Salmonella enterica serovar Typhimurium (ST) remains a major infectious agent in the USA, with an increasing antibiotic resistance pattern, which requires the development of novel antimicrobials capable of controlling ST. Polyphenolic compounds found in plant extracts are strong candidates as alternative antimicrobials, particularly phenolic acids such as gallic acid (GA), protocatechuic acid (PA) and vanillic acid (VA). This study evaluates the effectiveness of these compounds in inhibiting ST growth while determining changes to the outer membrane through fluorescent dye uptake and scanning electron microscopy (SEM), in addition to measuring alterations to virulence genes with qRT-PCR. Results showed antimicrobial potential for all compounds, significantly inhibiting the detectable growth of ST. Fluorescent spectrophotometry and microscopy detected an increase in relative fluorescent intensity (RFI) and red-colored bacteria over time, suggesting membrane permeabilization. SEM revealed severe morphological defects at the polar ends of bacteria treated with GA and PA, while VA-treated bacteria were found to be mid-division. Relative gene expression showed significant downregulation in master regulator hilA and invH after GA and PA treatments, while fliC was upregulated in VA. Results suggest that GA, PA and VA have antimicrobial potential that warrants further research into their mechanism of action and the interactions that lead to ST death.

中文翻译：

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酚类物质对肠炎沙门氏菌鼠伤寒沙门氏菌的抗菌和抗毒作用

肠沙门氏菌血清鼠伤寒（ST）仍然是美国的主要传染源，其抗生素耐药性模式不断增强，这就需要开发能够控制ST的新型抗菌剂。在植物提取物中发现的多酚化合物是替代抗菌剂的强力候选者，尤其是酚酸，例如没食子酸（GA），原儿茶酸（PA）和香草酸（VA）。这项研究评估了这些化合物在抑制ST生长方面的功效，同时通过荧光染料摄取和扫描电子显微镜（SEM）确定了外膜的变化，此外还使用qRT-PCR测量了毒力基因的变化。结果表明，所有化合物均具有抗菌潜力，显着抑制了ST的可检测生长。荧光分光光度法和显微术检测到相对荧光强度（RFI）和红色细菌随时间增加，表明膜通透。扫描电镜显示在用GA和PA处理过的细菌的极性末端存在严重的形态缺陷，而用VA处理过的细菌被发现处于中间区域。相对基因表达在主调节子中显着下调肺门和invH后GA和PA治疗，同时的fliC在VA上调。结果表明，GA，PA和VA具有抗菌潜力，值得进一步研究其作用机理以及导致ST死亡的相互作用。