Escherichia coli and Enterobacter cloacae are major foodborne pathogens and can form challenging single/mixed biofilms. A recent study demonstrated that luteolin (LUT) exhibits antibacterial activities against some pathogens; however, the mechanisms underlying the effects of LUT on planktonic and biofilm bacteria have never been fully elucidated. This study aimed to determine the antibacterial activity and its mechanism of action against E. coli and E. cloacae. Here, the antimicrobial mode of LUT was explored by evaluating alterations in both cell membrane integrity and cell morphology, and the antibiofilm activity of LUT was investigated using quantitative and qualitative assays. The results showed that minimal inhibitory concentration and minimum bactericidal concentration values of LUT against E. coli were 64 and 128 μg/mL and 128 and 256 μg/mL for E. cloacae mono- and dual-species, respectively. LUT impaired cell membrane integrity, as demonstrated by the remarkable increase in the number of membrane-damaged cells and definite variations in cell morphology. Moreover, LUT presented robust inhibitory effects on biofilm formation and the capacity to kill mono- and dual-species biofilm cells. Overall, these data show the potential benefit of using a natural antimicrobial and/or preservative in the food industry, LUT, to control mono- and mixed-species or biofilm-associated infections.

大肠杆菌和阴沟肠杆菌是主要的食源性病原体，可以形成具有挑战性的单一/混合生物膜。最近的一项研究表明，木犀草素 (LUT) 对某些病原体具有抗菌活性；然而，LUT 对浮游细菌和生物膜细菌影响的潜在机制尚未完全阐明。本研究旨在确定对大肠杆菌和阴沟肠杆菌的抗菌活性及其作用机制. 在这里，通过评估细胞膜完整性和细胞形态的改变来探索 LUT 的抗菌模式，并使用定量和定性分析研究 LUT 的抗生物膜活性。结果表明，LUT对大肠杆菌的最低抑菌浓度和最低杀菌浓度分别为64和128 μg/mL，对阴沟肠杆菌分别为128和256 μg/mL分别为单种和双种。LUT 损害了细胞膜的完整性，正如膜受损细胞数量的显着增加和细胞形态的明确变化所证明的那样。此外，LUT 对生物膜形成和杀死单物种和双物种生物膜细胞的能力具有强大的抑制作用。总的来说，这些数据显示了在食品工业 LUT 中使用天然抗菌剂和/或防腐剂来控制单一和混合物种或生物膜相关感染的潜在好处。