The study evaluated the in vitro antimicrobial and antibiofilm efficacy of an antimicrobial peptide (AMP), lactoferricin (17–30) [Lfcin (17–30)], against biofilm-forming multi-drug-resistant (MDR) strains of enteroaggregative Escherichia coli (EAEC), and subsequently, the in vivo antimicrobial efficacy was assessed in a Galleria mellonella larval model. Initially, minimum inhibitory concentration (MIC; 32 μM), minimum bactericidal concentration (MBC; 32 μM), and minimum biofilm eradication concentration (MBEC; 32 μM) of Lfcin (17–30) were determined against MDR-EAEC field isolates (n = 3). Lfcin (17–30) was tested stable against high-end temperatures (70 and 90°C), physiological concentration of cationic salts (150 mM NaCl and 2 mM MgCl₂), and proteases (proteinase-K and lysozyme). Further, at lower MIC, Lfcin (17–30) proved to be safe for sheep RBCs, secondary cell lines (HEp-2 and RAW 264.7), and beneficial gut lactobacilli. In the in vitro time-kill assay, Lfcin (17–30) inhibited the MDR-EAEC strains 3 h post-incubation, and the antibacterial effect was due to membrane permeation of Lfcin (17–30) in the inner and outer membranes of MDR-EAEC. Furthermore, in the in vivo experiments, G. mellonella larvae treated with Lfcin (17–30) exhibited an increased survival rate, lower MDR-EAEC counts (P < 0.001), mild to moderate histopathological changes, and enhanced immunomodulatory effect and were safe to larval cells when compared with infection control. Besides, Lfcin (17–30) proved to be an effective antibiofilm agent, as it inhibited and eradicated the preformed biofilm formed by MDR-EAEC strains in a significant (P < 0.05) manner both by microtiter plate assay and live/dead bacterial quantification-based confocal microscopy. We recommend further investigation of Lfcin (17–30) in an appropriate animal model before its application in target host against MDR-EAEC strains.

该研究评估了 体外 抗菌肽（AMP）乳铁蛋白（17–30）[Lfcin（17–30）]的抗微生物和生物膜形成作用对肠聚集性生物膜形成多药耐药（MDR）菌株 大肠杆菌 （EAEC），随后 体内 抗菌功效在 梅洛内拉广场幼虫模型。最初，针对MDR-EAEC现场分离株，测定了Lfcin（17–30）的最小抑菌浓度（MIC; 32μM），最小杀菌浓度（MBC; 32μM）和最小生物膜清除浓度（MBEC; 32μM）（ñ= 3）。Lfcin（17–30）经过测试，可抵御高端温度（70和90°C），生理浓度的阳离子盐（150 mM NaCl和2 mM MgCl ₂）和蛋白酶（蛋白酶K和溶菌酶）稳定。此外，在较低的MIC下，Lfcin（17-30）被证明对绵羊RBC，次级细胞系（HEp-2和RAW 264.7）和有益的肠道乳杆菌是安全的。在里面体外经过时间杀灭试验，Lfcin（17–30）在孵育后3小时抑制了MDR-EAEC菌株，抗菌作用归因于Lfcin（17–30）在MDR-EAEC的内膜和外膜中渗透。此外，在体内 实验， G.mellonella 用Lfcin（17–30）治疗的幼虫显示出更高的存活率，降低了MDR-EAEC计数（P<0.001），轻度至中度的组织病理学变化，增强的免疫调节作用，与感染对照相比对幼虫细胞安全。此外，Lfcin（17–30）被证明是一种有效的抗生物膜剂，因为它可以显着抑制并消除由MDR-EAEC菌株形成的预先形成的生物膜。P<0.05）通过微量滴定板测定和基于活/死细菌定量的共聚焦显微镜进行观察。我们建议在将Lfcin（17-30）应用于抗MDR-EAEC菌株的目标宿主之前，在适当的动物模型中进行进一步研究。