Penicillin was the first antibiotic, and is still, 60 years after its first use, one of the most widely used of the drugs.
Prior to the development of penicillin, the treatment of bacterial infection was difficult or impossible. One of the most common treatments was to open the infection to allow the pus to drain. Advanced infections that could not be treated in this way, such as brain infections, would inevitably result in the death of the patient. Several bacterial infections could be treated in other ways, such as with infection specific drugs, but such treatment was often expensive, had unacceptable side effects, or relied on a definitive diagnosis.
The possibilities of antibiotics arose when Alexander Fleming, a British doctor, was examining some bacterial cultures he was about to dispose of. He noticed that, quite by chance, some mold had grown on one of his culture plates, and the bacteria on the plate failed to colonize the same area. The mold was quickly identified as penicillium.
However, how effective the mold could be was a matter of some contention. The mold itself is also fatal to human beings. Fleming himself thought that the substance would be little more than an antiseptic preparation for use in surgery. However, the active ingredient in the mold, soon dubbed penicillin, was found to still be effective in human patients even though the preparation was only about 3% pure. Moreover, the impurities had no toxic effect on patients.
Even then, it was doubtful that the mold could be grown in sufficient quantities to be useful as a pharmaceutical. Penicillium will only grown in the presence of oxygen, so it only grew on the surface of cultures. Moreover, a large amount of the mold had to be processed to obtain a small amount of the pharmaceutical. Despite these problems, the initial clinical trials were extremely successful, with terminal patients literally being brought back to life after treatment.
Thanks to the effort of an American team, a process was developed using corn liquor, a by-product of corn production, and aeration vessels to grow mass quantities of the mold. Fleming and the American team were eventually awarded the Nobel Prize in Medicine for his work. Today, penicillin is so inexpensive to produce that a supply good for several weeks only costs a few dollars.
One of the benefits of penicillin and other antibiotics is that they act on so wide a range of bacterial diseases and have such mild side effects in most patients that patients can be treated without a definitive diagnosis. However, some patients are allergic to penicillin, and other antibiotics must be used on such patients. Moreover, some bacteria are either immune to penicillin or have become resistant to it. In such cases, other antibiotics must be prescribed.
Penicillin works by attaching itself to the middle of bacteria as they divide, preventing them from forming a new cell wall. Instead, the bacterial cell just bursts. Penicillin resistant bacteria have evolved mechanisms to prevent penicillin molecules from attaching themselves.