The recent rapid expansion of multidrug resistant strains ofMycobacterium tuberculosisUral lineage 4.2 in the Republic of Moldova

Abstract

AbstractThe projected trajectory of multidrug resistant tuberculosis (MDR-TB) epidemics depends on the reproductive fitness of circulating strains of MDRM. tuberculosis (Mtb). Previous efforts to characterize the fitness of MDRMtbhave found thatMtbstrains of the Beijing sublineage (Lineage 2.2.1) may be more prone to develop resistance and retain fitness in the presence of resistance-conferring mutations than other lineages. UsingMtbgenome sequences from all culture-positive cases collected over two years in Moldova, we estimate the fitness of Ural (Lineage 4.2) and Beijing strains, the two lineages in which MDR is concentrated in the country. We estimate that the fitness of MDR Ural strains substantially exceeds that of other susceptible and MDR strains, and we identify several mutations specific to these MDR Ural strains. Our findings suggest that MDR UralMtbhas been transmitting efficiently in Moldova and poses a substantial risk of spreading further in the region.