Whole genome analysis of Mycobacterium tuberculosis isolates from recurrent episodes of tuberculosis,Finland, 1995–2013

Recurrent tuberculosis (TB) is caused by an endogenous re-activation of the same strain of Mycobacterium tuberculosis (relapse) or exogenousinfection with a new strain (re-infection).Recurrence of TB in Finland was analysed in a population-based,19-year study,and genotyping wasused to de fine relapse and re-infection.The M.tuberculosis isolates from patients with suspected relapse were further analysed by whole genome sequencing (WGS) to determine the number and type of mutations occurring in the bacterial genome between the first and second disease episodes.