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Infect Genet Evol. 2002 Oct;2(1):39-45.

Salmonella typhi, the causative agent of typhoid fever, is approximately 50,000 years old.

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Centre for Molecular Microbiology and Infection, Imperial College of Science, Technology and Medicine, The Flowers Building, Exhibition Road, South Kensington, London SW7 2AY, UK.


A global collection of 26 isolates of Salmonella typhi was investigated by sequencing a total of 3336 bp in seven housekeeping genes. Only three polymorphic sites were found and the isolates fell into four sequence types. These results show that S. typhi is a recent clone whose last common ancestor existed so recently that multiple mutations have not yet accumulated. Based on molecular clock rates for the accumulation of synonymous polymorphisms, we estimate that the last common ancestor of S. typhi existed 15,000-150,000 years ago, during the human hunter-gatherer phase and prior to the development of agriculture and the domestication of animals.

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