cdt gene. All the chemicals used for antibacterial activity assay were purchased from sigma Aldrich, and serial dilutions (۰.۱۲۵ to ۱۰۲۴ µg/mL) were prepared from stock solutions of coumarin and quercetin. The antibacterial activity of coumarin, quercetin, and ciprofloxacin was determined using broth microdilution. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) was used to estimate the level of cdt gene expression. Results: Sub-inhibitory concentrations of coumarin (۶۴ µg/mL) in combination with ciprofloxacin decreased the MIC and MBC values from ۶۴ to ۱ to ۲ µg/mL and from ۱۲۸ to ۲ to ۴ µg/mL, respectively. Similarly, sub-MIC concentrations of quercetin (۳۲ µg/mL) combined with ciprofloxacin decreased the MIC and MBC values to ۱ to ۲ and ۲ to ۴ µg/mL, respectively. Additionally, the mean fold change of cdt gene expression level in treated uropathogenic E coli was lower than the untreated bacteria by ۲.۵-fold (۱.۹ to ۳.۰-fold; p < ۰.۰۰۱) in treatment with ۶۴ µg/mL coumarin. The mean fold change of gene expression in the untreated isolates was ۱.۸ (۰.۹ to ۲.۰) fold higher than those treated with ۳۲ µg/mL quercetin (p < ۰.۰۱). The reduction in gene expression was statistically significant in both tested treatments compared with the untreated control group. Conclusion: The obtained results demonstrated that coumarin and quercetin could be considered as antibacterial agents against uropathogenic E. coli and increase the antibacterial effect of ciprofloxacin while downregulating the expression level of cdt virulence determinant. It is recommended to perform more extensive experiments in vitro and in vivo to confirm the obtained results.

کلیدواژه ها:

Herbal compounds ، Cytolethal distending toxin ، Uropathogenic Escherichia coli ، Fluoroquinolone resistance