Characterization of Klebseilla pneumoniae T6SS nanoweapon and its role in the dissemination of antimicrobial genes and virulence factors.

我们与传染病的斗争远未结束。全球化增加了大流行的风险，抗药性微生物的崛起有可能使现有药物失效。尤其令人担忧的是，在急性呼吸道感染死亡人数最多的25个国家中，英国的呼吸道感染造成的健康负担高于其他大多数欧洲国家。令人极为关切的是，由革兰氏阴性细菌，特别是肺炎克雷伯氏菌引起的呼吸道感染日益普遍(本项目的重点)。令人担忧的是，有报告显示，仅在英国，克雷伯氏菌感染的发病率在过去五年中就增加了15%。这尤其令人担忧，因为克雷伯氏菌治疗通常建议使用经验性抗生素的高耐药率。向欧洲疾病预防和控制中心报告的肺炎克雷伯菌中，超过三分之一的菌株至少对一种抗菌素耐药，这是最常见的耐药表型，对氟喹诺酮类药物、第三代头孢菌素和氨基糖苷类药物的联合耐药。值得注意的是，在克雷伯氏菌中，就像在其他微生物中一样，抗菌素耐药基因的转移是通过不同微生物之间共享质粒进行的。流行病学研究表明，克雷伯氏菌菌株可以获得一个可移动的抗菌基因和毒力因子池，从而能够出现一种多药、超强毒力的肺炎克雷伯菌克隆，能够在健康人中造成无法治疗的感染。不出所料，由于极具抗药性的菌株，克雷伯氏菌已被英国政府、美国疾病控制和预防中心以及世界卫生组织列为“对人类健康的紧急威胁”。最近，本戈切亚实验室证明肺炎克雷伯菌使用一种纳米膜，即VI型分泌系统(T6SS)来对抗其他微生物。因此，T6SS的抗菌作用与抗菌基因和毒力因子的传播是不一致的。在这个项目中，我们的研究将揭示克雷伯氏菌如何解决遗传物质转移和T6SS活性之间的冲突。我们还将提供对克雷伯氏菌产生的T6SS组件的新见解，以将抗菌毒素输送给其他细菌，并确定克雷伯氏菌部署的毒素组合。我们还将强调T6SS和脂多糖之间迄今未知的联系，脂多糖是一种位于所有革兰氏阴性细菌表面的糖脂。更好地了解微生物之间物质转移的障碍和限制，对于预测卫生保健环境中耐药微生物的爆发是非常宝贵的，并可能导致开发新的疗法来限制这一过程。此外，我们的研究将提供克雷伯氏菌所部署的抗微生物策略的全球视野。发现新的毒素并确定其作用机制将是一个有用的抗菌靶标的金矿，制药公司可以考虑开发急需的新药来对抗多重耐药感染。

Our struggle against infectious diseases is far from over. Globalisation has increased the risk of pandemics, and the rise of antibiotic-resistant microbes threatens to render existing drugs useless. Of particular concern is the health burden of respiratory infections being the UK in the top 25 countries for deaths from acute respiratory infections, above most other European countries. Of great concern is the mounting prevalence of respiratory infections caused by Gram-negative bacteria, in particular Klebsiella pneumoniae (the focus of this project). Worryingly, there are reports showing a 15% increased in incidence of Klebsiella infections in the last five years only in the UK. This is particularly alarming given the high rates of resistance to empirical antibiotics commonly recommended for Klebsiella treatment. More than a third of the K. pneumoniae isolates reported to the European Centre for Disease Prevention and Control were resistant to at least one antimicrobial group, being the most common resistance phenotype the combined resistance to fluoroquinolones, third-generation cephalosporins and aminoglycosides. Of note, in Klebsiella, like in other microbes, the transfer of antimicrobial resistance genes occurs via sharing plasmids between different microbes. Epidemiological studies have demonstrated that Klebsiella strains have access to a mobile pool of antimicrobial genes and virulence factors, enabling the emergence of a multidrug, hypervirulent K. pneumoniae clone capable of causing untreatable infections in healthy individuals. Not surprisingly, Klebsiella has been singled out as an "urgent threat to human health" by the UK Government, the U.S. Centers for Disease Control and Prevention, and the World Health Organization due to extremely drug resistant strains. Recently, the Bengoechea laboratory has demonstrated that K. pneumoniae employs a nanowaepon, the type VI secretion system (T6SS), to antagonize other microbes. Therefore, the antimicrobial action of the T6SS is at odds with the dissemination of antimicrobial genes and virulence factors. In this project, our research will uncover how Klebsiella resolves the conflict between the transfer of genetic material and the activity of the T6SS. We will also provide new insights into the T6SS assemblies that Klebsiella produces to deliver the antimicrobial toxins to other bacteria, and identify the portfolio of toxins that Klebsiella deploys. We will also highlight a hitherto unknown connection between the T6SS and the lipopolysaccharide, a glycolipid located in the surface of all Gram-negative bacteria. A better understanding of the barriers and limitations of the transfer of material between microbes is invaluable to predict outbreaks of resistant microbes in the health care setting, and may result in developing new therapeutics to limit the process. In addition, our research will provide a global vision of the antimicrobial strategies deployed by Klebsiella. Finding new toxins and determining their mechanisms of action shall be a gold mine of usable antibacterial targets that pharmaceutical companies could consider to develop much needed new drugs against multidrug resistant infections.