The Lebanese Trifolium purpureum: An Effective Source to Fight Escherichia coli and Associated Biofilms.

BACKGROUND

This study aimed to investigate the antibacterial and antibiofilm activities of Trifolium purpureum against Escherichia coli.

METHODS

T. purpureum Loisel. was collected from the mountains of western Lebanon. The plant parts were then extracted by maceration in 70% ethanol and water. The plant fractions were screened for secondary metabolite classes. The antibacterial activity of the extracts was determined using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Antibiofilm activity was assessed using a colorimetric method, and the effects of T. purpureum extracts on the expression of genes involved in biofilm formation in E. coli were assessed by real-time quantitative polymerase chain reaction (qPCR).

RESULTS

Coumarins, tannins, volatile oils, and phenols were absent in T. purpureum; resins were detected only in the flowers, alkaloids were detected in all plant parts except the stems, and saponins, terpenoids, and flavonoids were found in all plant parts. Regarding antibacterial activity, although all extracts had measurable MIC values, only the whole-plant water extract exhibited a bactericidal effect. Furthermore, the water and ethanol extracts exhibited variable biofilm-prevention activity, with minimum biofilm prevention concentration (MBPC) values ranging from 30 to 68.9 mg/mL. Biofilm eradication activity also varied, with minimum biofilm eradication concentration (MBEC) values ranging from 0.13 to 49.65 mg/mL corresponding to 47.3-66.8% eradication. Finally, the whole-plant water extract suppressed the expression of fimA, fimH, and flu in both planktonic cells and cells within established E. coli biofilms.

CONCLUSIONS

Our results demonstrate that T. purpureum is rich in secondary metabolites and has notable antibacterial and antibiofilm potential against E. coli, especially at the molecular level. These findings suggest that T. purpureum may be a promising candidate for use as an alternative antibacterial and antibiofilm agent.