The journal Nature reported that drug-resistant TB strains in Russia are not only resistant to antibiotics, but also are able to spread more effectively. In a study of TB genomes in Samara, Russia, researchers, including Francis Drobniewski, a microbiologist at Queen Mary University in London, England, used TB isolates from 2,348 patients and conducted whole-genome sequencing on 1,000 of them. The researchers identified mutations linked to antibiotic resistance, and “compensatory mutations” that improved the ability of drug-resistant TB to spread. Approximately half of the TB isolates were multidrug-resistant (resistant to the two first-line anti-TB drugs) and 16 percent of the isolates contained mutations that made them also resistant to second-line drugs.
In addition to resisting antibiotics by blocking essential functions in bacteria such as making proteins or building cell walls, drug-resistant strains develop mutations that make bacteria divide more slowly. In this study, the bacteria had developed compensatory mutations that restore the ability to divide quickly. The researchers found these mutations in more than 400 drug-resistant isolates that were resistant to rifampicin, a first-line anti-TB drug.
Christopher Dye, an epidemiologist with the World Health Organization, noted that public-health officials still can control these strains by correctly identifying the patient’s strain and treating it with the most effective drug regimens, thus reducing the number of resistant cases. He stated that this method worked in Estonia, Hong Kong, the United States, and elsewhere.
The full report, “Evolution and Transmission of Drug-Resistant Tuberculosis in a Russian Population,” was published online in the journal Nature Genetics (2014; doi:10.1038/ng.2878).