论文总字数：17268字

摘 要

持留菌是一种应对外界不良环境的应激生存状态，由于逃逸致死抗菌药物杀伤的特性，使很多疾病都迁延不愈，反复发作，这对感染性疾病的诊治带来巨大挑战，也给人类健康带来严重威胁。而近年来发生的多起由食源性致病菌污染低a_w食品引发的食品安全事件，也让人们对低a_w食品中微生物的存在情况有了新的认识。

目前可以完全清除持留菌的抗菌药物或其他临床治疗手段在国内还没广泛研究，因此有效控制持留菌的手段还需要很长一段时间的探索。不仅如此，目前国内关于低a_w食品的安全问题研究得较少，国外虽然已有相关的研究，但尚未清楚真正与低a_w食品中微生物的存活相关的关键影响因素、低a_w食品中微生物的失活机制与存活规律，更远未提出低a_w食品中微生物的控制方法。因此，为保证产品的安全，应了解持留菌在低水分活度环境中的存活规律及失活机制，从而选择合适的方法将其降低到可接受的水平。

通过加入氯化钠，食品中的水被结合，从而使水分活度降低。本课题拟通过微生物培养法对不同氯化钠浓度下鼠伤寒沙门氏菌进行数量变化的研究。旨在分析氯化钠对鼠伤寒沙门氏菌持留菌形成的影响。本方法可以为低a_w食品中微生物存活规律与控制的相关研究提供数据支持，对提高相关产品安全性、促进有关良性产业发展以及临床上持留菌的控制具有重要意义。结果显示：①在对数生长前期，正常培养基没有长出持留菌，其他培养基长出持留菌，随着水分活度降低，呈现先增加后减少的趋势，在4%的氯化钠LB培养基数量最多，而在对数生长前期，持留菌的形成几乎是微不足道的；②在对数生长后期，所有培养基均长出了持留菌，随着水分活度降低，呈现先增加后减少的趋势，在4%的氯化钠LB培养基数量最多。③对数生长前期存在的持留菌数量很少且变化不明显，对数生长后期持留菌数量较多且变化更明显。

关键词：持留菌 鼠伤寒沙门氏菌 低水分活度食品

Effect of low water activity environment on the formation of Salmonella persisters

Abstract

Retained bacteria is a stress state of survival of bacteria to the adverse environment. Because of the killing characteristics of escaping lethal antibacterial drugs, many diseases are prolonged and recurrent, which brings great challenges to the diagnosis and treatment of infectious diseases, and a horrible threat to the health of human beings. During this years, there have been many food safety incidents caused by low-aw food contaminated by food-borne pathogenic bacteria, which also made people have a new understanding of the existence of microorganisms in low water activity food.

At present, there are no antibiotics or other clinical treatment methods can completely eliminate retained bacteria, so it is necessary to explore effective control of retained bacteria infection for a long time. In addition, at present, there is little research on the safety of low water activity food at home and abroad, although there have been relevant studies, however, the key factors related to the survival of microorganisms in low water activity food, the inactivation mechanism and the survival rule of microorganisms in low water activity food are not clear, and the control methods of microorganisms in low water activity food are far from proposed. Therefore, in order to ensure the safety of the product, it is necessary to know the survival rule and inactivation mechanism of the retained bacteria in the low water activity environment, so as to select the appropriate method to reduce it to the acceptable level.

Sodium chloride reduces water activity by combining with water in foods. The aim of this study is to study the quantity change of sodium chloride in different concentration of sodium chloride by means of microbial culture. The aim of this study was to analyze the effects of sodium chloride on the formation of Salmonella Enterica. The method can provide data support for the study on the survival law and control of microorganisms in low water activity food, it is of great significance to improve the safety of related products, promote the development of related benign industry and control clinical retained bacteria. The results showed that: ① At the early stage of logarithmic growth, there were no retained bacteria in the normal medium and retained bacteria in the other medium. With the decrease of water activity, the number of retained bacteria increased at first and then decreased. At the early stage of logarithmic growth, the number of 4% sodium chloride LB medium was the most, the formation of persistent bacteria is almost negligible; ② at the later stage of logarithmic growth, the retained bacteria grew out of all the media, with the decrease of water activity, the first increased and then decreased, the most of them were in LB media with 4% sodium chloride. ③The number of retained bacteria in the earlier period of logarithmic growth was little and had no obvious change, but the number of retained bacteria in the later period of logarithmic growth was more and had more obvious change.

Key Words: Persisters; Salmonella typhimurium; Low water activity food

目 录

摘要 Ⅰ

Abstract II

第一章 文献综述 1

1.1 持留菌 1

1.1.1 持留菌的发现及定义 1

1.1.2 持留菌的危害 1

1.1.3 持留菌的影响因素 2

1.2 沙门氏菌 2

1.2.1 沙门氏菌及鼠伤寒沙门氏菌 2

1.2.2 沙门氏菌的危害 3

1.3 低水分活度食品 3

1.3.1 低水分活度食品引发的食品安全事件 3

1.3.2 低水分活度食品中沙门氏菌的存活规律 4

1.4 课题的选择 5

1.5 研究途径 5

第二章 实验材料及方法 6

2.1 实验试剂及材料 6

2.2 实验主要仪器 6

2.3 实验方法 6

2.3.1 不同浓度氯化钠LB培养基的制备 6

2.3.2 最低抑菌浓度（minimal inhibit concentration，MIC）的测定 7

2.3.3 生长曲线的测定 7

2.3.4 持留菌数量的测定 8

第三章 实验结果与讨论 10

3.1 活化4h后菌数量的测定 10

3.2 MIC的确定 10

3.3 对数生长期的测定 10

3.4 对数生长前期处理前、处理后0h、5h菌数量的测定 11

3.5 对数生长后期处理前、处理后0h、5h菌数量的测定 12

第四章 结论与展望 14

4.1 实验总结 14

4.2 不足与展望 14

参考文献 15

致谢 18

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