Deadly TB strain emerged in China over 6,000 years ago

Scientists have decoded the genome of tuberculosis (TB) bacterium, suggesting that a pernicious family of the strain emerged in China over 6,000 years ago.

Scientists have decoded the genome of tuberculosis (TB) bacterium, suggesting 
that a pernicious family of the strain emerged in China over 6,000 years ago 
[Credit: University of Wisconsin]

A study of nearly 5,000 samples of Mycobacterium tuberculosis from around the world shows how a lineage of the bacterium that emerged thousands of years ago in Asia has since become a global killer that is widely resistant to antibiotics.

Thierry Wirth, an evolutionary geneticist at the National Museum of Natural History in Paris and colleagues analysed 4,987 samples of the ‘Beijing lineage’ from 99 countries, fully sequencing the genomes of 110 of them and more limited stretches of DNA in the rest. Consistent with its name, the Beijing lineage emerged near north-eastern China, Nature reported.

And it did so around 6,600 years ago which coincides with archaeological evidence for the beginnings of rice farming in China’s upper Yangtze River valley, researchers found.

Several ups and downs in the prevalence of a family of TB bacterium strains that 
originated in Beijing followed major social and economic events 
[Credit: Nature Genetics]

The grouping together of people in settlements made it easier for the respiratory pathogen to spread from person to person, said Wirth.

Researchers said of all the M bacterium strains circulating today, few strike more fear in public-health officials than the Beijing lineage.

First identified in greater Beijing in the mid-1990s, this lineage now circulates throughout the world and many strains are resistant to drugs that vanquish other types of TB.

The increasing availability of antibiotics in the 1960s, meanwhile, coincides with a fall in the numbers of the bacterium. However, the lineage bounded back in the late 1980s and early 1990s, researchers said.

The study is published in the journal Nature Genetics.

Source: PTI News [January 20, 2015]