Molecular basis for transmission of Streptococcus pyogenes

A群链球菌(Strep A)是一种高度致命的细菌，不仅可以引起简单的喉咙痛和皮肤感染，还可以引起更致命的感染，如血流感染和中毒性休克。在其他健康的人中，它是严重脓毒症的主要原因，这就是为什么它的影响往往看起来如此毁灭性。它还可以影响最近分娩的妇女，导致所谓的产床热或产后败血症；尽管非常罕见，但可悲的是，这种情况可能会导致死亡。甲型链球菌只感染人类，这意味着感染几乎总是由从另一个人那里感染细菌引起的。据信，喉咙感染是通过密切接触、一个人接触另一个人的粘液或吸入附近另一个人传播的大飞沫而感染的。皮肤感染被认为是近距离接触和触摸造成的，特别是在皮肤已经破裂的情况下。这就是为什么在处理可能受伤或最近生过孩子的脆弱人群时，洗手和清洁表面等预防措施非常重要。甲型链球菌的暴发发生在医院、托儿所、疗养院和监狱；任何可能更脆弱的人聚集在一起的地方。有时，这些疫情会继续爆发，即使在坚持洗手等预防措施的情况下，或者涉及从未亲近的人。这增加了A链可能以较小的液滴形式在空气中传播的可能性，这些液滴在空气中的停留时间可能比较大的液滴更长。猩红热是甲型链球菌引起的另一种感染，主要影响儿童，传染性很强。最近，我们调查了学校爆发的猩红热，在一些教室里发现了证据，表明空气中确实存在甲链球菌。教室里许多其他方面健康的孩子喉咙里都有同样的A型链球菌，有些人能够咳出来。这意味着一些疫情可能确实与空气传播的A链球菌有关，为了阻止这些疫情，有时可能有必要采取预防措施，以减少空气传播；仅洗手可能是不够的。预防措施可能包括改善通风，减少房间占用率和戴口罩，类似于2020年3月新冠肺炎封锁开始时所做的事情。这些干预措施对当时正在迅速增加的猩红热疫情起到了显著的抑制作用。我们认为一些类型的菌株比其他类型的菌株更善于在空气中传播。在英国，我们看到A型链霉菌出现了新的变种，在4-5年的时间里，它们已经崛起并成为主导。这表明，与较老的菌株类型相比，它们具有重大优势。类似于观察到的用来取代旧毒株类型的新冠肺炎病毒变体，我们认为优势的主要基础将是传播性。该项目旨在确定哪些甲型链球菌最适合空气传播，哪些不适合，以帮助公共卫生团队决定如何最好地应对疫情。该项目还将使用一种名为Tradis的技术，试图找出A链霉菌中的哪些基因允许它在不同的环境中生存，比如在空气中，或者在不同的表面上。这可以为细菌的不同行为提供一些洞察，并可能允许我们预测新的细菌克隆，类似于COVID19的新变种，可能会有什么行为。

Group A streptococcus (Strep A) is a highly lethal bacterium that can cause not only simple sore throats and skin infections, but also more deadly infections such as bloodstream infection and toxic shock. It is a major cause of severe sepsis in people who are otherwise healthy, which is why its effects often seem so devastating. It can also affect women who have recently given birth causing something known as childbed fever, or puerperal sepsis; although very rare, this sadly can result in deaths. Strep A only infects humans, which means that infections almost always result from catching the bacteria from another person. It is believed that throat infections are caught from close contact, by mucus from one person reaching another, or by inhaling large droplets spread from another person close by. Skin infections are believed to result from close contact and touch, particularly when the skin is already broken. This is why precautions such as handwashing, and cleaning surfaces are very important when dealing with vulnerable people who may have wounds, or have recently had a baby.Outbreaks of Strep A occur in hospitals, nurseries, care homes, and prisons; anywhere where people who might be more vulnerable are crowded together. Sometimes these outbreaks carry on, even when precautions like handwashing are being adhered to, or involve people who were never close to one another. This raises the possibility that Strep A might be transmitted in the air, in smaller droplets that can remain in the air for longer than larger droplets. Scarlet fever is another infection caused by Strep A, that mainly affects small children and is very infectious. Recently, we investigated outbreaks of scarlet fever in schools and found evidence in some classrooms that Strep A was indeed present in the air. Many of the otherwise healthy children in the classroom had the same strain of Strep A in their throats, and some were able to cough it out. This means that some outbreaks may indeed be associated with airborne Strep A, and to stop those outbreaks, it may sometimes be necessary to introduce precautions to reduce airborne spread; handwashing alone may not be sufficient. Precautions might include improved ventilation, reducing room occupancy and wearing of masks, similar to what was done at the start of the March 2020 COVID-19 lockdown. Those interventions had a dramatic dampening effect on scarlet fever outbreaks that, at the time, were increasing rapidly. We think some strain types are better at spreading in the air than others. In the UK, we have seen new variants of Strep A emerge that, over a period of 4-5 years, have risen to become dominant. This suggests they have a major advantage over older strain types. Similar to viral variants of COVID-19 that were observed to replace older strain types, we believe that the main basis for advantage will be transmissibility . This project sets out to determine which strains of strep A are most suited to airborne spread and which ones are not, to help public health teams decide how best to deal with an outbreak. The project will also use a technique knowns as TraDIS to try to work out which genes in Strep A allow it to survive in different environments such as 'air', or on different surfaces. This could provide some insight into why bacteria behave differently and might allow us to predict how new clones of bacteria, similar to new variants of COVID19, might behave.