Evolution and emergence of multidrug-resistant Mycobacterium tuberculosis in Chisinau, Moldova

Abstract

1.ABSTRACTBackgroundDrug-resistant tuberculosis is a high priority threat to global public health. There are still critical gaps in understanding how novel drug-resistant M. tuberculosis strains emerge and, once emergent, what drives the differential propagation of certain epidemiologically-successful strains over others. This study sought to describe the joint evolutionary and epidemiological histories of a novel multidrug-resistant M. tuberculosis strain recently identified in the capital city of the Republic of Moldova (MDR Ural/4.2).MethodsUsing whole genome sequence data and Bayesian phylogenomic methods, we reconstruct the stepwise acquisition of drug-resistance mutations in the MDR Ural/4.2 strain, estimate its historical bacterial population size over time, and infer the migration history of this strain between Eastern European countries.ResultsWe infer that MDR Ural/4.2 likely evolved (via acquisition of rpoB S450L, which confers resistance to rifampin) in the early 1990s, during a period of social turmoil following Moldovan independence from the Soviet Union. This strain subsequently underwent substantial population size expansion in the early 2000s, at a time when national guidelines encouraged in hospital treatment of TB patients. We infer exportation of this strain and its INH-resistant ancestral precursor from Moldova to neighboring countries starting as early as 1985.ConclusionsOur findings underscore how public health practice and social determinants of health shape the conditions under which M. tuberculosis evolves, and demonstrates how historical changes in these conditions shape present-day challenges in TB control. These findings underscore the need for regional coordination in TB control across Eastern Europe.