Modulation of Quorum Sensing and Virulence Gene Expression in Escherichia coli by Extracts of Physalis alkekengi.

Abstract

The rise of multidrug-resistant (MDR) bacteria underscores the need for new antimicrobials. In uropathogenic Escherichia coli, quorum sensing and adhesion play central roles in pathogenicity; therefore, luxS and fimH were selected as virulence targets. This study examined the antibacterial, antibiofilm and gene-modulating effects of ethanolic and aqueous root extracts of Physalis alkekengi L. against three E. coli isolates (EC1, EC2, EC3). Phytochemical analysis confirmed the presence of phenolics, flavonoids, flavonols and anthocyanins, along with measurable antioxidant capacity. Antimicrobial activity was assessed using agar well diffusion, disk diffusion and broth microdilution on the MDR isolate EC2. Biofilm inhibition was quantified using a microtiter plate, and changes in luxS and fimH expression were evaluated by real-time PCR. The ethanolic extract contained higher flavonoid and flavonol levels, whereas the aqueous extract was richer in phenolics. Anthocyanins and DPPH activity were undetectable in both extracts. The ethanolic extract completely inhibited EC3 at 10 mg/mL, although no MBC was observed for EC1, EC2 or any isolate exposed to the aqueous extract. In EC2, the ethanolic extract produced larger but variable inhibition zones, reduced biofilm by approximately 63% and significantly downregulated luxS and fimH (p < 0.05), supporting the potential of P. alkekengi as a natural antivirulence agent.