“…All the data on drug activity against drug-tolerant Mtb, ranging from the most studied in vitro Wayne dormancy model [ 40 ] to the papers on the sterilization of non caseum- [ 83 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 ] and caseum-forming [ 97 , 102 , 103 ] mice, shed a new light on TB biology [ 129 , 130 ]. These and other preclinical efficacy studies have shown that the greatest difficulties in curing TB do not depend only on intracellular AR bacilli and of their mutants but, above all, on extracellular NR drug-tolerant bacilli living in the caseous tuberculomas [ 4 ], the hallmark of TB.…”