Penicillin: Discovery, Benefits and Resistance
First discovered in the lab in 1928, penicillin was being mass produced and advertised by 1944. This poster attached to a curbside mailbox offered advice to World War II servicemen: Penicillin cures gonorrhea in 4 hours.
Credit: National Institutes of Health

Penicillin is a member of a group of antibiotics that are widely used to treat bacterial infections. Before the introduction of antibiotics, there were no effective treatments for infections caused by bacteria, such as pneumonia, tuberculosis, gonorrhea or rheumatic fever. But the drug's accidental discovery in the late 1920s ushered in a new age of medicine.

Penicillin was hailed as a "miracle drug" that could save lives and effectively treat a variety of infectious diseases. Today, there are many natural and synthetic types of penicillin, which are used to treat a wide range of ailments. However, some strains of bacteria have become resistant to penicillin and other antibiotics, making those infections more difficult, and sometimes impossible, to treat.

Alexander Fleming, a professor of bacteriology in London, is credited with discovering penicillin in 1928. Returning from vacation, he started cleaning up his messy lab and noticed that some petri dishes containing Staphylococcus bacteria had been contaminated with a mold, Penicillium notatum, which was preventing the normal growth of the bacteria, according to Dr. Howard Markel's column for PBS NewsHour. Fleming obtained an extract from the mold, named its active agent "penicillin" and determined that the extract killed many types of harmful bacteria.

"When I woke up just after dawn on September 28, 1928, I certainly didn't plan to revolutionize all medicine by discovering the world's first antibiotic, or bacteria killer. But I guess that was exactly what I did," Fleming later wrote about his discovery.

Penicillium mold growing in a petri dish.
Penicillium mold growing in a petri dish.
Credit: Satirus/Shutterstock


Fleming's lab didn't have the resources to fully develop his discovery into a usable drug. For more than a decade, other scientists tried to purify penicillin but were unsuccessful.

Then in 1939, Howard Florey, a pathology professor at Oxford University, read Fleming's paper in the British Journal of Experimental Pathology. Florey and his colleagues were able to purify penicillin and test its effectiveness on animals before the first trial with a human. On Feb. 12, 1941, Albert Alexander received the first dose of penicillin, according to the American Chemical Society (ACS). In just a few days, the treatment began healing Alexander of a life-threatening infection. Unfortunately, Florey's team ran out of the drug before Alexander was completely healed, and he died.

A year later, enough penicillin was produced to successfully treat the next patient. Anne Miller, a patient at New Haven Hospital in Connecticut, had a miscarriage and developed an infection that led to blood poisoning. Penicillin administration cleared Miller's infection.

During World War II, penicillin was mass-produced and used to treat infections in wounded and ill soldiers. Historically, infections had killed more soldiers at war than battle injuries, Markel wrote. The discovery of penicillin decreased the death rate from bacterial pneumonia in soldiers from 18% to 1%.

In 1945, Fleming, Florey and Florey's colleague, Ernst Chain, received the Nobel Prize in physiology or medicine for their discovery of penicillin. [The 10 Noblest Nobel Prize Winners of All Time]

Penicillin is given to patients with an infection caused by bacteria. Some types of bacterial infections that may be treated with penicillin include pneumonia, strep throat, meningitis, syphilis and gonorrhea, according to the National Library of Medicine. It may also be used to prevent dental infections. As an antibiotic, penicillin kills bacteria or prevents them from growing and multiplying. The drug works by attacking enzymes that build the cell walls of bacteria.

Penicillin prevents the bacteria from synthesizing peptidoglycan, a molecule in the cell wall that provides the wall with the strength it needs to survive in the human body. The drug greatly weakens the cell wall and causes bacteria to die, allowing a person to recover from a bacterial infection.

Different kinds of penicillin are used for various infections. Some types of penicillin are amoxicillin, ampicillin, Augmentin, penicillin G and penicillin V.

Though penicillin has saved many lives, it isn't always helpful for everyone. For example, some people have penicillin allergies that can cause a rash, hives, itching, skin swelling, anaphylaxis (a life-threatening allergic reaction) and other symptoms.

Beyond allergies, penicillin is becoming less effective over time, as bacteria have become resistant to the antibiotics designed to kill them. Each year, at least 2 million people in the United States develop a bacterial infection that is resistant to antibiotics and at least 23,000 people die as a result, according to the Centers for Disease Control and Prevention (CDC).

The overuse and misuse of antibiotics contribute to the development of antibiotic resistance, according to the Mayo Clinic. Every time a person takes antibiotics, most bacteria are killed, but a few drug-resistant bacteria strains are left to grow and multiply. This means that regular antibiotic use may increase the number of drug-resistant bacteria in the body.

For this reason, antibiotics should only be used to treat bacterial infections and should not be prescribed for viral infections, such as colds, flu, most sore throats, bronchitis and many types of sinus and ear infections, according to the CDC.

Nonetheless, many sore throats and upper respiratory infections that are caused by viruses are often treated with antibiotics because it is a perceived quick fix, said Dr. Saul R. Hymes, medical director for Pediatric Antimicrobial Stewardship at Stony Brook Children's Hospital in New York.

"Overall, there is a major problem with inappropriate antibiotic prescribing in the United States," Hymes told Live Science. A 2016 studyreported that between 30% and 50% of all antibiotic prescriptions for common conditions such as ear infections, sore throats and other upper respiratory-type infections may have been inappropriate and unnecessary.

Additional Resources:

This article is for informational purposes only, and is not meant to offer medical advice. This article was updated on May 30, 2019 by Live Science contributor Cari Nierenberg.