Abstract
Background: The present study aimed to investigate the effect of thymol on growth inhibition, biofilm inhibition, and antibiotic sensitivity of Escherichia coli isolated from urinary tract infection in Gilan province, Iran.
Methods: The disc diffusion and broth microdilution methods were used to investigate the antimicrobial effect of thymol on 30 urinary tract infection isolates of E. coli. Additionally, the time-kill assay was used to investigate the effectiveness of thymol at different time intervals over a period of 24 hours. The anti-biofilm effect of thymol was investigated using the microplate method. Moreover, the effect of thymol on fimH gene expression was investigated. To investigate the effect of thymol on the sensitivity of E. coli isolates to cefotaxime and ciprofloxacin, the checkerboard assay was used.
Results: ThymolFF exhibits inhibitory effects on the growth of E. coli isolates and the diameter of the zone of growth inhibition caused by 5 mg of thymol in the studied isolates varied between 15 and 30 mm and minimum inhibitory concentration (MIC) of thymol against MDR E. coli isolates ranged from 1 to 4 mg/mL. Depending on the concentration and the exposure time, bacterial killing was promoted by thymol treatment. The use of thymol decreased the biofilm formation of the isolates by more than 50% compared to the control and also bacterial treatment with thymol led to down-regulation of the fimH gene. Furthermore, enhancing the antibacterial effect of cefotaxime and ciprofloxacin by thymol was demonstrated.
Conclusion: The present study found that thymol, a terpenoid of plant origin, exhibited strong killing efficiency, inhibiting the biofilm formation, and enhanced antibiotic sensitivity of E. coli isolated from urinary tract infection.