Most Escherichia coli strains are innocuous to human beings; however, some strains can cause diarrhea and are grouped into pathotypes. Since current trends promote the use of natural-origin compounds to control bacteria, in this study, the effects of the phenolic compounds (PCs) tannic acid (TA), gallic acid (GA), methyl gallate (MG), and epigallocatechin gallate (EG) on the growth, swarming motility, biofilm formation, and expression of selected virulence genes of three E. coli pathotypes (enteropathogenic Escherichia coli [EPEC], enterohemorrhagic Escherichia coli [EHEC], and enterotoxigenic Escherichia coli [ETEC]) were evaluated. Minimum bactericidal concentrations (MBCs) were determined by using microtiter plates, and the effects of sublethal PC concentrations on swarming motility were evaluated on Luria-Bertani agar. Biofilm formation was assessed in microtiter plates via crystal violet staining, and the expression levels of genes involved in biofilm formation (flhC, fliA, fliC, and csgA) and swarming motility (csgD and cyaA) were evaluated via quantitative PCR. All PC were bactericidal with minimal bactericidal concentrations ranging from 0.07 to 2.1 mg/mL. At concentrations lower than the MBC, PCs decreased swarming motility (14.8–100%). GA reduced biofilm formation in all of the tested strains; however, TA, MG, and EG induced biofilm formation in some strains at specific concentrations. TA induced the overexpression of csgA, csgD, and cyaA, whereas the other PCs did not have any effects or reduced their expression levels. The PCs tested in this study showed potential to control E. coli strains belonging to the EHEC, ETEC, and EPEC pathotypes by affecting their growth, swarming motility, and virulence gene expression; however, proper concentrations must be used to avoid the induction of undesirable virulence factor genes.

中文翻译：

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具有杀菌活性的酚类物质可改变产肠毒素、肠病原性和肠出血性大肠杆菌的运动性和生物膜形成。

大多数大肠杆菌菌株对人类无害；然而，一些菌株会导致腹泻并被归类为致病型。由于当前的趋势促进使用天然来源的化合物来控制细菌，因此在本研究中，酚类化合物 (PC) 单宁酸 (TA)、没食子酸 (GA)、没食子酸甲酯 (MG) 和表没食子儿茶素没食子酸酯 ( EG) 对三种大肠杆菌致病型（肠致病性大肠杆菌[EPEC]、肠出血性大肠杆菌[EHEC] 和产肠毒素大肠杆菌）的选定毒力基因的生长、蜂群运动、生物膜形成和表达的影响[ETEC]) 进行了评估。使用微量滴定板测定最低杀菌浓度 (MBC)，并在 Luria-Bertani 琼脂上评估亚致死 PC 浓度对蜂群运动的影响。通过结晶紫染色在微量滴定板上评估生物膜形成，以及参与生物膜形成的基因（flhC、fliA、fliC和csgA）和蜂群运动（csgD和cyaA）的表达水平) 通过定量 PCR 进行评估。所有 PC 均具有杀菌作用，最低杀菌浓度范围为 0.07 至 2.1 mg/mL。在低于 MBC 的浓度下，PC 会降低蜂群运动性（14.8-100%）。GA 减少了所有测试菌株的生物膜形成；然而，TA、MG 和 EG 在特定浓度下会在某些菌株中诱导生物膜形成。TA 诱导csgA、csgD和cyaA的过表达，而其他 PC 没有任何影响或降低了它们的表达水平。本研究中测试的 PC 显示出控制大肠杆菌的潜力属于 EHEC、ETEC 和 EPEC 致病型的菌株，通过影响它们的生长、集群运动和毒力基因表达；然而，必须使用适当的浓度以避免诱导不需要的毒力因子基因。