Spiez Laboratory, Federal Office for Civil Protection, Spiez, Switzerland.
Swiss National Reference Center for Francisella tularensis (NANT), Spiez, Switzerland.
Front Cell Infect Microbiol. 2018 Mar 22;8:89. doi: 10.3389/fcimb.2018.00089. eCollection 2018.
Whole genome sequencing (WGS) methods provide new possibilities in the field of molecular epidemiology. This is particularly true for monomorphic organisms where the discriminatory power of traditional methods (e.g., restriction enzyme length polymorphism typing, multi locus sequence typing etc.) is inadequate to elucidate complex disease transmission patterns, as well as resolving the phylogeny at high resolution on a micro-geographic scale. In this study, we present insights into the population structure of subsp. , the causative agent of tularemia in Switzerland. A total of 59 isolates were obtained from castor bean ticks (, animals and humans and a high resolution phylogeny was inferred using WGS methods. The majority of the population in Switzerland belongs to the west European B.11 clade and shows an extraordinary genetic diversity underlining the old evolutionary history of the pathogen in the alpine region. Moreover, a new B.11 subclade was identified which was not described so far. The combined analysis of the epidemiological data of human tularemia cases with the whole genome sequences of the 59 isolates provide evidence that ticks play a pivotal role in transmitting to humans and other vertebrates in Switzerland. This is further underlined by the correlation of disease risk estimates with climatic and ecological factors influencing the survival of ticks.
全基因组测序（WGS）方法为分子流行病学领域提供了新的可能性。对于单态生物而言，这一点尤其正确，因为传统方法（例如，限制性内切酶长度多态性分型、多位点序列分型等）的区分能力不足以阐明复杂的疾病传播模式，也无法在微观地理尺度上解析高分辨率的系统发育。在这项研究中，我们深入了解了瑞士土拉弗朗西斯菌（导致土拉热的病原体）的种群结构。从蓖麻蜱（，动物和人类）中获得了总共 59 株分离株，并使用 WGS 方法推断了高分辨率的系统发育。瑞士的大多数种群属于西欧 B.11 分支，表现出非凡的遗传多样性，突出了病原体在阿尔卑斯地区的古老进化历史。此外，还确定了一个以前未描述的新 B.11 亚分支。将人类土拉热病例的流行病学数据与 59 株分离株的全基因组序列相结合的分析结果表明，蜱在瑞士将土拉弗朗西斯菌传播给人类和其他脊椎动物方面发挥着关键作用。这进一步强调了疾病风险估计与影响蜱生存的气候和生态因素之间的相关性。
