Department of Food Science and Technology, National University of Singapore, Singapore 117542, Singapore; National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Suzhou, Jiangsu 215123, PR China.
School of Horticulture, Hainan University, Haikou, Hainan 570228, PR China.
Food Res Int. 2022 Jul;157:111241. doi: 10.1016/j.foodres.2022.111241. Epub 2022 Apr 16.
Essential oils (EOs), such as thyme (Thy) and cinnamon (Cin) oils, present promising antibacterial properties against foodborne pathogens (e.g., Salmonella enterica serovar Typhimurium). However, the food matrix might result in sublethal EO stress, and little information about direct and/or cross-resistance development after sublethal EO exposure is available. This study revealed that S. Typhimurium under sublethal Thy and Cin (50% minimum inhibitory concentration, MIC) treatments exhibited a lower growth rate and an extended lag phase. EO adapted cells showed direct-resistance to subsequent lethal EO treatment, and cross-resistance to thermal (58 °C) and oxidative (hydrogen peroxide, 50 mmol/L) stresses. Metabolomics analysis revealed changes of 47 significant metabolites (variable importance in projection > 1, false discovery rate (FDR) < 0.05), including lipids, oligopeptides, amino acids, nucleotide related compounds, and organic acids. Metabolic pathways, such as aminoacyl-tRNA biosynthesis, were shown to be involved in EO adaptation. Furthermore, a transcriptomics study identified 161 differentially expressed genes (DEGs, fold change > 2, FDR < 0.05) in MIC Thy treated cells, while more DEGs (324) were screened from the MIC Cin group. The integrated omics analysis allowed us to speculate on the molecular mechanisms. Under harsher Thy stress, S. Typhimurium cells adopted a conservative strategy to survive. By contrast, more radical responses were observed during Cin adaptation. In conclusion, the food industry should be more cautious in the use of EOs because sublethal EO stress might result in the development of resistance.
精油（EOs），如百里香（Thy）和肉桂（Cin）油，具有对抗食源性病原体（例如肠炎沙门氏菌血清型 Typhimurium）的有前景的抗菌特性。然而，食物基质可能导致亚致死 EO 应激，并且关于亚致死 EO 暴露后直接和/或交叉抗性发展的信息很少。本研究表明，亚致死 Thy 和 Cin（最低抑菌浓度的 50%，MIC）处理下的鼠伤寒沙门氏菌表现出较低的生长速率和延长的迟滞期。适应 EO 的细胞对随后的致死 EO 处理表现出直接抗性，并且对热（58°C）和氧化（过氧化氢，50mmol/L）应激表现出交叉抗性。代谢组学分析显示 47 种显著代谢物（投影变量重要性 > 1，错误发现率（FDR）< 0.05）发生变化，包括脂质、寡肽、氨基酸、核苷酸相关化合物和有机酸。氨基酸酰基-tRNA 生物合成等代谢途径被证明与 EO 适应有关。此外，MIC Thy 处理细胞的转录组学研究鉴定了 161 个差异表达基因（DEGs，倍数变化 > 2，FDR < 0.05），而 MIC Cin 组筛选出更多的 DEGs（324）。综合组学分析使我们能够推测分子机制。在更苛刻的 Thy 应激下，鼠伤寒沙门氏菌细胞采用保守策略存活。相比之下，在 Cin 适应过程中观察到更多的激进反应。总之，食品行业在使用 EOs 时应更加谨慎，因为亚致死 EO 应激可能导致抗性的发展。
