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200多万名患者(5.8万人死亡)，每年造成的损失超过45亿美元。念珠菌是医院内第六大常见病原菌，也是引起医院血流感染的第四大常见病原体。系统性念珠菌病的死亡率在未经治疗的患者中从63%到85%不等，在接受适当抗真菌治疗的患者中从33%到54%不等。风险最高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定植栖息地，也是大多数念珠菌感染的来源。白色念珠菌占所有念珠菌分离物的60%至80%，其中白色念珠菌是最毒力的物种。白念珠菌是真核和二倍体，不可能使用为原核细菌设计的技术来构建等基因突变体。然而，使用Ura-Blaster方法，最近已经有可能通过破坏单个基因来构建与亲本菌株不同的同源白念珠菌菌株；基因INT1与上皮黏附、形态发生(从酵母菌转变为菌丝形态)和毒力有关。在这项建议中，充分表征的白念珠菌野生型和突变株(携带两个、一个或零拷贝的INT1)被用来阐明白念珠菌黏附和形态发生的致病意义，强调在临床相关的手术和创伤小鼠模型中的口腔感染途径，其中实验变量包括抗生素治疗、肠外内毒素和缺氧。相关的体外细胞培养系统(HT-29和Caco-2肠细胞)也被使用，其中可以使用更明确的条件来将白色念珠菌的丝化程度(产生芽管、假菌丝、真菌丝)与黏附、内化、细胞内存活以及细胞旁和跨细胞迁移的程度相关联。来自体外细胞培养系统的结果与来自体内模型的结果相关。工作假说是：白念珠菌的形态转换，即从酵母菌向菌丝形态的转换，在白念珠菌的黏附和入侵过程中起着关键作用，从而在白念珠菌的致病和毒力中起着关键作用。因此，总体目标是阐明黏附和形态发生在白念珠菌发病机制中的相关性。长期目标是利用这些信息来瞄准新的治疗方案，以降低外科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.