Molecular typing of Salmonella enterica serovar Typhimurium

沙门氏菌主要引起食物中毒，是严重的人类健康问题。不同的萨蒙氏菌类型通过血清分型来识别，许多血清型都有一个名字。有2000多个血清型。最著名的血清型是鼠伤寒沙门氏菌，它是造成40%沙门氏菌感染的原因。鼠伤寒杆菌涉及感染的频率如此之高，因此有必要进一步对其进行划分，以便进行暴发调查和对该生物体的长期监测。唯一被广泛使用的对鼠伤寒杆菌进行细分的方法是噬菌体分型，这只在主要的实验室进行(澳大利亚有2个)。噬菌体分型基于一个测试分离株对一组34个噬菌体的裂解模式。噬菌体分型在追踪微生物方面发挥了关键作用，例如在英国和美国出现了一种多药耐药的新类型(DT204c)。技术很简单，但问题是，反应会随着条件的微小变化而变化，并且对反应结果进行评分是非常主观的。我们建议用基于DNA方法的分型系统来代替传统的分型系统，因此它将是简单、快速和准确的。我们将使用一种名为AFLP(扩增片段长度多态性)的DNA指纹技术来寻找特定于噬菌体类型的标记(DNA片段)，并基于我们找到的标记设计PCR分析。这样的分型系统将通过提供关于噬菌体类型的有价值的流行病学数据库的连续性来保留噬菌体分型的本质。此外，通过寻找更多的标记，分型系统可以很容易地扩展以适应任何新的类型，而当前的噬菌体分型系统很难扩展(上一次进行分型是在1977年，已经落后于我们的需求)。该项目将为设计基于分子生物学的其他病原体的分型系统建立一种通用方法，并可能对21世纪的细菌感染监测产生重大影响。

Salmonella mainly causes food poisoning and is a significant human health problem. Different Samonella forms are identified by serotyping and many serovars have been given a name . There are more than 2000 serovars. The best known serovar is Typhimurium which is the cause of 40% of salmonella infections. Typhimurium is so frequently involved in infections it is necessary to further divide it for outbreak investigations and long term monitoring of the organism. The only widely used method to subdivide Typhimurium is phage typing, which is done only in major laboratories (2 in Australia). Phage typing is based on lysis patterns of a test isolate to a set of 34 phages. Phage typing has played a crucial role in tracking the organism, for example the emergence of a multidrug resistance new type (DT204c) in UK and US. The technique is simple but the problem is that reactions vary with slight change in conditions and scoring the reaction results is very subjective. We propose to replace the typing system with one based on the DNA method PCR, so it will be simple, fast and accurate. We will use a DNA fingerprinting technique called AFLP (amplified fragment length polymorphism) to find markers (DNA segments) that are specific to phage types and design PCR assays based on the markers we find. Such a typing system will retain the essence of phage typing by providing continuity of the valuable epidemiological database on phage types. Further the typing system could easily be expanded to accommodate any new types by finding more markers while the current phage typing system is very difficult to expand (last done in 1977 and is behind in our needs). This project will establish a general approach for designing typing systems based on molecular biology for other pathogens and could have a major impact on the surveillance of bacterial infections in the 21st century.