Antibiotics are chemicals. When these chemicals are put into the body they kill or stop the growth of certain kinds of germs. In other words they help your body to fight off disease.
May modern antibiotics are made from microbes, which are tiny living things. For example, bacteria and moulds are microbes. The microbes used in making antibiotics are chosen for their ability to produce chemicals that wage war on the microbes of disease. In simple terms this means that man is taking advantage of the struggle that goes on in nature among microbes.
Antibiotics are very effective at curing diseases and work in various ways. One antibiotic may act in different ways against different germs. It may kill the germs in one case and in different germs. It may kill the germs in one case and in another only weaken them and let the body’s natural defences take over.