臨床新型隱球菌之分型、交配型、藥物感受性與毒力因子研究

The encapsulated budding yeast, Cryptococcus neoformans, has become a critically important opportunistic pathogen in individuals who are immunocompromised in all parts of the world. Cryptococcosis is initiated by fungal spores or cells deposited in the alveoli of the lungs and life-threatening for immunocompromised individuals when Cryptococcus cells disseminate from the lungs to major organs of the body, such as central nervous system (CNS). Cryptococcal meningitis is the most common fungal infection of the CNS in AIDS patients and the etiologic agent of 99% of these cases is Cryptococcus neoformans var. grubii /serotype A. The serotype classification is based on the agglutination reactions of the capsular polysaccharide antigens, which can be determined by using absorbed rabbit sera. The serotype A, D and the hybrid AD strains belong to C. neoformans whereas serotype B and C have been classdied as Cryptococcus gattii. C. neoformans is primarily found worldwide associated with excreta from pigeons and in tree hollows. C. gattii was primarily found in tropical and subtropical regions for years until it cause endemic outbreak in immunocompetent humans on Vancouver Island in Canada. According to molecular methods, such as URA5-RFLP, M13 PCR fingerprinting, C. neoformans and C. gattii are further classified into four molecular types for each species: VNI-VNIV and VGI-VGIV respectively. There are several virulence factor which have been explored including 37℃ growth ability, melanin production, capsule formation, phospholipase and urease, etc. In this study, we analyze the molecular types and mating type of 125 clinical isolates in Taiwan from 1999 to 2004. We also investigate the virulence factors, antifugal susceptibilities, and host response in different clinical isolates. 123 of the 125 isolates were C. neoformans serotype A while the other two were C. gattii serotype B.122 of the 123 serotype A strains belongs to VNI genotype and the remain one is VNII. Two C. gattii strains are both VGI genotype. All isolates were susceptible to antifungal drugs and exhibited mating typeα. Virulence factors expression was different among these clinical isolates. All of the clinical isolates all were urease and melanin positive. Most of them were hyperphospholipase. We further analyzed the host response to hyperphospholipase strain 59 and hypophospholipase strain 24 in cell-line model and find that 59 presented greater cell adhesion ability to lung epithelial cell A549 and induced more cytotoxicty.