An international consortium of researchers has traced the history of the Beijing lineage of tuberculosis. The evolution towards multi-resistant forms is closely linked to human activity.
It is the story of a bacterium and its progeny, the Beijing lineage. Since its emergence 7,000 years ago in northeast China, it has accompanied Man and the major events that have shaped his past. With him, it evolved to give rise to forms of tuberculosis increasingly resistant to antibiotic treatments.
To better understand this lineage, an international consortium of researchers, led by the Lille Infection and Immunity Center and the National Museum of Natural History (MNHN / CNRS), decided to retrace its story over the centuries. The authors of this study, published in the journal Nature, analyzed the genetic fingerprints of nearly 5,000 strains from around 100 countries. It is the largest collection of tubercle bacilli studied to date.
When war feeds the stumps
The Beijing lineage has spread to the rest of the world in successive waves, with large population movements east and west, the authors explain. But it is in contemporary times that the bacterial population has seen its numbers explode.
She thus took advantage of the most tragic events in history, such as the First World War – because tuberculosis feeds on precariousness. It has also swelled its ranks as human density has increased. As such, the industrial revolution was a tremendous opportunity for it to strengthen itself.
During the 1960s, Humans declared war on the strains of the Beijing lineage. With great reinforcements of antibiotics, it does everything to destroy its most resistant forms. With some success, since scientists note a concomitant decline phase with the appearance of these treatments.
“Russian strain”
But that was without counting on the stubbornness of these mutant bacteria. Gradually, imperceptibly, the strains of the Beijing lineage adapted to this hostile environment. Far from overcoming it, antibiotics have strengthened it. In the 1980s, multidrug resistant bacteria appeared. They are taking advantage of the emerging AIDS epidemic. The recession phase ends here.
Two strains were particularly combative. Nicknamed “Central Asian clone” and “Russian strain”, they spread after the collapse of the public health system in the former USSR. In fact, the countries of the former Soviet Union (led by Ukraine, Russia and Georgia) have one of the highest prevalence rates of tuberculosis in the world. The percentage of multidrug-resistant strains is between 10 and 30% among new cases, and 45% in patients already treated. In the region, Médecins Sans Frontières regularly sounds the alarm bells.
Using this chronology of the disease, researchers were able to identify a series of gene mutations possibly associated with epidemic spread and antibiotic resistance. “These genes are potential targets for treatment,” say the authors, who say that tuberculosis continues to kill nearly one and a half million people a year worldwide. The fight is far from won.
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