The drug penicillin ranks among the most important discoveries—medical or otherwise—of the 20th century. Introduced just before World War II, this “miracle drug” saved countless lives during the war by allowing doctors to prevent infections in combat wounds and to effectively control for the first time diseases like gonorrhea and syphilis. The drug was the second after sulfa, of a powerful class of medicines called antibiotics, which are now used to treat countless illnesses. Penicillin was the first bactericidal antibiotic, capable of actually killing bacteria, unlike sulfa, a bacteriostatic antibiotic that stopped their growth, allowing the body’s immune system (see Immunity, page 2) to kill them more easily.

Penicillin was discovered in 1928 by Alexander Fleming (1881–1955), a British doctor who would go on to win a Nobel Prize for the discovery in 1945. It is derived from a fungus called Penicillium, which Fleming noticed was able to kill bacteria in a petri dish. Tests showed that penicillin worked against many other disease-causing bacteria, and it was soon developed into an injectable form and later into tablet form for treating bacterial infections in humans.

In the years since penicillin’s discovery, many other fungi and microorganisms have also been found to yield antibiotics, and medications derived from those microorganisms have replaced penicillin for many uses. However, penicillins remain widely prescribed for diseases like pneumonia and meningitis.

Penicillin is not effective against viral infections such as the common cold, however, and it does not work against certain types of bacteria. Like all antibiotics, penicillin can also cause a severe and occasionally fatal allergic reaction in some people. Other side effects include skin rashes, hives, and swelling.

In addition, the overuse of antibiotics such as penicillin in today’s society has paved the way for more antibiotic-resistant pathogens, rendering the drugs ineffective at fighting a growing number of infections. Failure to finish an entire prescription of penicillin, even after symptoms have gone away, can contribute to drug resistance. A current example of such bacteria is methicillin-resistant Staphylococcus aureus (MRSA), which has developed such strong resistance that it is largely unaffected by traditional antibiotics. Ironically, it was in a dish full of this very same bacterium— long before it had developed resistance—that Fleming made the fateful discovery of penicillin’s powers in the first place.

ADDITIONAL FACTS

  1. Roughly 300 to 500 people die each year from a severe allergic reaction to penicillin, called penicillin-induced anaphylaxis.
  2. Penicillin V can make birth control pills less effective.