Predominance of modern Mycobacterium tuberculosis isolates in North India.

Although India accounts for the highest tuberculosis (TB) burden in the world, the diversity in prevalent Mycobacterium tuberculosis strains is very poorly documented. Tuberculosis specific deletion 1 (TbD1) is a marker that has been used to differentiate ancient from modern strains. We report for the first time TbD1-based diversity in clinical M. tuberculosis isolates circulating in the North Indian states of Himachal Pradesh and Punjab. The present study documents a very high prevalence of modern strains in North India, which is in contrast to earlier studies that emphasised the predominance of ancestral strains for the majority of TB cases in India.