CANDIDA PATHOGENESIS IN SURGERY AND TRAUMA

在美国，多达10%的住院患者发生医院感染，估计涉及超过200万患者（和58，000例死亡），并且每年花费超过45亿美元。念珠菌属是第6位最常见的医院内病原体，也是第4位最常见的医院内血流感染原因。系统性念珠菌病的死亡率在未经治疗的患者中为63%至85%，在接受适当抗真菌治疗的患者中为33%至54%。最高风险的患者包括免疫抑制患者、创伤患者和术后患者。肠道被认为是主要的殖民栖息地，和大多数念珠菌感染的来源。C.白色念珠菌占所有念珠菌分离株的60%至80%，而白色念珠菌占所有念珠菌分离株的60%至80%。白色念珠菌是最毒的种类。C.白色念珠菌是真核的和二倍体的，并且不可能使用为原核细菌设计的技术构建同基因突变体。然而，使用“Ura-blaster”方法，最近已经可以构建C.通过单个基因的破坏而与亲本菌株不同的白色念珠菌;基因INT 1与上皮粘附、形态发生（从酵母转变为菌丝形式）和毒力有关。在这个建议中，充分表征的野生型和突变株的C。白色念珠菌（携带两个、一个或零个拷贝的INT 1）用于阐明C.白色念珠菌的粘附和形态发生，强调在临床相关的手术和创伤小鼠模型中的口服感染途径，其中实验变量包括抗生素治疗、肠外内毒素和缺氧。还使用了相关的体外细胞培养系统（HT-29和Caco-2肠细胞），其中可以使用更明确的条件来关联C的程度。白念珠菌的形成（芽管、假菌丝、真菌丝的产生）与粘附、内化、细胞内存活以及细胞旁和跨细胞迁移的程度有关。体外细胞培养系统的结果与体内模型的结果相关。工作假设是：C。白色念珠菌是由酵母菌转化为菌丝体的过程，在C.白念珠菌的粘附和侵袭，从而在C.白色念珠菌致病性和毒力。因此，总的目的是澄清粘附和形态发生在C。白色念珠菌发病机制长期的目标是利用这些信息来靶向新的治疗方案，以降低手术患者和创伤患者中与系统性念珠菌病相关的昂贵的发病率和死亡率。

In the United States, as many as 10% of hospitalized patients develop a nosocomial infection, estimated to involve more than 2 million patients (and 58,000 deaths), and to cost more than $4.5 billion annually. Candida species represent the 6th most common nosocomial pathogen overall, and the 4th most common cause of nosocomial bloodstream infections. Mortality from systemic candidiasis ranges from 63% to 85% in untreated patients and from 33% to 54% in those who receive appropriate antifungal therapy. Patients at highest risk include immunosuppressed patients, trauma patients, and postsurgical patients. The intestinal tract is believed to be the major colonizing habitat, and the source of most Candida infection. C. albicans accounts for 60% to 80% of all Candida isolates and C. albicans is the most virulent species. C. albicans is eucaryotic and diploid, and it is not possible to construct isogenic mutants using techniques designed for procaryotic bacteria. However, using the "Ura-blaster" method, it has recently become possible to construct isogenic strains of C. albicans that differ from a parent strain by disruption of a single gene; the gene INT1 has been associated with epithelial adhesion, morphogenesis (switching from yeast to hyphal forms), and virulence. In this proposal, well characterized wild-type and mutant strains of C. albicans (carrying two, one, or zero copies of INT1) are used to clarify the pathogenic significance of C. albicans adherence and morphogenesis, emphasizing the oral route of infection in clinically relevant mouse models of surgery and trauma, where experimental variables include antibiotic therapy, parenteral endotoxin, and hypoxia. Relevant in vitro cell culture systems (HT-29 and Caco-2 enterocytes) are also used where more defined conditions can be used to correlate the degree of C. albicans filamentation (production of germ tubes, pseudohyphae, true hyphae) with the degree of adherence, internalization, intracellular survival, and paracellular and transcellular migration. Results from in vitro cell culture systems are correlated with results from in vivo models. The working hypothesis is: Morphologic switching in C. albicans, that is conversion from yeast to hyphal forms, plays a key role in C. albicans adherence and invasion, and thus plays a key role in C. albicans pathogenesis and virulence. Thus, the overall aim is to clarify the relevance of adhesion and morphogenesis in C. albicans pathogenesis. The long term goal is to use this information to target novel treatment regimens to decrease the costly morbidity and mortality associated with systemic candidiasis in surgical patients and trauma patients.