Penicillin was the first antibiotic to be discovered by Alexander Fleming (1928). He found that fungus Penicillium notatum or its extract could inhibit the growth of bacterium Staphylococcus aureus. However, its full potential as an effective antibiotic was established much later by Ernst Chain and Howard Florey. This antibiotic was extensively used to treat American soldiers wounded in the World War II. Fleming, Chain and Florey were awarded the Nobel prize in 1945, for this discovery.