Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Food Microbiol. 2023 Jun;112:104232. doi: 10.1016/j.fm.2023.104232. Epub 2023 Jan 25.
Chlorine treatment is the most common disinfection method in food-related environments. In addition to being simple and inexpensive, this method is very effective if used properly. However, insufficient chlorine concentrations only cause a sublethal oxidative stress in the bacterial population and may alter the growth behavior of stressed cells. In the present study, the effect of sublethal chlorine stress on the biofilm formation characteristics of Salmonella Enteritidis was evaluated. Our results demonstrated that, sublethal chlorine stress (350 ppm total chlorine) activates the biofilm (csgD, agfA, adrA and bapA) and quorum-sensing (sdiA and luxS) related genes in planktonic cells of S. Enteritidis. The higher expression of these genes illustrated that the chlorine stress induced the initiation of the biofilm formation process in S. Enteritidis. Results of the initial attachment assay confirmed this finding. In addition, the number of chlorine-stressed biofilm cells was significantly higher than non-stressed biofilm cells after 48 h incubation at 37 °C. In S. Enteritidis ATCC 13076 and S. Enteritidis KL19, the number of chlorine-stressed biofilm cells were 6.93 ± 0.48 and 7.49 ± 0.57 log CFU/cm, while the number of non-stressed biofilm cells were 5.12 ± 0.39 and 5.63 ± 0.51 log CFU/cm, respectively. These findings were confirmed by measurements of the major components of biofilm, i.e., eDNA, protein and carbohydrate. The amount of these components in 48-h biofilms was higher when the cells were initially subjected to sublethal chlorine stress. However, the up-regulation of the biofilm and quorum sensing genes was not observed in 48-h biofilm cells, indicating that the effect of chlorine stress had vanished in the subsequent generations of Salmonella. In total, these results revealed that sublethal chlorine concentrations can promote the biofilm-forming ability of S Enteritidis.
氯处理是食品相关环境中最常见的消毒方法。这种方法不仅简单且廉价，如果使用得当，效果非常显著。但是，氯浓度不足只会对细菌种群造成亚致死氧化应激，并且可能改变应激细胞的生长行为。在本研究中，评估了亚致死氯应激对肠炎沙门氏菌生物膜形成特性的影响。我们的结果表明，亚致死氯应激（总氯 350ppm）会激活肠炎沙门氏菌浮游细胞中的生物膜（csgD、agfA、adrA 和 bapA）和群体感应（sdiA 和 luxS）相关基因。这些基因的高表达表明，氯应激诱导了肠炎沙门氏菌生物膜形成过程的启动。初始附着试验的结果证实了这一发现。此外，在 37°C 孵育 48 小时后，经氯处理的生物膜细胞数量明显高于未处理的生物膜细胞。在肠炎沙门氏菌 ATCC 13076 和肠炎沙门氏菌 KL19 中，经氯处理的生物膜细胞数量分别为 6.93±0.48 和 7.49±0.57 log CFU/cm，而非经氯处理的生物膜细胞数量分别为 5.12±0.39 和 5.63±0.51 log CFU/cm。通过测量生物膜的主要成分（即 eDNA、蛋白质和碳水化合物）证实了这些发现。在最初受到亚致死氯应激的情况下，48 小时生物膜中的这些成分的量更高。然而，在 48 小时生物膜细胞中没有观察到生物膜和群体感应基因的上调，表明在随后的沙门氏菌代中，氯应激的影响已经消失。总之，这些结果表明，亚致死氯浓度可以促进肠炎沙门氏菌的生物膜形成能力。
