Effect of inhaled Nitric Oxide on bacterial burden and disease outcome in a murine model of Klebsiella pneumonia

卫生保健相关感染是全世界的一个重要问题，并与发病率和死亡率增加有关，特别是在重症监护病房。重症监护病房中与医疗保健相关的感染有各种危险因素，包括充血性心力衰竭、肾功能障碍和免疫抑制。此外，重症监护病房的患者可能会放置侵入性设备，如气管插管或Foley导管，这进一步增加了感染的风险。气管插管的常见并发症是呼吸机相关性肺炎，这是重症监护病房最常见的获得性感染和感染死亡的主要原因。呼吸机相关性肺炎的治疗需要早期诊断和最初经验性的抗生素选择。在过去的二十年里，出现了对不同类别抗生素具有耐药性的细菌，这使得抗生素治疗变得复杂。这些所谓的多重耐药生物导致了不良的临床结果。可用于治疗这些病原体的抗生素相对较少。所谓的“最后一道防线”抗生素对多重耐药生物的效果有限，而且这些药物有明显的副作用，包括肾脏和神经毒性。理想的新型抗菌剂将具有完全不同的作用机制，从而与目前可用的抗生素具有潜在的协同效应。一氧化氮是一种气体，用于治疗新生儿肺动脉高压和心脏手术中的肺动脉高压，已被证明具有直接和间接的杀菌作用。一般来说，管理一氧化氮的成本非常高，但我的东道主的实验室建造了一个“迷你一氧化氮发生器”，它能从室内空气中产生一氧化氮。不久，这种更便宜的分娩机制将得到广泛应用，使用吸入性一氧化氮将成为治愈难治性肺炎患者的可行选择。在这个项目中，我将研究吸入性一氧化氮对肺炎克雷伯菌的影响，肺炎克雷伯菌是呼吸机相关性肺炎的常见原因。这种细菌通常会产生抗药性。我将使用体外研究来确定一氧化氮杀死肺炎克雷伯菌的最佳浓度。然后，我将确定在克雷伯氏菌肺炎小鼠模型中起作用的最佳一氧化氮浓度和给药时机。作为概念验证实验，我将进一步分析一氧化氮治疗对多重耐药肺炎克雷伯菌的影响。拟议的研究将增加我们对一氧化氮作为肺部感染辅助治疗的潜在作用的了解。预计这项研究的结果将允许一种新的方法来治疗卫生保健相关肺炎患者。

Health care-associated infections are an important problem throughout the world and are associated with increased morbidity and mortality, especially in intensive care units. There are various risk factors for health care-associated infections in the intensive care unit, including congestive heart failure, renal dysfunction and immunosuppression. In addition, patients in the intensive care unit may have invasive devices placed, such as an endotracheal tube or a Foley catheter, which further increase the risk of infection. A frequent complication of endotracheal intubation is ventilator-associated pneumonia, which is the most common acquired infection and the leading cause of death from infection in the intensive care unit. Treatment of ventilator-associated pneumonia requires early diagnosis and an initial empiric choice of antibiotics. In the last two decades, bacteria with resistance to different classes of antibiotics have emerged, which complicates antibiotic therapy. These so-called multiple drug resistant organisms contribute to adverse clinical outcomes. There are relatively few antibiotics available for the treatment of these pathogens. The so-called “last line of defense” antibiotics have a limited effect on multiple drug resistant organisms and these drugs are associated with significant side effects including nephro- and neurotoxicity. The ideal new anti-microbial agent would have a completely different mechanism of action, thereby having potential synergistic effects with currently available antibiotics. Nitric oxide, a gas which is used for the treatment of pulmonary hypertension of the newborn and pulmonary hypertension during cardiac surgery, has been shown to have direct and indirect bactericidal effect. In general the cost of administering nitric oxide is very high, but my host’s lab constructed a “mini nitric oxide generator”, which produce nitric oxide from room air. Soon, this less expensive mechanism of delivering will become widely available and use of inhaled nitric oxide will become a feasible option for the cure of patients with difficult to treat pneumonia.In this project, I will study the effect of inhaled nitric oxide on Klebsiella pneumoniae, a frequent cause of ventilator-associated pneumonia. This strain of bacteria often develops drug resistance. I will use in-vitro studies to determine the optimal concentration of nitric oxide to kill Klebsiella pneumoniae. I will then determine the optimal nitric oxide concentration and timing of nitric oxide administration to work in a murine model of Klebsiella pneumonia. As a proof-of-concept experiment, I will further analyze the effect of nitric oxide therapy on multiple drug resistance Klebsiella pneumonia. The proposed studies will increase our knowledge of the potential role of nitric oxide as an adjunctive therapy for lung infection. It is anticipated that the results of this study will permit a novel approach to treat patients with health care-associated pneumonia.