Penicillin’s arrival marked a turning point in medicine, altering the approach to treating bacterial infections. Before its availability, even minor cuts or illnesses could lead to fatal outcomes, as physicians had few effective tools to combat bacteria. Its story is an example of scientific observation, chance, and the persistence required to turn a laboratory finding into a world-changing treatment.
The Serendipitous Discovery
The story of penicillin begins in September 1928 with Scottish bacteriologist Alexander Fleming. After returning to his London laboratory from a holiday, he noticed a petri dish growing Staphylococcus bacteria was contaminated with a blue-green mold, later identified as Penicillium notatum.
Fleming observed a clear, bacteria-free zone surrounding the mold and deduced it was producing a substance that inhibited bacterial growth. He called this “mould juice” and found it was lethal to a wide range of harmful bacteria after cultivating the mold in a liquid broth to test its properties.
He confirmed the substance’s antibacterial effects and found it was not toxic to human white blood cells. Fleming published his findings in 1929 but faced challenges in isolating the active agent. Because of these difficulties and the substance’s instability, the scientific community largely overlooked his discovery for more than a decade.
From Lab Curiosity to Lifesaving Medicine
The potential of Fleming’s discovery was not realized until the late 1930s at the University of Oxford. A team of researchers, led by Howard Florey and Ernst Chain, came across Fleming’s paper and took on the challenge of isolating the active compound. Their work was driven by the need for new treatments for bacterial infections as World War II began.
Chain devised a method to purify penicillin from the mold culture, resulting in a stable powder. This purified form was potent enough for animal testing, which proved its ability to protect mice from lethal streptococci infections. These successful trials gave the team the confidence to proceed with human testing.
The first human subject was a police constable, Albert Alexander, in 1941, who was dying from a severe infection. Within days of receiving penicillin, his condition improved. Unfortunately, the initial supply ran out, and he relapsed and died, highlighting the challenge of producing penicillin in large quantities. Recognizing its potential, Florey traveled to the United States to seek help with mass production, leading to a collaboration that enabled the drug’s widespread availability.
How Penicillin Works
Penicillin belongs to a class of antibiotics known as beta-lactams. Its function is bactericidal, meaning it directly kills bacteria by interfering with the bacterial cell wall. This rigid outer layer provides physical protection and prevents the cell from bursting.
The primary component of the bacterial cell wall is peptidoglycan. Penicillin works by blocking the enzymes bacteria use to link these molecules together. This inhibition prevents the bacteria from building and maintaining a stable cell wall.
As a bacterium grows, it cannot repair holes in its weakened cell wall. Internal pressure forces water to rush in, causing the cell to swell and rupture in a process called lysis. Because human cells lack cell walls, penicillin can target bacteria without harming the patient.