An antibiotic (or antibacterial) is a chemical compound that killsbacteria or slows their growth. They are used as medicine to treat and curediseases caused by bacteria. The first antibiotic discovered was Penicillin, a natural antibiotic produced by a fungus. Production of antibiotics first began in 1939, and in the modern day, they are made by chemical synthesis. Antibiotics can not be used to treat viruses.
Maclyn McCarty explained what it was like before antibiotics:
"There are a number of infections from which no-one had [ever] recovered before the discovery of effective anti-bacterial agents".[2]