Citral that is produced in the essential oils of plants is an isomeric mixture of geranial and neral. Few recent studies exhibited robust antibacterial activity of citral against several pathogens. However, little is reported about effects of citral on carbapenem-resistant Enterobacter cloacae (CREC). The purpose of this study was to assess antibacterial and antibiofilm activities of citral against CREC. Here, minimum inhibitory concentrations (MICs) of citral against CREC were determined by the agar dilution method. Antibacterial mode of citral against CREC was elucidated by evaluating changes in intracellular adenosine triphosphate (ATP) concentration, intracellular pH (pH_in), membrane potential, membrane integrity, and cell morphology. In addition, CREC cell damage within biofilms was examined by confocal laser scanning microscopy (CLSM). The results showed that the MIC of citral against CREC was 1000 μg/mL. Citral inhibited CREC growth and destroyed its cell membrane integrity, as measured by the decrease of intracellular ATP, pH, and membrane potential as well as distinctive deformation in cellular morphology. CLSM images demonstrated that citral could inactivate CREC cells within biofilms. These results revealed that citral exhibits potent antibacterial and antibiofilm activity against CREC, and thus has potential to be used as natural food preservatives to control CREC-associated infection spread.

中文翻译：

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柠檬醛对耐碳青霉烯的阴沟肠杆菌的抗菌和抗生物膜活性。

在植物精油中产生的柠檬醛是香叶和橙花的异构混合物。最近的研究很少显示柠檬醛对几种病原体的强大抗菌活性。然而，关于柠檬醛对耐碳青霉烯的阴沟肠杆菌（CREC）影响的报道很少。本研究的目的是评估柠檬醛对 CREC 的抗菌和抗生物膜活性。在这里，柠檬醛对 CREC 的最小抑制浓度 (MIC) 是通过琼脂稀释方法确定的。通过评估细胞内三磷酸腺苷 (ATP) 浓度、细胞内 pH (pH _in)、膜电位、膜完整性和细胞形态。此外，通过共聚焦激光扫描显微镜 (CLSM) 检查生物膜内的 CREC 细胞损伤。结果表明柠檬醛对CREC的MIC为1000 μg/mL。柠檬醛抑制 CREC 生长并破坏其细胞膜完整性，这是通过细胞内 ATP、pH 和膜电位的降低以及细胞形态的独特变形来衡量的。CLSM 图像表明柠檬醛可以灭活生物膜内的 CREC 细胞。这些结果表明柠檬醛对 CREC 表现出有效的抗菌和抗生物膜活性，因此有可能用作天然食品防腐剂来控制 CREC 相关的感染传播。