6种食品防腐剂对金黄色葡萄球菌抑菌效果及肠毒素基因表达的影响

Inhibitory Effect of Six Food Antiseptics on the Growth and Staphylococcal Enterotoxin(SE) Gene Expression of Staphylococcus aureus

目的:探索6种食品防腐剂——亚硝酸盐、苯甲酸钠、ε-聚赖氨酸、壳聚糖、茶多酚、Nisin对1株引起食物中毒的金黄色葡萄球菌SA003的抑菌作用,以及对该菌株所含不同肠毒素基因在m RNA水平表达的影响。方法:按照GB 2760—2014《食品添加剂使用标准》限量标准的质量浓度,分别添加6种不同的防腐剂在金黄色葡萄球菌SA003初始接菌量约为105 CFU/m L的TSB液体培养基中,37℃培养24 h后进行菌落计数;同时收集菌体用于RNA提取,将提取的RNA进行反转录后,采用荧光定量聚合酶链式反应方法检测各肠毒素基因在m RNA水平上的相对表达量。结果:在国标最大限量条件下,不同添加剂对金黄色葡萄球菌SA003的抑菌作用强弱顺序分别为:Nisin>茶多酚>壳聚糖>ε-聚赖氨酸>苯甲酸钠>亚硝酸盐。6种防腐剂均能抑制肠毒素sea、sed、seg、sei、selj、selm、selr和selu基因在转录水平上的表达,但作用效果存在差异。结论:在TSB液体培养基中添加一定剂量的防腐剂不仅能抑制金黄色葡萄球菌的生长,还能够显著降低肠毒素基因的表达量。

Objective： To explore the inhibitory effect of six food antiseptics（nitrite, sodium benzoate, ε-polylysine, chitosan, polyphenols, and nisin） on the growth of Staphylococcus aureus SA003, a strain capable of causing food poisoning, as well as on the expression of enterotoxin genes by this strain at the m RNA level. Methods： According to the national standard（GB 2760—2014） concentration limits, aqueous solutions of six different preservatives were prepared and added into TSB medium inoculated with about 105 CFU/m L of S. aureus SA003. All cultures were shaken at 150 r/min at 37 ℃. After 24 h, the colonies of the cultures treated by different preservatives were counted, respectively. At the same time, the cells were collected for RNA extraction and reverse transcription. The fluorescence quantitative PCR was used to detect the relative expression level of each enterotoxin gene at the m RNA level. Results： At the GB maximum concentration limits, the inhibitory effects of different additives on the growth of S. aureus SA003 were nisin 〉polyphenols〉 chitosan〉 ε-polylysine 〉sodium benzoate 〉nitrite. All six preservatives could inhibit the expression of sea, sed, seg, sei, selj, selm, selr and selu genes at the transcriptional level and their effects were significantly different. Conclusion： Adding preservatives in liquid medium not only inhibited the growth of S. aureus, but also significantly reduced the expression of staphylococcal enterotoxin genes.