白色念珠菌菌血症病患接受fluconazole治療前與治療後之臨床菌株特性分析

Analysis on characteristics of Candida albicans from patients with persistent candidemia pre- and post- treatment of fluconazole

李楷誠(Kai-Cheng Lee)

指導教授 ： 蘇慶華

臺北醫學大學/醫學院/醫學科學研究所/碩士(2012年)

https://doi.org/10.6831/TMU.2012.00178

摘要

白色念珠菌是最常見的真菌病原菌，造成伺機性感染，嚴重時會有致死率高的瀰漫性感染，例如血流感染。目前為止，白色念珠菌尚未發現完整的有性世代，普遍認為是以絕對二倍體存在。近十幾年研究發現，白色念珠菌可以經由MTL (mating type like) 基因同型合子化後，進一步產生epigenetic的型態轉變，成為 opaque型的菌體，不同性別的opaque型可以進行二倍體之間的交配，產生四倍體的後代，隨後經由chromosome loss回到二倍體，完成擬有性世代。實驗室先前研究發現在抗真菌藥物fluconazole所產生的抑菌圈內，白色念珠菌產生顯著的微生物特徵改變，包含細胞型態劇烈改變、MTL基因同型合子化頻率提升，以及DNA content減少，本研究旨在探討上述現象是否會在臨床治療中發生。針對持續性白色念珠菌血症之患者，於fluconazole治療前與治療後都至少有一套血液培養呈陽性的個案，蒐集其治療前後的臨床菌株，目前共有來自5位患者的10株菌株。本研究首先依據臨床菌株的初始菌落形態差異，分別挑選出2~4株子代菌株，共分離出32株子代菌株。親緣性研究發現有3位患者於治療前後分別為同一親緣關係之菌株，比較其治療前後之母代與子代菌株，發現有不同的細胞形態以及性別基因型，代表同一親緣的臨床菌株之間有不同的表現型。在治療前後親緣關係不同的個案中，2位患者於給藥前的菌株皆為單一親緣關係，而在給藥後的菌株皆證實為混雜兩種品系以上之菌株，但是在同一混雜的菌株內亦發現親緣關係相近之菌株，後續值得分離更多混雜菌株之子代菌株，以釐清其親緣關係
以及fluconazole是否有改變其微生物特徵。

關鍵字

白色念珠菌 ； 念珠菌血症 ； 氟康唑 ； 分子分型

並列摘要

Candida albicans is a most prevalent, commensal and opportunistic human fungal pathogen. An invasive candida infection such as candidemia is associated with significant morbidity and mortality. For a long time, C. albicans is regarded as a diploid, apparently asexual fungus, but previous study over the past decade found a parasexual cycle to provide genetic variation. In the parasexaul cycle of C. albicans, the mating type like (MTL) gene must become homozygous, cells must epigenetic switch to opaque phase, and the opposite mating type (a/a and α/α) cells must in close proximity to mate. However, parasex is a rare phenomenon both in vitro and in vivo. Our previous study showed fluconazole in vitro treatment inhibited the growth of C. albicans and altered its microbiological characteristics, those including mating type like (MTL) homozygotes at a high frequency, morphological polymorphism, a decreased DNA content. The purpose of this study is to investigate the difference between pre- and post-fluconazole-treated clinical strains from candidemia. Five pairs of clinical C. albicans, which were each isolated from the same one patient pre- and post-treatment of fluconazole for his (her) candidemia, were collected according to the results of medical records reviews. We picked up 2~4 daughter strains by initial colony morphology of each paired strains, there are 32 daughter strains in the present study. Three of the five paired clinical strains, pre- and post-treatment of fluconazole, were found to have same phylogenetics in each paired strains and its daughter strains, other investigated microbiological characteristics including MTL type homozygotes and morphological polymorphism suggested different phenotypes in the same phylogenetic strains. In the two of different phylogenetics episodes, both were found single strain before the treatment of fluconazole, but we found different phylogenetics in the post-treatment strains. However, the mixtures of those post-treatment strains were found similar phylogenetics. It is worthy to analyze the microbiological characteristics of purified isolates by separation for
further work.

並列關鍵字

Candida albicans ； candidemia ； fluconazole ； multilocus sequence typing

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