Itaconic acid (IA), a metabolite generated by the tricarboxylic acid (TCA) cycle in eukaryotic immune cells, and its derivative dimethyl itaconate (DI) exert antibacterial functions in intracellular environments. Previous studies suggested that IA and DI only inhibit bacterial growth in carbon-limited environments; however, whether IA and DI maintain antibacterial activity in carbon-enriched environments remains unknown. Here, IA and DI inhibited the bacteria with minimum inhibitory concentrations of 24.02 mM and 39.52 mM, respectively, in a carbon-enriched environment. The reduced bacterial pathogenicity was reflected in cell membrane integrity, motility, biofilm formation, AI-2/luxS, and virulence. Mechanistically, succinate dehydrogenase (SDH) activity and fumaric acid levels decreased in the IA and DI treatments, while isocitrate lyase (ICL) activity was upregulated. Inhibited TCA circulation was also observed through untargeted metabolomics. In addition, energy-related aspartate metabolism and lysine degradation were suppressed. In summary, these results indicated that IA and DI reduced bacterial pathogenicity while exerting antibacterial functions by inhibiting TCA circulation. This study enriches knowledge on the inhibition of bacteria by IA and DI in a carbon-mixed environment, suggesting an alternative method for treating bacterial infections by immune metabolites.

衣康酸（IA）是真核免疫细胞中三羧酸（TCA）循环产生的代谢产物，其衍生物衣康酸二甲酯（DI）在细胞内环境中发挥抗菌功能。之前的研究表明，IA 和 DI 只能抑制碳限制环境中的细菌生长；然而，IA 和 DI 在富碳环境中是否保持抗菌活性仍不清楚。在此，在富碳环境中，IA 和 DI 抑制细菌的最低抑制浓度分别为 24.02 mM 和 39.52 mM。细菌致病性的降低反映在细胞膜完整性、运动性、生物膜形成、AI-2/luxS 和毒力上。从机制上讲，IA 和 DI 处理中琥珀酸脱氢酶 (SDH) 活性和富马酸水平下降，而异柠檬酸裂解酶 (ICL) 活性上调。通过非靶向代谢组学还观察到 TCA 循环受到抑制。此外，与能量相关的天冬氨酸代谢和赖氨酸降解受到抑制。总之，这些结果表明IA和DI通过抑制TCA循环来降低细菌致病性，同时发挥抗菌功能。这项研究丰富了关于碳混合环境中 IA 和 DI 抑制细菌的知识，提出了一种通过免疫代谢物治疗细菌感染的替代方法。