MLST-Based Population Genetic Analysis in a Global Context Reveals Clonality amongst Cryptococcus neoformans var. grubii VNI Isolates from HIV Patients in Southeastern Brazil.
MLST-Based Population Genetic Analysis in a Global Context Reveals Clonality amongst Cryptococcus neoformans var. grubii VNI Isolates from HIV Patients in Southeastern Brazil.
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全球范围内基于 MLST 的群体遗传分析揭示了新型隐球菌变种之间的克隆性。 grubii VNI 从巴西东南部的 HIV 患者中分离出来。
DOI：
10.1371/journal.pntd.0005223
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发表时间：
2017-01
影响因子：
3.8
通讯作者：
Silva-Vergara ML
中科院分区：
文献类型：
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作者：
Ferreira-Paim K;Andrade-Silva L;Fonseca FM;Ferreira TB;Mora DJ;Andrade-Silva J;Khan A;Dao A;Reis EC;Almeida MT;Maltos A;Junior VR;Trilles L;Rickerts V;Chindamporn A;Sykes JE;Cogliati M;Nielsen K;Boekhout T;Fisher M;Kwon-Chung J;Engelthaler DM;Lazéra M;Meyer W;Silva-Vergara ML
隐球菌病是一种重要的真菌感染的免疫功能低下的个人，特别是那些感染了艾滋病毒。在巴西，尽管公共卫生系统免费提供抗逆转录病毒疗法，但新型隐球菌脑膜炎造成的死亡率仍然很高。为了更详细地了解该物种在巴西东南部的种群遗传结构，我们研究了来自101名患者的108株临床分离株和35株环境分离株。在这些患者中，59%的患者出现致死性结局，主要发生在HIV阳性男性患者中。所有分离株均为C.新形变种Grubii主要分子类型VNI和交配型位点α。通过流式细胞术和PCR筛选STE 20、GPA 1和PAK 1基因，12例被鉴定为二倍体，为交配型纯合子（AαAα）。使用ISHAM共识多位点序列分型（MLST）计划，13个序列类型（ST）被确定，其中一个是新描述的。从81株（75%）临床分离株中鉴定出ST 93，而从19株（54%）和10株（29%）环境分离株中分别鉴定出ST 77和ST 93。巴西东南部的菌株有一个压倒性的克隆种群结构。根据从ISHAM-MLST数据库（mlst.mycologylab.org）提取的数据，与来自不同大陆的种群进行比较时，它们表现出较少的遗传变异性。C.新形变种Grubii VNI在大约58万至480万年前从VNB分离出来。新型隐球菌/加特隐球菌物种复合体的成员是隐球菌病的病因，隐球菌病是一种危及生命的人类疾病，每年导致624，000人死亡。感染是通过吸入环境来源的脱水酵母细胞获得的。到达肺部后，真菌传播到中枢神经系统，引起脑膜脑炎。大多数HIV感染者的脑膜炎病例是由C。新生儿是一个在艾滋病毒感染率高的地区，如亚洲和非洲得到充分研究的物种。巴西也报告了类似的高流行率，但对这些感染的流行病学了解较少。我们使用MLST研究了巴西东南部地区的临床和环境分离株。结果表明，该菌具有克隆种群结构。新形变种grubii VNI，与来自不同大陆的种群相比，变异性较低。这种较低的变异性可能是最近从非洲到美洲的多次扩散事件的结果。大多数临床分离株是一种序列类型（ST 93），这也是在环境样品中发现的。通过将分析扩展到来自地球仪的分离株，有可能在C.新形变种Grubii VNI。
Cryptococcosis is an important fungal infection in immunocompromised individuals, especially those infected with HIV. In Brazil, despite the free availability of antiretroviral therapy (ART) in the public health system, the mortality rate due to Cryptococcus neoformans meningitis is still high. To obtain a more detailed picture of the population genetic structure of this species in southeast Brazil, we studied 108 clinical isolates from 101 patients and 35 environmental isolates. Among the patients, 59% had a fatal outcome mainly in HIV-positive male patients. All the isolates were found to be C. neoformans var. grubii major molecular type VNI and mating type locus alpha. Twelve were identified as diploid by flow cytometry, being homozygous (AαAα) for the mating type and by PCR screening of the STE20, GPA1, and PAK1 genes. Using the ISHAM consensus multilocus sequence typing (MLST) scheme, 13 sequence types (ST) were identified, with one being newly described. ST93 was identified from 81 (75%) of the clinical isolates, while ST77 and ST93 were identified from 19 (54%) and 10 (29%) environmental isolates, respectively. The southeastern Brazilian isolates had an overwhelming clonal population structure. When compared with populations from different continents based on data extracted from the ISHAM-MLST database (mlst.mycologylab.org) they showed less genetic variability. Two main clusters within C. neoformans var. grubii VNI were identified that diverged from VNB around 0.58 to 4.8 million years ago. The members of the Cryptococcus neoformans / Cryptococcus gattii species complex are the cause of cryptococcosis, a life-threatening human disease responsible for 624,000 deaths annually. Infection is acquired through inhalation of dehydrated yeast cells from environmental sources. After reaching the lungs, the fungus disseminates to the central nervous system causing meningoencephalitis. The majority of meningitis cases in HIV-infected patients are caused by C. neoformans, a species well studied in regions with a high prevalence of HIV infection, such as Asia and Africa. A similar high prevalence has been reported from Brazil however the epidemiology of these infections is less well understood. We studied clinical and environmental isolates from the southeast region of Brazil using MLST. The results that we obtained showed a clonal population structure of C. neoformans var. grubii VNI, with low variability when compared against populations from different continents. This lower variability is probably the result of multiple recent dispersal events from Africa to the Americas. The majority of clinical isolates were of one sequence type (ST93), which was also found in environmental samples. By expanding the analysis to isolates from around the globe, it was possible to identify two major groups among C. neoformans var. grubii VNI.