Antibiotics are medicines that kill bacteria or slow the growth of bacteria. They are used to cure diseases. Antibiotics do not harm people. Penicillin is a popular antibiotic. Antibiotics started to be produced in 1939. Antibiotics can not stop a virus. Antibiotics are not the same thing as antibodies. Today, people fear that bacteria will not be affected by antibiotics, because bacteria might become too strong. This can happen when antibiotics are used too much. If they are used a lot, some bacteria may get used to them and not be harmed by them. This is called resistance.