The present study explored the effect of quercetin on the expression of virulence genes actA, inlA, inlC, and their regulatory components, sigB and prfA, in L. monocytogenes. Furthermore, the physicochemical changes on the surface, membrane permeability, and biofilm formation of quercetin-treated bacteria were evaluated. An inhibitory dose-dependent effect of quercetin (0.1-0.8 mM) was observed on the cell attachment on stainless steel at 2 and 6 h at 37 °C. Quercetin at 0.8 mM prevented the biofilm formation on stainless steel surfaces after 6 h of incubation at 37 °C, while the untreated bacteria formed biofilms with a cell density of 5.1 Log CFU/cm2. The microscopic analysis evidenced that quercetin at 0.2 mM decreased the biovolume and covered area of the attached micro-colonies. Also, sigB, prfA, inlA, inlC, and actA genes were downregulated by 7-29 times lower compared to untreated bacteria. In addition, quercetin decreased the superficial cell charge, increased the membrane permeability, and its surface hydrophobicity. These results demonstrated that quercetin prevented biofilm formation, repressed the genes of stress and virulence of L. monocytogenes and also altered the physicochemical cell properties.

中文翻译：

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槲皮素抑制应激反应因子（sigB）和毒力基因（prfA，actA，inlA和inlC），降低单核细胞增生李斯特氏菌的黏附和生物膜形成。

本研究探讨了槲皮素对单核细胞增生李斯特氏菌中毒力基因actA，inlA，inlC及其调节成分sigB和prfA表达的影响。此外，评价了经槲皮素处理的细菌的表面物理化学变化，膜通透性和生物膜形成。在37°C下2和6小时，观察到槲皮素（0.1-0.8 mM）对不锈钢上细胞附着的抑制剂量依赖性作用。在37 mC孵育6 h后，槲皮素浓度为0.8 mM阻止了不锈钢表面上的生物膜形成，而未经处理的细菌形成了细胞密度为5.1 Log CFU / cm2的生物膜。显微镜分析表明，槲皮素的浓度为0.2 mM时，其生物量和附着的微菌落的覆盖面积均减小。此外，sigB，prfA，inlA，inlC，与未经处理的细菌相比，actA和actA基因的表达下调了7-29倍。此外，槲皮素减少了表层细胞的电荷，增加了膜的通透性及其表面疏水性。这些结果表明槲皮素阻止了生物膜的形成，抑制了单核细胞增生李斯特菌的应激基因和毒力基因，还改变了理化细胞的特性。