食源性金黄色葡萄球菌肠毒素基因的分布与时序性表达

Distribution and Temporal Expression of Staphylococcus aureus Enterotoxin Genes in Foodborne Staphylococcus aureus Strains

【目的】研究食源性金黄色葡萄球菌各血清型肠毒素基因的分布,并进一步分析其时序性表达规律。【方法】针对51株各类食品中分离的金黄色葡萄球菌菌株,应用PCR技术对11种葡萄球菌肠毒素进行基因分型;提取细菌总RNA,以ftsZ和ropB作为内标基因,使用反转录荧光定量PCR研究各肠毒素基因在细菌生长周期中的表达水平变化。【结果】除see、ses和set外,其余8种肠毒素基因在51株食源性金黄色葡萄球菌菌株中均有检出,且sei和seg的检出率最高(27.45%)。各肠毒素基因在mRNA水平的时序性表达规律基本一致,均在对数后期达到峰值,随后快速下降。以内标基因为参照,同一菌株中不同肠毒素基因的相对表达量以及不同菌株中同一肠毒素基因的相对表达量均差异较大。【结论】本文系统研究了肠毒素基因在食源性金黄色葡萄球菌中的分布,并探究了肠毒素基因的时序性表达规律,对金黄色葡萄球菌毒力机制研究与食品质量安全控制具有参考意义。

[Objective] The objective of this study is to investigate the distribution of different serum enterotoxins in food-borne Staphylococcus aureus and to further analyze their temporal expression of mRNA. [Method] Fifty-one foodborne S. aureus isolates were separated, and the presence of 11 staphylococcal enterotoxins was identified by PCR technology. After the total RNA was extracted, the expression of enterotoxin mRNAs during the cell cycle were assayed in selected isolates by reverse transcriptional real-time PCR with internal control genes ftsZ and ropB. [Result] Eight SE genes were detected in the 51 food-borne S. aureus isolates. The most prevalent SE genes were seg and sei. During the growth cycle, the patterns of SE mRNA gene expression were similar in all of the selected isolates. The enterotoxin mRNAs were peaked in the post-exponential growth phase and then rapidly decreased. However, the relative expression level of different enterotoxin genes in the same isolate was different, and the same SE gene＇s expression level also varied among strains. [Conclusion] The distribution and temporal expression of foodborne enterotoxin genes were studied, which would be valuable to the study of staphylococcal food poisoning （SPF） mechanism and the control of food safety.