Do give you an idea of the infectious nature of TB, they are also naturally resistant to some antibiotics due to them possessing a waxy outer coat in combination to their cell wall. They also divide pretty slowly adding another layer of protection. So you need specific antibiotics to get through them. As you know tb forms nodules in your lungs where it becomes somewhat dormant, a granuloma of sorts. Antibiotics resistance in TB is a real big problem too, TB is famous for being multi drug resistant in some strains.