College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, 712100, China.
School of Food Science and Technology, National Engineering Research Center of Seafood, Dalian Polytechnic University, Dalian, 116304, China.
Food Microbiol. 2023 Jun;112:104241. doi: 10.1016/j.fm.2023.104241. Epub 2023 Feb 17.
Viable but nonculturable (VBNC) state bacteria are difficult to detect in the food industry due to their nonculturable nature and their recovery characteristics pose a potential threat to human health. The results of this study indicated that S. aureus was found to enter the VBNC state completely after induced by citral (1 and 2 mg/mL) for 2 h, and after induced by trans-cinnamaldehyde (0.5 and 1 mg/mL) for 1 h and 3 h, respectively. Except for VBNC state cells induced by 2 mg/mL citral, the VBNC state cells induced by the other three conditions (1 mg/mL citral, 0.5 and 1 mg/mL trans-cinnamaldehyde) were able to be resuscitated in TSB media. In the VBNC state cells induced by citral and trans-cinnamaldehyde, the ATP concentration was reduced, the hemolysin-producing ability was significantly decreased, but the intracellular ROS level was elevated. The results of heat and simulated gastric fluid experiments showed different environment resistance on VBNC state cells induced by citral and trans-cinnamaldehyde. In addition, by observing the VBNC state cells showed that irregular folds on the surface, increased electron density inside and vacuoles in the nuclear region. What's more, S. aureus was found to enter the VBNC state completely after induced by meat-based broth containing citral (1 and 2 mg/mL) for 7 h and 5 h, after induced by meat-based broth containing trans-cinnamaldehyde (0.5 and 1 mg/mL) for 8 h and 7 h. In summary, citral and trans-cinnamaldehyde can induce S. aureus into VBNC state and food industry needs to comprehensively evaluate the antibacterial capacity of these two plant-derived antimicrobial agents.
金黄色葡萄球菌在受到柠檬醛（1 和 2mg/mL）诱导 2h 后完全进入 VBNC 状态，肉桂醛（0.5 和 1mg/mL）分别诱导 1h 和 3h 后完全进入 VBNC 状态。在受到 2mg/mL 柠檬醛诱导的 VBNC 状态细胞外，除了 2mg/mL 柠檬醛诱导的 VBNC 状态细胞外，其他三种条件（1mg/mL 柠檬醛、0.5 和 1mg/mL 肉桂醛）诱导的 VBNC 状态细胞均能在 TSB 培养基中复苏。在柠檬醛和肉桂醛诱导的 VBNC 状态细胞中，ATP 浓度降低，溶血素产生能力显著降低，但细胞内 ROS 水平升高。热和模拟胃液实验结果表明，柠檬醛和肉桂醛诱导的 VBNC 状态细胞具有不同的环境抗性。此外，通过观察 VBNC 状态细胞，发现表面出现不规则褶皱，内部电子密度增加，核区出现空泡。更重要的是，金黄色葡萄球菌在含有柠檬醛（1 和 2mg/mL）的肉汤中诱导 7h 和 5h 后完全进入 VBNC 状态，在含有肉桂醛（0.5 和 1mg/mL）的肉汤中诱导 8h 和 7h 后完全进入 VBNC 状态。综上所述，柠檬醛和肉桂醛均可诱导金黄色葡萄球菌进入 VBNC 状态，食品行业需要综合评估这两种植物源抗菌剂的抗菌能力。
