Background: Enterotoxigenic Escherichia coli (ETEC) is responsible for piglet diarrhea and causes substantial economic loss in the pig industry. Along with the restriction of antibiotics, natural compounds targeting bacterial virulence factors are supposed to be efficacious and attractive alternatives for controlling ETEC infection. This study aimed to investigate the influence of dihydromyricetin (DMY), a natural flavonoid compound, on the expression of virulence factors of ETEC and intestinal inflammatory injury.

Results: DMY interfered with the quorum sensing (QS) of ETEC K88 since it decreased AI-2 secretion and downregulated the expression of LuxS and Pfs, which dominate AI-2 production, and decreased the expression mRNA level of genes (lsrA, lsrB, lsrC, lsrD, lsrK, and lsrR) that are involved in AI-2 internalization and signal transduction. Additionally, DMY markedly dampened the expression of QS-related virulence genes (elt-1, estB, fliC, faeG), biofilm formation, cell adhesion, and stress tolerance of ETEC K88. Furthermore, DMY treatment applied to the ETEC K88 infection in mice model resulted in decreased amount of heat-labile (LT) and heat-stable (ST) enterotoxins, reduced production of cAMP and cGMP, downregulated protein level of CFTR and upregulated expression of NHE3 in the ileum. In addition, the mRNA expression of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) and histological damage in the ileum were significantly decreased by DMY treatment.

Conclusions: DMY can inhibit the AI-2 QS and virulence factor expression, thereby attenuating the virulence of ETEC and alleviating intestinal inflammatory damage in ETEC K88-challenged mice. This study indicated that DMY has the potential to be a promising antivirulence agent for combating ETEC infection.

Keywords: Dihydromyricetin; ETEC; Intestinal inflammation; Quorum sensing; Virulence factor.

© 2025. The Author(s).

背景： 肠毒素性大肠杆菌（ETEC）是导致仔猪腹泻的原因，并在养猪业中造成巨大的经济损失。随着抗生素使用的限制，针对细菌毒力因子的天然化合物被认为是有效且具有吸引力的替代品，用于控制ETEC感染。本研究旨在探讨二氢杨梅素（DMY），一种天然黄酮类化合物，对ETEC毒力因子表达和肠道炎症损伤的影响。

结果： DMY干扰了ETEC K88的群体感应（QS），因为它降低了AI-2的分泌并下调了LuxS和Pfs的表达，这两种蛋白主要负责AI-2的产生，并且减少了参与AI-2内化和信号转导基因（lsrA、lsrB、lsrC、lsrD、lsrK和lsrR）的mRNA水平。此外，DMY显著降低了与QS相关的毒力基因（elt-1、estB、fliC、faeG）、生物膜形成、细胞黏附以及ETEC K88的压力耐受性表达。另外，在感染ETEC K88的小鼠模型中使用DMY治疗导致热不稳定（LT）和热稳定（ST）肠毒素的数量减少，环磷酸腺苷（cAMP）和环磷酸鸟苷（cGMP）的产生减少，回肠中的CFTR蛋白水平下调以及NHE3表达上调。此外，在回肠中的促炎细胞因子（TNF-α、IL-1β和IL-6）mRNA表达及组织学损伤均显著降低。

结论： DMY可以抑制AI-2 QS和毒力因子的表达，从而减轻ETEC K88感染小鼠中的毒力并缓解肠道炎症损伤。这项研究表明DMY具有作为抗毒力剂对抗ETEC感染的潜力。

关键词： 二氢杨梅素；肠毒素性大肠杆菌；肠道炎症；群体感应；毒力因子。