Not all mutation is good

For example, some bacteria that were controllable by drugs have mutated into forms that are no longer controllable. In fact, the bacteria are dining on the drugs that were supposed to kill them. And, it looks like tuberculosis, which was prevalent when I was a kid but seemed to have disappeared in the past fifty years, is making a comeback. There re now strains of tb that we cannot cure; it caused 16,000 deaths last year.