Newly discovered mutations help tuberculosis to stay infectious while evolving resistance to multiple drugs.
ZUMA Press, Inc. / Alamy
A patient undergoing chest X-rays at an anti-tubercular clinic in St. Petersburg.
Bacterial 'superbugs' are getting ever more potent. Tuberculosis (TB) strains in Russia carry mutations that not only make them resistant to antibiotics but also help them to spread more effectively, according to an analysis of 1,000 genomes from different TB isolates — one of the largest whole-genome study of a single bacterial species so far.
TB, which is caused by the bacterium Mycobacterium tuberculosis, exploded in Russia and other former Soviet nations in the early 1990s, after the collapse of the Soviet Union and its health system. The incomplete antibiotic regimens some patients received, meanwhile, sparked rampant drug resistance. But the latest study of TB cases in Russia, published today in Nature Genetics1, indicates that such ‘programmatic’ failures may not be the only explanation for the rise of drug-resistant TB in the region — biological factors also play a big part.
As part of a long-standing effort to study the rampant drug-resistant TB in Samara, a region of Russia about 1,000 kilometres southeast of Moscow, researchers collected TB isolates from 2,348 patients and sequenced the entire genomes of 1,000 of them. This enabled the team to identify previously unknown mutations linked to antibiotic resistance, as well as 'compensatory mutations' that improve the ability of drug-resistant TB to spread.
Nearly half of the TB isolates were multi-drug resistant, which means that they were impervious to the two common first-line antibiotics that cure most TB infections, while 16% of these isolates also harboured mutations that made them impervious to ‘second-line’ drugs. These infections are more expensive to treat, and patients who receive ineffective drugs are more likely to spread TB.
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