Study on the inhibitory mechanism of combined ultrasound and capsaicin against Listeria monocytogenes

Listeria monocytogenes (LM) is a critical foodborne pathogen, whose exceptional environmental adaptability and biofilm-forming capacity render it resistant to effective control during food processing and storage. Sonodynamic therapy (SDT), as an emerging sterilization approach, has rapidly emerged demonstrating potent microbicidal efficacy against microorganisms. The development of novel sonosensitizers is of crucial significance for the further advancement and application of SDT. This study is the first to demonstrate that capsaicin acts as a sonosensitizer, significantly enhancing its anti-LM efficacy under ultrasound irradiation. Results demonstrate that ultrasound combined with capsaicin treatment effectively eliminates LM, suppresses its motility, and impedes biofilm formation and adhesion. This study elucidates capsaicin's antibacterial mechanism as a sonosensitizer against LM, showing that ultrasound combined with capsaicin treatment substantially elevates bacterial oxidative stress levels, increases cell membrane permeability, disrupts cellular architecture, and induces damage to bacterial DNA and proteins, ultimately leading to bacterial death. Molecular mechanism analysis indicates that Ultrasonic-activated capsaicin treatment significantly downregulates genes associated with bacterial quorum sensing systems and motility. Through its application in milk, its potential as an effective bactericide was further demonstrated. This study not only provides novel strategies for the prevention and control of LM and its biofilms but also offers a critical theoretical foundation and practical guidance for developing natural sonosensitizers, which paves the way for broader applications of sonodynamic technology in food safety and microbial control.