Abstract This study aimed to analyze the effect of carvacrol oil on biofilm formation of Enterobacter cloacae. The minimum inhibitory concentration of carvacrol oil against E. cloacae was 256 μg/mL. The biofilm formation was inhibited by carvacrol oil at sub-inhibitory concentrations of 64 and 128 μg/mL. The bacterial cell motilities and biofilm exopolysaccharide (EPS) production were both inhibited by carvacrol oil. Correlation analysis indicated that the inhibition of biofilms in mature stages was related to the decrease of EPS production. The biofilm thickness and excretion of extrapolymeric matrix were reduced by carvacrol oil, as shown by scanning electron microscopy and confocal laser scanning microscopy analyses. Transcriptional analysis showed that carvacrol oil down-regulated 24 of 29 selected genes, including curli fimbriae genes (csgABCEFG) and colonic acid polysaccharide genes (wcaABCDEFKLM, wza, wzb, wzc, gmd, manB, manC) which are required for biofilm formation of E. cloacae. In addition, different antimicrobial agents, including 1% lactic acid, 1% phenyllactic acid, and 1024 μg/mL of carvacrol oil considerably inactivated the bacterial cells in carvacrol-treated biofilms. Hence, carvacrol oil effectively inhibited biofilm formation and EPS production of E. cloacae, which is useful for further inactivating E. cloacae biofilms by other antimicrobial agents.

中文翻译：

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香芹酚油抑制阴沟肠杆菌生物膜形成和胞外多糖的产生

摘要 本研究旨在分析香芹酚油对阴沟肠杆菌生物膜形成的影响。香芹酚油对阴沟肠杆菌的最小抑制浓度为 256 μg/mL。在 64 和 128 μg/mL 的亚抑制浓度下，香芹酚油可抑制生物膜形成。香芹酚油可抑制细菌细胞运动和生物膜胞外多糖 (EPS) 的产生。相关性分析表明，成熟期生物膜的抑制与EPS产量的降低有关。香芹酚油降低了聚合物外基质的生物膜厚度和排泄，如扫描电子显微镜和共聚焦激光扫描显微镜分析所示。转录分析表明香芹酚油下调了 29 个选定基因中的 24 个，包括阴沟肠杆菌生物膜形成所需的卷曲菌毛基因（csgABCEFG）和结肠酸多糖基因（wcaABCDEFKLM、wza、wzb、wzc、gmd、manB、manC）。此外，不同的抗菌剂，包括 1% 乳酸、1% 苯基乳酸和 1024 μg/mL 香芹酚油，显着灭活了香芹酚处理过的生物膜中的细菌细胞。因此，香芹酚油有效地抑制了阴沟肠杆菌的生物膜形成和 EPS 产生，这有助于其他抗菌剂进一步灭活阴沟肠杆菌生物膜。和 1024 μg/mL 的香芹酚油显着灭活了香芹酚处理过的生物膜中的细菌细胞。因此，香芹酚油有效地抑制了阴沟肠杆菌的生物膜形成和 EPS 产生，这有助于其他抗菌剂进一步灭活阴沟肠杆菌生物膜。和 1024 μg/mL 的香芹酚油显着灭活了香芹酚处理过的生物膜中的细菌细胞。因此，香芹酚油有效地抑制了阴沟肠杆菌的生物膜形成和 EPS 产生，这有助于其他抗菌剂进一步灭活阴沟肠杆菌生物膜。