Critical Factors Influencing Echinocandin Resistance in Candidaglabrata

侵袭性真菌感染是全球发病率和死亡率的主要原因，占全球发病率和死亡率的近1.4 每年有100万人死亡血流真菌感染，主要是由念珠菌属的酵母菌引起的， 与高死亡率（45-75%）相关并对免疫功能低下的个体构成严重威胁， 包括癌症患者、器官移植接受者、早产儿和艾滋病患者。棘白菌素 2001年首次批准用于临床的抗真菌药物是我们有限的抗真菌药物设备的重要组成部分 并且对念珠菌属物种具有广泛的活性。这些药物阻断真菌葡聚糖合成酶， 催化β-1，3葡聚糖的生物合成，β-1，3葡聚糖是真菌细胞壁的主要结构组分。白菌素 导致临床失败的抗性是由于基因FKS 1和FKS 2的“热点”区域的突变而产生的， 其编码β-1，3葡聚糖合酶亚基。而大多数念珠菌属（Candida spp.）一直表现出较低的 棘白菌素耐药的频率（1-3%），光滑念珠菌是个例外，一些移植 中心报告C.光滑棘白菌素耐药率为10- 15%。对棘白菌素的耐药性 随着越来越多的患者暴露于抗真菌药物， 预防和棘白菌素类药物成为通用药物。此外，C.光滑的发病率一直是 目前已成为继C.北美的白色念珠菌， 欧洲因此，迫切需要更好地了解导致 棘白菌素抗性;光滑的这一建议的核心是基于最近研究的假设， 我们的实验室和其他人发表的研究表明，耐药性的出现之前有两个阶段：耐受， 多种细胞因子稳定C. glabrata在药物暴露，逃逸，其中棘白菌素耐药 FKS突变在耐药细胞中发生。我们建议找出造成这两种情况的因素 通过以下补充方法分阶段进行：（1）检测候选基因在药物耐受中的作用 和体外抗性（逃逸）的发展，并在体内验证它们，以及（2）鉴定遗传 多态性影响药物耐受性和逃逸在我们广泛收集的C.光滑临床分离株 来自美国和地球仪不同地理位置的菌株（约1000株）。对于每种方法， 我们将利用我们定义明确的体外试验和最近开发的临床相关胃肠道 定植和腹腔内脓肿模型，模拟人类耐药性的出现。所有这些 方法将定义重要真菌病原体的潜在生物学的关键特征， 这些靶点可以提高治疗成功率并防止耐药性的发展。此外，委员会认为， 了解临床耐药和耐药的决定因素。glabrata菌株将导致潜在的 诊断分析，以跟踪高威胁菌株的分子流行病学。

Invasive fungal infections are a major cause of global morbidity and mortality, accounting for nearly 1.4 million deaths a year. Bloodstream fungal infections, largely caused by yeasts of the Candida genus, are associated with high mortality rates (45-75%) and pose a serious threat to immunocompromised individuals, including cancer patients, organ transplant recipients, premature infants, and AIDS patients. The echinocandin drugs, first approved for clinical use in 2001, are an essential part of our limited antifungal drug armamentarium and are broadly active against Candida species. These drugs block fungal glucan synthase, an enzyme catalysing the biosynthesis of β-1,3 glucan, a major structural component of the fungal cell wall. Echinocandin resistance resulting in clinical failures arises due to mutations in the “hot spot” regions of genes FKS1 and FKS2, which encode β-1,3 glucans synthase subunits. While most Candida spp. have shown a consistently low frequency of echinocandin resistance (1-3%), Candida glabrata has been an exception, with some transplant centers reporting C. glabrata echinocandin resistance rates of 10-15%. Echinocandin resistance always arises during therapy and is expected to increase further, as expanding numbers of patients are exposed to antifungal prophylaxis and echinocandin class drugs become generic. Furthermore, C. glabrata incidence has been increasing and it now is the second most prevalent fungal pathogen after C. albicans in North America and Europe. Thus, there is an urgent need to better understand the factors that contribute to emergence of echinocandin resistance in C. glabrata. This proposal centers around the hypothesis, based on recent studies published by our lab and others, that emergence of resistance is preceded by two stages: tolerance, where multiple cellular factors stabilize C. glabrata during drug exposure, and escape, where echinocandin-resistant fks mutations develop in the drug-tolerant cells. We propose to identify factors contributing to both of these stages by the following complementary approaches: (1) testing the roles of candidate genes in drug tolerance and development of resistance (escape) in vitro and validating them in vivo, and (2) identifying genetic polymorphisms that influence drug tolerance and escape in our extensive collection of C. glabrata clinical isolates (~1000 strains) derived from diverse geographical locations in the U.S. and around the globe. For each approach, we will utilize our well-defined in vitro assays and recently developed clinically-relevant gastrointestinal colonization and intraabdominal abscess models that mimic resistance emergence in humans. Together, these approaches will define critical features of the underlying biology of an important fungal pathogen and identify targets that can improve therapeutic success and prevent development of resistance. Furthermore, understanding determinants of tolerance and resistance in clinical C. glabrata strains will lead to potential diagnostic assays to track the molecular epidemiology of high-threat strains.