The efficacy of antimicrobials is an important aspect during their applications in food and therapeutics. In this study, combination of two bacteriocins, enterocin LD3 and plantaricin LD4, was studied against two pathogenic bacteria, Staphylococcus aureus subsp. aureus ATCC25923 and Salmonella enterica subsp. enterica serovar Typhimurium ATCC13311 for increasing their potency and bactericidal activity. The minimal inhibitory concentrations (MICs) of enterocin LD3 and plantaricin LD4 against Staph. aureus subsp. aureus ATCC25923 were 180 and 220 μg/mL, whereas in combination, reduced to 115 μg/mL, respectively. The MICs of enterocin LD3 and plantaricin LD4 against Salm. enterica subsp. enterica serovar Typhimurium ATCC13311 were 240 and 320 μg/mL, respectively, whereas in combination, these were found to be 130 μg/mL, respectively. The fractional inhibitory concentration (FIC) indices calculated as 0.50 against Staph. aureus subsp. aureus ATCC25923 and 0.43 against Salm. enterica subsp. enterica serovar Typhimurium ATCC13311 were found to be ≤ 0.5 indicating the synergy. The isobologram showed MIC of combined bacteriocins falls below the plotted straight line further signifies synergy. The growth response of Staph. aureus subsp. aureus ATCC25923 and Salm. enterica subsp. enterica serovar Typhimurium ATCC13311 was significantly reduced in the presence of combined bacteriocins in comparison with their individual effects. The number of dead cells was higher as a result of combined effect as compared with their independent effect evidenced by fluorescent microscopy. Transmission electron microscopy (TEM) revealed the higher disruption of cell membrane in the combined bacteriocin-treated cells as compared with alone effects. The FTIR spectra of enterocin LD3-treated cells showed alteration at ~ 1,451.82 and ~ 1,094.30/cm corresponding to nucleic acids and phospholipids suggesting its interaction with cell membrane and nucleic acids. In contrast, plantaricin LD4-treated cells did not show such alterations suggesting plantaricin LD4 may kill target cells using other mechanism. Our data suggest that different mode of action of both bacteriocins results in division of labour and may be responsible for their synergistic activity against target cells. Similarly, the synergistic effect of bacteriocins was also observed against other pathogenic bacteria such as Proteus mirabilis ATCC43071, Pseudomonas aeruginosa ATCC27853 and Escherichia coli ATCC25922. These bacteriocins, therefore, act synergistically against target pathogens and may be applied in appropriate combinations for food safety and medical applications.

抗菌剂的功效是它们在食品和治疗学中应用的一个重要方面。在这项研究中，研究了两种细菌素肠菌素 LD3 和车前草素 LD4 的组合对抗两种病原菌金黄色葡萄球菌亚种。金黄色葡萄球菌ATCC25923 和沙门氏菌肠道亚种。enterica serovar Typhimurium ATCC13311 用于增加其效力和杀菌活性。肠菌素 LD3 和植物菌素 LD4 对葡萄球菌的最小抑制浓度 (MIC) 。金黄色葡萄球菌亚种 金黄色葡萄球菌ATCC25923 分别为 180 和 220 μg/mL，而组合时分别降至 115 μg/mL。肠菌素 LD3 和植物素 LD4 对Salm的 MIC. 肠道亚种 肠道鼠伤寒沙门氏菌ATCC13311分别为240和320微克/毫升，分别，而在组合中，这些被认为是130微克/毫升，分别。分数抑制浓度 (FIC) 指数计算为针对葡萄球菌的0.50 。金黄色葡萄球菌亚种 金黄色葡萄球菌ATCC25923 和 0.43 对Salm。肠道亚种 肠道鼠伤寒沙门氏菌ATCC13311被发现是0.5≤指示的协同作用。等效线图显示组合细菌素的 MIC 低于绘制的直线进一步表明协同作用。葡萄球菌的生长反应。金黄色葡萄球菌亚种 金黄色葡萄球菌ATCC25923 和Salm. 肠道亚种 肠溶与单独作用相比，在联合细菌素的存在下，鼠伤寒杆菌 ATCC13311 血清型显着降低。与荧光显微镜证实的它们的独立效应相比，作为组合效应的结果，死细胞的数量更高。透射电子显微镜 (TEM) 显示与单独作用相比，组合细菌素处理的细胞中细胞膜的破坏程度更高。肠菌素 LD3 处理的细胞的 FTIR 光谱显示在 ~ 1,451.82 和 ~ 1,094.30/cm 处发生改变，对应于核酸和磷脂，表明其与细胞膜和核酸的相互作用。相比之下，Plantaricin LD4 处理的细胞没有表现出这种改变，这表明 Plantaricin LD4 可能使用其他机制杀死靶细胞。我们的数据表明，两种细菌素的不同作用模式会导致分工，并且可能是它们对靶细胞产生协同活性的原因。同样，也观察到细菌素对其他病原菌的协同作用，如奇异变形杆菌ATCC43071、铜绿假单胞菌ATCC27853 和大肠杆菌ATCC25922。因此，这些细菌素可协同对抗目标病原体，并可适当组合应用于食品安全和医疗应用。