An estimated 1.8 billion people worldwide have a latent tuberculosis infection LTBI , with wide variations in LTBI rates across countries. LTBI can be due to infection with either drug sensitive or drug resistant Mycobacterium tuberculosis Mtb strains. Accurate data on the prevalence of LTBI due to multidrug resistant MDR Mtb strains are unavailable, since the strains cannot be isolated for resistance testing. ...