A comprehensive analysis of tuberculosis (TB) bacterial DNA, recovered from the remains of 18th-century Europeans, reveals that mixed infections (infections with multiple strains of TB at the same time) were common, reports a study published in Nature Communications. The results also offer new insight into the evolution of TB, indicating that one of the most common lineages circulating today in Europe and the Americas (Lineage 4) originated in the Roman period.
TB was once a major killer in Europe and is experiencing resurgence in some areas; however, it is unclear how the strains and patterns of ancient infections relate to TB today. Mark Pallen and colleagues used shotgun metagenomics to analyse bacterial DNA extracted from 26 people from a crypt in the Dominican church of Vac, Hungary, most of whom had undergone natural mummification. Historical records indicate that the individuals died between 1745 and 1808. The authors were able to reconstruct 14 TB genomes from eight of the people, five of which yielded more than one genotype, indicating the prevalence of multi-strain TB infections. All of the TB genomes identified belong to Lineage 4, which still accounts for over a million TB cases a year in Europe and in the Americas. In addition, the authors found that a mother and daughter were infected with the same two bacterial strains, documenting an intimate epidemiological link between historical TB infections for the first time.