Penicillin

Penicillin is a class of antibiotic drugs—medicines that combat bacteria—originally derived from a fungus of the genus Penicillium. It was the first antibiotic to be widely used in treating bacterial infections, and its widespread use began during and after the Second World War.

Penicillin is not a single drug but a family. Members include penicillin G (usually given by injection), penicillin V (taken orally), and modified variants such as amoxicillin and ampicillin. All share a chemical structure known as the beta-lactam ring.

How it works

Penicillin inhibits the construction of the bacterial cell wall. Bacteria have a rigid wall made of a substance called peptidoglycan. Penicillin blocks the proteins that build this wall, so growing bacteria crack and die. Human cells lack this type of wall, which is why the drug causes relatively little direct harm to the body.

History

In 1928, Scottish bacteriologist Alexander Fleming observed in his London laboratory that a fungus had grown on a bacterial culture plate and stopped the bacteria from growing nearby. He named the substance 'penicillin'. Subsequently, a team at Oxford, led by Howard Florey and Ernst Chain, purified the substance in the late 1930s and 1940s and demonstrated that it worked in humans. Fleming, Florey, and Chain were awarded the Nobel Prize in Physiology or Medicine in 1945.

Uses and complications

Penicillin is used to treat many infections including streptococcal throat infection, syphilis, and some infections of the brain and lungs. Two major obstacles exist: some people have an allergy to penicillin, and drug resistance has developed. Many bacteria produce an enzyme called beta-lactamase that destroys the drug, a consequence of overuse and misuse. For this reason, penicillin is sometimes combined with drugs that inhibit this enzyme.