原儿茶酸对副溶血弧菌的抑菌和减毒作用

该研究旨在探讨原儿茶酸对副溶血弧菌的抑菌活性和减毒作用，揭示原儿茶酸抑菌的作用机制。通过测定最小抑菌浓度（Minimal Inhibitory Concentration，MIC）、生长曲线、核酸与蛋白质泄漏量、丙二醛（MDA）含量，利用扫描电镜观察副溶血弧菌形态的变化，来评估原儿茶酸对副溶血弧菌的抑菌活性及其对细胞膜完整性和通透性的影响。同时，通过检测亚抑菌浓度（Sub-inhibitory Concentrations，SICs）下原儿茶酸对副溶血弧菌毒力因子合成的影响，研究原儿茶酸对副溶血弧菌的毒力衰减作用。实验结果表明，原儿茶酸的MIC为2 mg/mL，经MIC浓度原儿茶酸处理后，副溶血弧菌发生严重内陷和破裂，上清液中核酸、蛋白质、MDA含量分别是对照组的2.65倍、1.94倍和10.05倍。此外，原儿茶酸在浓度为1/4 MIC时对胞外多糖、胞外蛋白酶、生物被膜的抑制率分别为40.57%、19.79%和26.04%，在浓度为1/2 MIC时的抑制率分别为52.85%、28.38%和34.69%。原儿茶酸主要作用于细胞膜，通过影响细胞膜的完整性和通透性抑制副溶血弧菌的生长，在亚抑菌浓度下便可有效减弱副溶血弧菌毒力。

Antibacterial and Virulence-attenuating Effects of Protocatechuic Acid against Vibrio parahaemolyticus

In order to reveal the mechanisms underlying the antibacterial function of protocatechuic acid (PCA), the antimicrobial activity and virulence-attenuating effect of PCA was investigated. To evaluate the antibacterial activity of PCA against Vibrio parahaemolyticus and its effect on the integrity and permeability of cell membranes, the minimal inhibitory concentration (MIC), growth curve, nucleotide and protein leakage, and malondialdehyde (MDA) content were measured, and the morphological changes of V. parahaemolyticus were examined by scanning electron microscopy. Meanwhile, the virulence-attenuating effect of PCA against V. parahaemolyticus was further investigated through detecting the effects of PCA at sub-inhibitory concentrations (SICs) on the synthesis of virulence factors of V. parahaemolyticus. The experimental results showed that the MIC of PCA against V. parahaemolyticus was 2 mg/mL. After the treatment with PCA at MIC, V. parahaemolyticus was severely invaginated and ruptured. The contents of nucleic acid, protein, and MDA in the supernatant were 2.65 times, 1.94 times, and 10.05 times those of the control group, respectively. In addition, the inhibition rates of PCA against extracellular polysaccharides, extracellular proteases, and biofilms were 40.57%, 19.79%, and 26.04%, respectively, at a PCA concentration of 1/4 MIC, and 52.85%, 28.38% and 34.69%, respectively, at a PCA concentration of 1/2 MIC. PCA mainly acted on cell membrane, inhibited the growth of V. parahaemolyticus through affecting the integrity and permeability of the cell membrane, and at sub-inhibitory concentrations reduced effectively the virulence of V. parahaemolyticus.