Tuberculosis is caused by bacteria. To treat tuberculosis, you kill the bacteria with specialized antibiotics. If people don't take the right amount of antibiotics, it can cause drug resistant bacteria.
Let's say you get tuberculosis. You go to your doctor, and they prescribe ten days worth of antibiotics. But after nine days, you feel ok, and stop taking the medication. What can happen is that by the ninth day, you end up killing all but 1% of the tuberculosis causing bacteria. That last 1% was close to dieing off, but it barely survived. Since that last 1% survived, thanks to the laws of "natural selection" when they repopulate (since they all survived that batch of antibiotics), all of their children will possess the resistance to that batch of antibiotics, and this trait will get stronger with each generation.
And that's what causes drug resistant bacteria (and therefor : Extensively Drug-Resistant Tuberculosis). Incidentally, if you're using anti-bacterial soap, you really should stop. That .01% of bacteria that survive probably won't be good for humanity in the long run.