美国研究人员22日公布研究报告称，一种致命隐球菌菌株正在美国西北地区以及加拿大不列颠哥伦比亚省扩散。
研究人员表示，隐球菌通常只感染器官移植者、艾滋病患者等免疫力低下人群，但在北美传播的这种新菌株与之不同。领导这项研究的杜克大学学者埃德蒙?伯恩斯表示，这种菌株令人不安，因为它似乎对其他健康人也构成威胁。
据研究人员介绍，这种菌株致死率非常高，在他们研究的20多例病例中，死亡率约为25%。1999年至2003年，这种菌株仅局限于加拿大温哥华岛，但2003年至2006年，该菌株开始向加拿大不列颠哥伦比亚省大陆地区扩散，2005年至2009年扩散至美国华盛顿州和俄勒冈州，目前还可能进一步扩散至美国加利福尼亚州北部以及更远的地方。
研究人员表示，目前感染者除人类外，还包括猫、狗、羊驼以及绵羊等动物，人畜感染这种菌株后可在两周后出现诸如持续数周的咳嗽、胸部剧痛、呼吸短促、头疼、发烧、盗汗及体重下降等症状。冷冻可以杀死这种菌株，但气候变化可促其传播。
相关研究成果已发表在美国《公共科学图书馆.病原体》杂志上。
原文出处：
PLoS Pathog doi:10.1371/journal.ppat.1000850
Emergence and Pathogenicity of Highly Virulent Cryptococcus gattii Genotypes in the Northwest United States
Edmond J. Byrnes, III1#, Wenjun Li1#, Yonathan Lewit1#, Hansong Ma2, Kerstin Voelz2, Ping Ren3, Dee A. Carter4, Vishnu Chaturvedi3, Robert J. Bildfell5, Robin C. May2, Joseph Heitman1*
1 Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America, 2 Department of Molecular Pathobiology, School of Biosciences, University of Birmingham, Birmingham, United Kingdom, 3 Mycology Laboratory, Wadsworth Center, Albany, New York, United States of America, 4 Department of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, Australia, 5 Department of Biomedical Sciences, Oregon State University, Corvallis, Oregon, United States of America
Cryptococcus gattii causes life-threatening disease in otherwise healthy hosts and to a lesser extent in immunocompromised hosts. The highest incidence for this disease is on Vancouver Island, Canada, where an outbreak is expanding into neighboring regions including mainland British Columbia and the United States. This outbreak is caused predominantly by C. gattii molecular type VGII, specifically VGIIa/major. In addition, a novel genotype, VGIIc, has emerged in Oregon and is now a major source of illness in the region. Through molecular epidemiology and population analysis of MLST and VNTR markers, we show that the VGIIc group is clonal and hypothesize it arose recently. The VGIIa/IIc outbreak lineages are sexually fertile and studies support ongoing recombination in the global VGII population. This illustrates two hallmarks of emerging outbreaks: high clonality and the emergence of novel genotypes via recombination. In macrophage and murine infections, the novel VGIIc genotype and VGIIa/major isolates from the United States are highly virulent compared to similar non-outbreak VGIIa/major-related isolates. Combined MLST-VNTR analysis distinguishes clonal expansion of the VGIIa/major outbreak genotype from related but distinguishable less-virulent genotypes isolated from other geographic regions. Our evidence documents emerging hypervirulent genotypes in the United States that may expand further and provides insight into the possible molecular and geographic origins of the outbreak.
