Antibacterial activity and mechanism of rutin in UV‑A light treatment against Escherichia coli O157:H7

Abstract

The antibacterial strategy that utilizes ultraviolet-A (UVA)-irradiated natural photosensitizers is promising, being particularly effective against multidrug-resistant pathogens with high bactericidal efficiency and minimal resistance-inducing risk. Rutin is a natural flavonoid with wide availability, low cytotoxicity, and diverse pharmacological activities, making it a promising photosensitizer; however, its UVA-induced photodynamic antibacterial properties remain underexplored. The aim of this study is to systematically evaluate the antibacterial efficacy and mechanism of UVA-Rutin against foodborne Escherichia coli O157:H7. In the study, Fourier transform infrared spectroscopy and Raman spectroscopy were used to characterize structural alterations in rutin post-UVA irradiation, focusing on functional groups relevant to photodynamic activity. Antibacterial efficacy was assessed via standardized assays including minimum inhibitory concentration (MIC) determination, while biocompatibility was evaluated using MTT cytotoxicity assays. To confirm the antibacterial effects, physiological/structural perturbations of bacteria were measured, including cell membrane integrity, DNA damage, motility, biofilm formation, and extracellular polysaccharide (EPS) production, as well as the generation of intracellular reactive oxygen species (ROS) measured using fluorescent probes. Reverse transcription quantitative polymerase chain reaction was used to analyze key virulence- and quorum sensing-related genes (luxS, phoP, qseB, qseC). Results showed that UVA-induced structural changes enhanced the photosensitizing activity of rutin. UVA-Rutin exhibited significant antibacterial activity (low MIC) and good biocompatibility, triggering the generation of massive intracellular ROS, disrupting cell membranes, inducing DNA damage, impairing motility, inhibiting biofilm/EPS production, and downregulating target genes. Collectively, UVA-Rutin exerts potent antibacterial effects via ROS-mediated structural/functional disruption and virulence gene regulation, highlighting its potential as a novel food industry antibacterial agent.

Keywords: Escherichia coli O157:H7; Antibacterial activity; ROS; Rutin; UVA.