Antibacterial mechanism of action of perilla leaf essential oil on Shigella flexneri and its preservation effectiveness in fresh-cut lettuce.

Shigella flexneri is a major foodborne pathogen and a leading cause of bacillary dysentery in developing countries, typically transmitted via contaminated water and fresh produce. Although perilla leaves-used as both food and medicine-are rich in bioactive compounds, the antimicrobial and antibiofilm activities of perilla leaf essential oil (PLEO) against S. flexneri remain unclear. This study investigated the antibacterial mechanisms of PLEO against S. flexneri and evaluated its potential for use in preserving fresh-cut lettuce. Gas chromatography-mass spectrometry (GC-MS) analysis identified d-limonene, terpinolene, and p-cymene as the major constituents of PLEO. Morphological and physiological assays demonstrated that PLEO compromises bacterial membrane integrity in a dose-dependent manner, resulting in cytoplasmic leakage, membrane depolarization, and intracellular ATP depletion. PLEO also induced oxidative stress by increasing reactive oxygen species accumulation and inhibiting catalase activity. Untargeted metabolomics revealed that PLEO acts through multiple pathways, notably perturbing amino acid, lipid, and energy metabolism. Additionally, PLEO strongly inhibited biofilm formation and disrupted established mature biofilms on various surfaces. Application of PLEO to fresh-cut lettuce significantly reduced S. flexneri counts and delayed quality deterioration during storage at 4 °C. These results indicate that PLEO is a promising natural, multi-target antibacterial agent for food safety control and an environmentally friendly approach to produce preservation.