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TB Study Uncovers Latin American Clades, Molecular Features

Colombian researchers reporting in PLOS One assess Mycobacterium tuberculosis isolates collected in Latin America, focusing on representatives from a lineage called lineage 4 (L4) that was initially introduced to the Americas during European colonization. Starting with publicly available genome sequences for 866 L4 M. tuberculosis isolates collected in nine different Latin American countries, the team settled on more than 500 Central and South American isolates for a phylogenetic analysis of strains with particularly pronounced representation in the region. Together with new genome sequences and de novo assemblies for 88 M. tuberculosis isolates collected from tuberculosis patients in Medellin, Colombia, the L4 genome collection highlighted new and known clades in Latin America. In particular, the authors flagged large deletions that marked L4 sublineages, including previously unreported deletions found in strains linked to specific countries. "With this comprehensive phylogenetic analysis, we discovered modern country-specific lineages that thrive within the South American countries and that [have not] been spotted so far," they write. "Thanks to the genome assembly strategy, we characterized large genomic deletion profiles of these strains, within an evolutionary framework and report signature-like gene deletions for certain South American L4 sublineages. We also present, to date, the most comprehensive analysis of large genomic deletions in the [M. tuberculosis] L4 lineage in Latin America."