Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body. It is important that specific bacteria are treated by specific antibiotics, because an antibiotic that works on one type of bacterium may not work on another.
The use of antibiotics has greatly reduced deaths from infectious bacterial diseases. However, the emergence of strains of bacteria that are resistant to antibiotics is of great concern.
Antibiotics cannot kill viral pathogens. It is difficult to develop drugs that kill viruses without also damaging the body's tissues, because viruses live inside the body's cells.
Painkillers and other medicines are used to treat the symptoms of a disease, but they do not kill pathogens.