Super Bugs
Part of the problem is that when people are prescribed anti biotics they take them until they feel better and stop. By not doing the entire course of anti biotics they don't kill all the infection and end up breeding resistant bacteria. Another problem is taking anti biotics for viruses like colds, viruses are not effected by anti bactial medications.
The super bugs thrive well in an environment that is hostile to weaker bacteria; namely the anti biotic environment. If the super bug is left to compete with a minor, but ealier to treat bacteria it may not be able to do so if other bacteria are allowed to compete.
It should also be noted that not all bacteria are malevalent, we have pounds of bacteria in our intestines that help with digestion and even help us stay healthy. There are treatments where a doner's intestinal bacteria is transplanted into a person suffering from intestinal problems; a creepy but effective treatment.
There is an interesting theory that there is a kind of negotiation between a bacterium and the host body that eventually reduces the harm of the bacterium; a process that takes generations. An example is measels, Europeans had immunity but the American natives had no defense and died by the thousands.
