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Penicillin Defined:
Any of a group of broad-spectrum antibiotic drugs obtained from penicillium molds or produced synthetically, most active against gram-positive bacteria and used in the treatment of various infections and diseases.


Penicillin is one of the first and still widely used antibiotics. The discovery of Penicillin was by Alexander Fleming in 1928 at the St. Mary's Hospital. The discovery happened when Fleming observed a contaminated petri mould that let out a substance that killed the bacteria in the petri mould. Tests after tests, Fleming was now able to separate the juice from the mould and it was then named Penicillin. His discovery of penicillin was a breakthrough. It was able to destroy gonorrhea, meningitis, diphtheria and pneumonia bacteria. This was also safe for humans to take. But the new medicine was soon rejected. The medical community was determined that once bacteria entered a body, nothing could be done.


Alexander Fleming

Early penicillin culture facility at the Sir William Dunn School of Pathology, Oxford, England. © Museum of the History of Science, Oxford

Alexander Fleming at Work Courtesy, St. Mary's Medical School Hospital, London

It was not until WW2 that the penicillin was brought back to life. Howard Florey and Ernst Chain and their researchers picked up Fleming's work where he had left off. After months of work, they found a way to purify the medicine. They soon after injected the medicine in live mice. In a controlled experiment, they injected the mice with virulent streptococci. They found it cured mice with the bacterial infections while the other mice died. They soon went on to try it on a few human subjects received great results. Howard and Chain's team later developed penicillin in a powdered form. The medicine was on high demand and was on production for the war. At first, production in England was hard and expensive. So the manufacturing ended up in the United States where they also entered the war. By the middle of the war, penicillin was in full use in the war. And its aid on the war proved to be successful until the end.
refrigeration unit
Photograph courtesy of Merck Archives, ©Merck & Co. Inc.

Refrigeration equipment for large fermentation unit at Cherokee Plant, Danville, PA.
fermentation unit
Photograph courtesy of Merck Archives, ©Merck & Co. Inc.

Fermentation unit used in purifying penicillin in 1945.
upper part of fermentation unit
Photograph courtesy of Merck Archives, ©Merck & Co. Inc.

Upper part of fermentors (tanks) used to produce penicillin and vitamin B12.
The properties of the penicillin is the potassium salt of phenoxymethylpenicilin, provides the advantages of stability in an acidic medium and easy absorption when ingested.

Penicillin interferes bacteria by with synthesizing the cell wall. An enzyme known as transpeptidase is inactivated by cross linking of bacterial cell walls and accepts it as a substrate.Then a nucleophilic oxygen of the enzyme renders it inactive.The cell wall construction stops and the bacteria soon die as seen on this picture.

Among the bacteria sensitive to penicillin are those that cause infections, pneumonia, diphtheria, syphilis, and gonorrhea. The side effects of penicillin are allergic or hypersensitivity reactions, including skin rashes, hives, swelling, and anaphylaxis, or allergic shock. Most other infections , however, are treated by injections.
The diagram below shows that the penicillin is not a cingle compound, Instead all compounds are related with the same basic ring-like structure (beta-lactam) from two amino acids (valine and cystine)via a tripeptide intermediate. The third amino acid of the tripeptide is replaced by and acyl group (R) and the nature of this acyl group confers specific properties on different types of penicillin.

Picture A is a central colony of the Penicillium notatum grown for 5-6 days and was later overlaid with a thin film containing cells of the yellow bacterium Micrococcus luteus. The fungus has created a zone of growth inhibition of the bacterium. This typical asexual sporing structures of a species of Penicillium. Spores are produced in chains from flask-shaped cells (phialides) that are found at the tips of a brush-like aerial structure shown below on the picture B.


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