Acquisition of copper hyper-resistance is promoting increased bacterial survival in vivo.

铜具有剧毒，被人类、动物和植物防御系统用作抗菌剂，以杀死入侵的病原体。因此，所有细菌都有铜抗性机制，以中和铜毒，使其能够在体内和环境中生存。但我们已经确定了一种使细菌对铜产生超抗的机制。一些金黄色葡萄球菌已经获得了新的铜抗性机制(CopXL)。CopX是一种罕见的铜外排转运蛋白，而CopL是一种功能未知的脂蛋白。我们最新公布的数据表明，收购CopXL可以对极高水平的铜产生抵抗力，而典型的金黄色葡萄球菌不能在这种铜中生长，而且它还能提高金黄色葡萄球菌的存活率，抵御巨噬细胞的抗菌杀伤，巨噬细胞是宿主抗菌防御的一部分。这些结果表明，携带CopXL的细菌在感染期间将有更高的存活率。我们的研究表明，与CopL和CopX类似的蛋白质在环境细菌中广泛存在，表明这些基因在环境生存中具有重要但未知的功能。重要的是，它们通常不存在于致病细菌中。然而，这些基因现在正在扩散到其他几种细菌，这些细菌在人类和兽医医学中的问题越来越多。在金黄色葡萄球菌中，目前只在高毒力和可传播的群体中发现了CopXL基因，获得的和牲畜相关的甲氧西林耐药金黄色葡萄球菌(CA-，LA-MRSA)与典型的金黄色葡萄球菌相比，具有更高的传染性，它们可以在没有事先接触医疗保健环境的情况下在健康人类中引起疾病。此外，CopXL类基因正在扩散到其他几种显示出传染性增加的抗生素耐药条件致病菌，例如与医院相关的万古霉素耐药屎肠球菌、与牛乳房炎相关的甲氧西林耐药溶血葡萄球菌，以及与动物感染相关的甲氧西林耐药假中间葡萄球菌。我们的假设是，获得铜的超抗力正在推动细菌从机会性病原体进化为更毒力的菌株，不再需要依赖减弱的免疫系统来引起感染。CopXL基因携带在可移动的遗传元件上，这些遗传元件也编码对抗生素具有耐药性的基因。如果铜的超抗力通过增加对铜的杀戮的存活率来提高细菌的存活率，这将在与铜抗药性基因相同的元件上选择抗菌素耐药基因，即使在没有其他选择压力的情况下，如抗生素。这对我们对抗抗生素耐药性具有重要的意义，并进一步证明了了解铜的超抗性的必要性。我们不知道这些基因是如何赋予铜的超抗性的，也不知道获得高效的铜抗性机制对病原菌的生存和宿主对抗生素耐药性的保留的全部影响。因此，这一基础生物科学建议的目的是以金黄色葡萄球菌为模式生物，了解CopX和CopL的作用机制，以及铜超抗获得的生物学后果。为此，我们将综合运用生物化学、遗传学、微生物学以及以金黄色葡萄球菌为模型系统的体内模型：1.研究CopX和CopL的作用机制。2.确定CopX和CopL是否提高了病原菌在活体内的适合性。确定铜的超抗性对保持抗菌素耐药性的重要性。该模型系统的结果将广泛适用于金属解毒基因与抗生素耐药基因在移动遗传元件上共编码的其他系统，以及其他具有CopXL基因副本的人类感染细菌。

Copper is highly toxic and used as an antimicrobial by human, animal, and plant defence systems to kill invading pathogens. Consequently all bacteria have copper resistance mechanisms to counteract copper toxicity to enable survival in vivo and in the environment. But we have identified a mechanism that can give bacteria hyper-resistance to copper.The novel copper resistance mechanism (copXL) has been acquired by some strains of Staphylococcus aureus. CopX is an unusual copper efflux transporter, while CopL is a lipoprotein of unknown function. Our newly published data show that acquisition of CopXL confers resistance to extremely high levels of copper in which typical S. aureus cannot grow, and it promotes survival against the antibacterial killing by macrophages, which is part of the host's anti-bacterial defences. These results suggest that bacteria with copXL will have enhanced survival during infection. Our studies show that proteins similar to CopL and CopX, are widespread in environmental bacteria, indicating that these genes have an essential but unknown function in environmental survival. Importantly they are not usually found in pathogenic bacteria. However, these genes are now spreading to several other bacteria that are increasingly problematic in human and veterinary medicine. In S. aureus, the copXL genes are currently only found in the highly virulent and transmissible community acquired and livestock-associated methicillin resistant S. aureus (CA-, LA-MRSA) which have increased infectivity compared to typical S. aureus and they can cause disease in healthy humans with no prior exposure to healthcare settings. Additionally, copXL-like genes are spreading to several other antibiotic resistant opportunistic pathogens demonstrating increased infectivity, e.g. hospital associated vancomycin resistant Enterococcus faecium, methicillin resistant Staphylococcus haemolyticus associated with bovine mastitis, and methicillin resistant Staphylococcus pseudintermedius associated with animal infections. Our hypothesis is that acquisition of copper hyper-resistance is driving the evolution of bacteria from being opportunistic pathogens, to becoming more virulent strains that no longer need to rely on a weakened immune system to cause infection. The copXL genes are carried on mobile genetic elements that also encode genes for resistance to antibiotics. If copper hyper-resistance enhances bacterial survival by increasing survival against killing by copper, this will select for antimicrobial resistance genes on the same element as the copper resistance genes, even in the absence of other selective pressures such as antibiotics. This has major implications for our fight against antibiotic resistance and further justifies the need to understand copper hyper-resistance.We do not know how these genes confer copper hyper-resistance, nor understand the full implications of acquisition of highly efficient copper resistance mechanisms for pathogen survival and retention of antibiotic resistance in the host. Therefore the aim of this fundamental bioscience proposal is to use S. aureus as a model organism to understand the mechanisms of action of copX and copL, and the biological consequences of copper hyper-resistance acquisition. To do this we will use a multi-disciplinary approach involving biochemistry, genetics, microbiology, and in vivo models with S. aureus as a model system to: 1. Investigate the mechanisms of action of CopX and CopL. 2. Establish whether CopX and CopL enhance pathogen fitness in vivo.3. Determine the importance of copper hyper-resistance for retention of antimicrobial resistance.The results from this model system will be widely applicable for other systems where metal detoxification genes are co-encoded on mobile genetics elements with antibiotic resistance genes, and for other human infectious bacteria with copies of the copXL genes.