The present invention relates to the use of a substituted quinoline derivative for the preparation of a medicament for the treatment of an infection with a drug resistant Mycobacterium strain wherein the substituted quinoline derivative is a compound according to Formula (Ia) or Formula (Ib) the pharmaceutically acceptable acid or base addition salts thereof, the stereochemically isomeric forms thereof, the tautomeric forms thereof and the N-oxide forms thereof. Also claimed is a composition comprising a pharmaceutically acceptable carrier and, as active ingredient, a therapeutically effective amount of the above compounds and one or more other antimycobacterial agents.