Department of Microbiology, Faculty of Science, Prince of Songkhla University, Hat Yai, Thailand.
Excellence Research Laboratory on Natural Products, Faculty of Science, Prince of Songkla University, Hat Yai, Thailand.
Microb Drug Resist. 2019 Dec;25(10):1391-1400. doi: 10.1089/mdr.2018.0391. Epub 2019 Jul 16.
The treatment of enterococcal infections is becoming more difficult because of multidrug resistance (MDR). Lupinifolin, a prenylated flavonoid isolated from Benth., showed a potent antimicrobial activity against enterococci. The aim of this study was to investigate antibacterial activity and action of lupinifolin against MDR enterococcal clinical isolates. Antibacterial properties of lupinifolin against 21 MDR isolates were assessed using broth microdilution method and time-kill assay. To study mode of action of lupinifolin on the isolates, propidium iodide intensity, salt tolerance assay, and electron microscopic analyses were performed. Antibiofilm formation activity of lupinifolin was conducted using crytal violet assay. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration values of lupinifolin against the isolates ranged between 0.5 and 2.0 μg/mL and between 2 and 16 μg/mL, respectively. Lupinifolin at 2MIC and 4MIC inhibited the bacterial growth >2 log colony-forming units (CFU)/mL at 2 hr incubation by time-kill analysis. The compound increased membrane permeability and caused loss of salt tolerance. SEM and TEM micrographs revealed pronounced morphological and ultrastructural changes in the treated bacteria. Crystal violet staining showed the antibiofilm-producing activity of lupinifolin against four MDR enterococci. This study suggested that lupinifolin is an essential antimicrobial agent that could be useful for the treatment of MDR enterococcal infections.
由于耐多药（MDR）问题，肠球菌感染的治疗变得越来越困难。从 Benth. 中分离得到的一种被prenylated 的类黄酮 lupinifolin 对肠球菌具有很强的抗菌活性。本研究旨在研究 lupinifolin 对 MDR 肠球菌临床分离株的抗菌活性和作用机制。采用肉汤微量稀释法和时间杀伤试验评估 lupinifolin 对 21 株 MDR 分离株的抗菌特性。为了研究 lupinifolin 对分离株的作用机制，进行了碘化丙啶强度、耐盐性试验和电子显微镜分析。采用结晶紫测定法研究 lupinifolin 的抗生物膜形成活性。lupinifolin 对分离株的最小抑菌浓度（MIC）和最小杀菌浓度值范围分别为 0.5 至 2.0μg/mL 和 2 至 16μg/mL。时间杀伤分析显示，lupinifolin 在 2MIC 和 4MIC 浓度下，在 2 小时孵育时可抑制细菌生长>2 对数菌落形成单位（CFU）/mL。该化合物增加了细胞膜通透性并导致耐盐性丧失。SEM 和 TEM 显微照片显示，经处理的细菌形态和超微结构发生明显变化。结晶紫染色显示 lupinifolin 对四种 MDR 肠球菌具有抗生物膜生成活性。本研究表明，lupinifolin 是一种重要的抗菌剂，可用于治疗 MDR 肠球菌感染。
