Antibiotics are one of the common drugs prescribed by doctors. Antibiotics are chemical substances which kill or inhibit growth of microorganisms. Antibiotics have played a vital role in increasing the life expectancy of man. One of the first antibiotics to be effective against bacterial infections is penicillin. Penicillin is extensively used today and is almost a synonym for antibiotics. The Nobel Prize in medicine and physiology in 1945 was awarded to Sir Alexander Fleming, Ernst Boris Chain and Sir Howard Walter Florey “for the discovery of penicillin and its curative effect in various infectious diseases”.

In 1928, Sir Alexander Fleming was working on a bacteria known as staphylococcus. while sorting his petridishes, he observed that the growth of a fungal contaminant had inhibited the growth of staphylococci. He grew a pure culture of this fungal contaminant and identified it to be penicillium mold. When this mold was cultured in a broth for a week, the liquid extract from the broth was effective in preventing the growth of staphylococci even after diluting it by 500-800 times. He then continued and classified bacteria into penicillin sensitive, if they were killed, and penicillin insensitive, if they were not killed/inhibited by it. When he injected  penicillin into mice, it cured the mice of staphylococcus infection but the important thing was that it was harmless to mice, unlike the previous antibiotics that were discovered before penicillin.

Eventually, scientists had tried purifying penicillin in its purest form but failed until 1938. It was eventually purified by Ernst Chain and Howard Florey at the University Of Oxford and they also elucidated the structure of penicillin. After purification, Penicillin was active at a dilution of 1 in million. Although, they thought it to be pure subsequent experiments showed that it was not completely pure. They had also conducted experiments in mice, with the above purified compound and confirmed its curative role. In its purest form, its activity increases further by 40 times. In 1941, Albert Alexander was the first patient to receive the penicillin antibiotic. Eventhough, it improved the patients condition, he died as they ran out of penicillin.  Florey was also instrumental in persuading authorities in US for large scale commercial production of penicillin.