CANDIDA PATHOGENESIS IN SURGERY AND TRAUMA

在美国，多达10%的住院患者发生院内感染，估计涉及200多万患者（58,000人死亡），每年花费超过45亿美元。念珠菌是院内第六大常见病原体，也是院内血液感染的第四大常见原因。在未经治疗的患者中，全身念珠菌病的死亡率为63%至85%，而在接受适当抗真菌治疗的患者中，死亡率为33%至54%。高危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株的60%至80%，白色念珠菌是毒性最强的菌种。白色念珠菌是真核生物和二倍体，不可能使用原核细菌设计的技术构建等基因突变体。然而，使用“Ura-blaster”方法，最近可以通过破坏单个基因来构建与亲本菌株不同的白色念珠菌等基因菌株；基因INT1与上皮黏附、形态发生（从酵母形态转变为菌丝形态）和毒力有关。在本研究中，研究人员利用具有良好特征的野生型和突变型白色念珠菌菌株（携带两个、一个或零个INT1拷贝）来阐明白色念珠菌粘附和形态发生的致病意义，强调在手术和创伤的临床相关小鼠模型中，口腔感染途径的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）也被用于更明确的条件，用于将白色念珠菌丝化程度（芽管、假菌丝、真菌丝的产生）与粘附程度、内化、细胞内存活、细胞旁和细胞间迁移联系起来。体外细胞培养系统的结果与体内模型的结果是相关的。工作假设是：白色念珠菌的形态转换，即从酵母菌到菌丝的转化，在白色念珠菌的粘附和侵袭中起关键作用，从而在白色念珠菌的发病机制和毒力中起关键作用。因此，总体目的是阐明粘附和形态发生在白色念珠菌发病机制中的相关性。长期目标是利用这些信息制定新的治疗方案，以降低手术患者和创伤患者与系统性念珠菌病相关的昂贵发病率和死亡率。

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.