食品科学 ›› 2020, Vol. 41 ›› Issue (14): 95-101.doi: 10.7506/spkx1002-6630-20190613-149

• 生物工程 • 上一篇    下一篇

盐应激对大肠杆菌O157:H7存活和毒力基因表达的影响

余兰林,姬赛赛,禹金龙,付文静,张 林,李蛟龙,高 峰,江 芸   

  1. (1.南京农业大学动物科技学院,江苏 南京 210095;2.南京师范大学食品与制药工程学院,江苏 南京 210023)
  • 出版日期:2020-07-25 发布日期:2020-07-29
  • 基金资助:
    国家自然科学基金面上项目(31671915);江苏省“六大人才高峰”项目(NY-080)

Effects of Salt Stress on the Survival and Virulence Genes Expression of Escherichia coli O157:H7

YU Lanlin, JI Saisai, YU Jinlong, FU Wenjing, ZHANG Lin, LI Jiaolong, GAO Feng, JIANG Yun   

  1. (1. College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China;2. School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Nanjing 210023, China)
  • Online:2020-07-25 Published:2020-07-29

摘要: 探讨不同盐应激水平对大肠杆菌O157:H7存活和毒力基因表达的影响,并分析两者之间的相关性,选取本实验室收集的3 株产毒大肠杆菌O157:H7菌株(CICC21530、95和109),于不同NaCl添加量(0、6、12、18 g/100 mL)胰蛋白胨大豆肉汤中应激不同时间,进行细菌培养计数及实时聚合酶链反应检测毒力基因表达情况。结果显示,盐应激显著抑制了3 株大肠杆菌O157:H7的存活(P<0.05),抑制效应存在菌株差异,菌株CICC21530 NaCl添加量越高抑制越明显,而菌株95和109则呈现波动性变化。大肠杆菌O157:H7毒力基因表达的变化也与菌株、NaCl添加量有关。较高NaCl添加量时,3 株菌存活数显著降低的同时,毒力基因表达量却显著增加(P<0.05),其中菌株CICC21530和菌株95的18 g/100 mL NaCl处理组毒力基因表达量最高,菌株109的12 g/100 mL NaCl处理组毒力基因表达量最高。结果表明盐应激时大肠杆菌O157:H7存活与毒力基因表达的变化不完全一致,存活菌数下降的同时,毒力却会增强,提示在实际含盐食品风险评估中,不仅要关注存活菌量,还需重视残存菌的毒力水平,从而更科学全面地评估大肠杆菌O157:H7的安全风险。

关键词: 大肠杆菌O157:H7, 盐应激, 存活, 毒力基因表达

Abstract: To investigate the effects of salt stress at different levels on the survival and virulence gene expression of Escherichia coli O157:H7, as well as the correlation between them, three virulent strains (CICC21530, 95 and 109) collected in our lab were cultured separately in trypticase soy broth medium with different concentrations of NaCl (0, 6, 12 and 18 g/100 mL) for differnent time periods. Afterwards, each strain was enumarated, and the expression levels of virulence genes were detected by real-time polymerase chain reaction. Results showed that salt stress significantly decreased the survival of the three strains (P < 0.05), but the effect varied among these strains. Higher concentration of NaCl was associated with stronger inhibitory effects on strain CICC21530, while the survival of strains 95 and 109 were fluctuated. In addition, the expression levels of virulence genes in E. coli O157:H7 were related to strains and NaCl addition. At higher NaCl concentration, the expression levels of virulence genes in all strains increased significantly (P < 0.05) accompanied by a significant decrease in the survival rate. The highest expression levels of virulence genes were observed in strains CICC21530 and 95 at 18 g/100 mL NaCl concentration, and in strain 109 at 12 g/100 mL. These results suggested that the survival of E. coli O157:H7 strains were not completely consistent with the expression of virulence genes under salt stress, and the survival decreased while the expression levels of virulence genes increased. It is indicated that the survival of strains and the expression level of virulence genes should be simultaneously considered in the risk assessment of salty foods, which is beneficial for the scientific and comprehensive risk assessment of E. coli O157:H7.

Key words: Escherichia coli O157:H7, salt stress, survival, expression of virulence genes

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