When antibiotics were first discovered, they were seen as wonder drugs, and scientists thought that bacterial infections would not be a threat anymore. But now the over use and ability to mutate has bacteria still dangerous to our health. One reason bacteria have become resistant to antibiotics is when doctors prescribe antibiotics when it is not needed. Most mild bacterial infections your body can fight off. But if you take antibiotics for a mild infection, this puts selective pressure on the bacteria so then they must mutate to survive. And then those mutated bacteria become resistant to that antibiotic, and that mutated strain spreads to other people so when they get antibiotics to fight off that infection, then the antibiotics won't work as well. Another reason bacteria become resistant is when you don't finish your round of antibiotics. If you do not take all of the pills of antibiotics, than that leaves bacteria in the body that will live and mutate and reproduce so then that makes more bacteria that are resistant to antibiotics. These two reason cause more bacteria to become resistant, which leads to antibiotics being less effective, which leads to the developments of superbugs which are very hard to cure.