Identifying the contribution of zinc limitation to antibiotic tolerance during S. aureus infection

摘要 金黄色葡萄球菌是导致许多慢性和复发性疾病的主要人类病原体。 感染。这些感染通常对治疗没有反应，每年导致大约2万人死亡 仅在美国。矛盾的是，在体外药敏试验中，从这些感染中分离出来的菌株经常 对注射的抗生素完全敏感，这表明宿主中存在的环境因素可能 影响金黄色葡萄球菌对抗生素的敏感性。了解这些因素是如何控制抗生素敏感性的 提高顽固性金黄色葡萄球菌感染的分辨率，减缓耐药性的演变。 我们之前已经证明，宿主内部的外部应激源，包括暴露在活性氧中 宿主先天免疫系统产生的物种(RO)无意中呈现金黄色葡萄球菌的亚群 通过抑制金黄色葡萄球菌的代谢活性来耐受抗生素的杀灭。然而，ROS暴露不能完全 解释了体内金黄色葡萄球菌的耐受状态，表明存在于 宿主降低了对金黄色葡萄球菌的抗生素效力。在这里，我们认为宿主免疫蛋白钙化保护 通过饥饿病原体锌来诱导金黄色葡萄球菌对抗生素的耐受。锌是一种重要的辅因子。 许多执行主要宿主过程的细菌金属酶的活性所需的。锌- 饥饿的金黄色葡萄球菌种群显示DNA合成、转录和 翻译，这些过程代表了杀菌抗生素作用的主要目标。主机中介 因此，锌隔离可能会无意中使金黄色葡萄球菌对抗生素的杀灭产生耐受性，这是因为它减少了 主要抗生素靶标的活性。总体而言，我们假设锌限制会导致对抗生素的耐受。 金黄色葡萄球菌在感染过程中的状态，通过饮食或免疫调节改变锌的利用率将 影响宿主内部的抗生素效力。 在AIM1中，我们将探讨靶基因失活在金黄色葡萄球菌耐药中的作用。 降低全球DNA复制和翻译率，并测量对金黄色葡萄球菌抗生素的影响 敏感度。然后我们将评估宿主介导的锌封存在诱导这一过程中的作用。 表型。在AIM2中，我们将进入金黄色葡萄球菌败血症的小鼠模型，以评估改变 生理性锌利用率(通过饮食或基因操作)以增强或抑制抗生素疗效 对抗金黄色葡萄球菌。总之，我们希望我们的发现将有助于提高我们对SA抗生素的理解 并阐明如何利用这些知识来解决目前无法解决的感染问题。

Abstract Staphylococcus aureus is a major human pathogen responsible for numerous chronic and relapsing infections. These infections often do not respond to treatment, leading to approximately 20,000 annual deaths in the US alone. Paradoxically, during in vitro susceptibility testing, isolates from these infections frequently exhibit full sensitivity to administered antibiotics, suggesting that environmental factors present in the host may influence S. aureus antibiotic susceptibility. Understanding how these factors control antibiotic susceptibility will improve the resolution of recalcitrant S. aureus infection, and slow the evolution of resistance. We have previously shown that extrinsic stressors within the host including exposure to reactive oxygen species (ROS) produced by the host innate immune system inadvertently render subpopulations of S. aureus tolerant to antibiotic killing by suppressing S. aureus metabolic activity. However, ROS exposure cannot fully account for the tolerant state of S. aureus in vivo, suggesting that other unidentified factors present within the host reduce antibiotic efficacy against S. aureus. Here we propose that the host immune protein calprotectin induces an antibiotic tolerant state in S. aureus by starving the pathogen of zinc. Zinc is an essential cofactor required for the activity of numerous bacterial metalloenzymes that carry out the major host processes. Zinc- starved populations of S. aureus demonstrate significantly reduced rates of DNA synthesis, transcription, and translation, and these processes represent the primary targets of bactericidal antibiotic action. Host-mediated zinc sequestration may therefore inadvertently render S. aureus tolerant to antibiotic killing by reducing the activity of major antibiotic targets. Overall, we hypothesize that zinc limitation induces an antibiotic tolerant state in S. aureus during infection and that altering zinc availability through diet or immune modulation will influence antibiotic efficacy within the host. In AIM1 we will probe the role of target inactivation in driving S. aureus antibiotic tolerance by directly reducing global DNA replication and translation rates, and measuring the impact on S. aureus antibiotic susceptibility. We will then assess the contribution of host-mediated zinc sequestration in inducing this phenotype. In AIM2 we will move into a mouse model of S. aureus sepsis to assess the relevance of altering physiological zinc availability (through diet or genetic manipulation) to enhance or suppress antibiotic efficacy against S. aureus. In all, we expect that our findings will help improve our understanding of SA antibiotic susceptibility, and elucidate how such knowledge can be exploited to resolve currently unresolvable infections.