Research press release


Nature Genetics

Global genetic survey of the typhoid fever agent

腸チフスの病原体であるチフス菌(Salmonella enterica Typhi)の19種の菌株について実施された全ゲノム比較研究の成果が、Nature Genetics(電子版)に掲載される論文で報告される。今回の研究は、1つのヒト病原体を概観した研究として、これまでで最も網羅的で、年間約1700万人に影響を与えるチフス菌の多様性と進化に関して新たな知見をもたらしている。

今回の研究が行われるまでは、チフス菌の全ゲノム塩基配列は、2種の菌株についてのみ報告されていた。今回、ウェルカムトラスト・サンガー研究所(英国ヒンクストン)のK Holtらの研究チームは、新しいハイスループット塩基配列解読技術を用い、それぞれ進化の過程の異なる17種の菌株を加えて、全ゲノム塩基配列を解読し、チフス菌の遺伝的多様性を可能な限り広範な観点から検討した。



A whole-genome comparison of 19 strains of Salmonella enterica Typhi, the causative agent of typhoid fever, is presented in a study published online this week in Nature Genetics. It is the most comprehensive overview to date of a human disease causing agent, and provides new insight into the variation and evolution of an agent that affects approximately 17 million people annually.

Prior to this study, complete genome sequences were available for two strains of Typhi. Kathryn Holt and colleagues used new high-throughput sequencing technologies to generate whole-genome sequences for an additional 17 strains with different evolutionary histories, therefore allowing the broadest possible view of genetic variation in Typhi.

A comparison of these genomes shows that there is relatively little variation between strains, and that most seem to be evolving as a consequence of loss of gene function. The limited amount of variation present implies that the agents that cause the disease are not under strong selective pressure from the human immune system, possibly residing in sites that are not targeted by the immune response.

The observation of relatively invariant Typhi genomes is also consistent with the idea that human carriers of the disease that display no symptoms provide the main mode of transmission of Typhi, as persistence in the environment would presumably allow for the sort of exchanges that promote genetic diversity. The study therefore supports the idea that vaccination to reduce the number of carriers in the population is a key long-term strategy for disease control.

doi: 10.1038/ng.195


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