Mtb Δfcr mutants are severely impaired in developing phenotypic antibiotic tolerance under dormancy-inducing MS conditions.

Mtb-WT, its fcr gene-knockout mutants (Δfcr1 & Δfcr2) and their complemented strains (C-fcr1 & C-fcr2) were subjected to MS for up to 18 days and antibiotic tolerance of the cultures against rifampicin (5 µg/ml) and isoniazid (0.8 µg/ml) were measured as previously described [11]. Average (±SD) from three different experiments (n = 3) is shown. MS, multiple-stress.