Qian Weidong, Liu Miao, Fu Yuting, Zhang Jianing, Liu Wanting, Li Jingyuan, Li Xiang, Li Yongdong, Wang Ting
School of Food and Biological Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, PR China.
Ningbo Municipal Center for Disease Control and Prevention, Ningbo, 315010, PR China.
Microb Pathog. 2020 Feb 11;142:104056. doi: 10.1016/j.micpath.2020.104056.
Luteolin (LUT) is a naturally occurring compound found in a various of plants. Few recent studies have reported LUT antimicrobial activities against bacterial pathogens, however, the fundamental LUT mediated antimicrobial mechanism has never been elucidated. This study aimed to investigate the antimicrobial activities of LUT and its mode of action against Staphylococcus aureus and Listeria monocytogenes, either as planktonic cells or as biofilms. Here, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) of LUT against S. aureus and L. monocytogenes were determined using the broth microdilution method, and the antimicrobial mode of LUT was elucidated by evaluating the variations in both cell membrane integrity and cell morphology. Moreover, the biofilm inhibition was measured by crystal violet staining assay, while its qualitative imaging was achieved by confocal laser scanning microscope and field emission scanning electron microscope. MIC and MBC values of LUT against S. aureus were 16-32 and 32-64 μg/mL, and 32-64 and 64-128 μg/mL for L. monocytogenes. LUT destroyed the cell membrane integrity, as evidenced by a significant increase in the number of non-viable cells, and well-defined variations in cell morphology. Moreover, LUT presented robust inhibitory effects on the biofilm formation, enhanced antibiotics diffusion within biofilms and killed efficiently mono- and dual-species biofilm cells. Overall, LUT demonstrates potent antimicrobial properties on planktonic and biofilm cells, and the biofilm formation, and thus has the potential use as a natural food preservative in foods.
木犀草素（LUT）是一种存在于多种植物中的天然化合物。最近很少有研究报道LUT对细菌病原体的抗菌活性，然而，LUT介导的基本抗菌机制从未得到阐明。本研究旨在研究LUT对金黄色葡萄球菌和单核细胞增生李斯特菌的抗菌活性及其作用方式，包括浮游细胞和生物膜形式。在这里，采用肉汤微量稀释法测定了LUT对金黄色葡萄球菌和单核细胞增生李斯特菌的最低抑菌浓度（MIC）和最低杀菌浓度（MBC），并通过评估细胞膜完整性和细胞形态的变化来阐明LUT的抗菌模式。此外，通过结晶紫染色法测定生物膜抑制作用，同时通过共聚焦激光扫描显微镜和场发射扫描电子显微镜对其进行定性成像。LUT对金黄色葡萄球菌的MIC和MBC值分别为16 - 32μg/mL和32 - 64μg/mL，对单核细胞增生李斯特菌的MIC和MBC值分别为32 - 64μg/mL和64 - 128μg/mL。LUT破坏了细胞膜的完整性，表现为非存活细胞数量显著增加以及细胞形态出现明显变化。此外，LUT对生物膜形成具有强大的抑制作用，可以增强抗生素在生物膜内的扩散，并有效地杀死单菌种和双菌种生物膜细胞。总体而言，LUT对浮游细胞和生物膜细胞以及生物膜形成均具有强大的抗菌特性，因此具有作为天然食品防腐剂应用于食品中的潜力。
