Whole-genome sequencing of Mycobacterium tuberculosis strains from patients in a region of Russia with high levels of drug resistant tuberculosis (TB) cases are reported this week in Nature Genetics. This large genetic survey provides insights into the emergence and evolution of drug resistant tuberculosis within a high incidence population.
Francis Drobniewski and colleagues sequenced the whole-genomes of 1,000 M. tuberculosis strains obtained from patients over a two-year period in Samara, Russia, which has a high incidence of multiple-drug resistant TB and extensively drug-resistant TB. The authors compared these strains to a diverse panel of strains isolated from patients in the United Kingdom. They examine the structure of the Russian drug resistant strains, finding that these belong to two main lineages: 642 strains belong to the Beijing lineage and 355 strains to the EuroAmerican lineage. They characterize patterns of drug resistance and drug resistance mutations, and find examples of compensatory mutations emerging in multiple-drug resistant TB strains that increase strain fitness and transmissibility.