Infectious Diseases - Timeline

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  • Infectious Diseases: Timeline
  • Edward Jenner and vaccination
  • Ignaz Semmelweiss and the spread of infection
  • Louis Pasteur and the germ theory of disease
  • Joseph Lister and antiseptic surgery
  • Alexander Fleming and the discovery of penicillin
  • Recent Events
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Alexander Fleming and the discovery of penicillin

Alexander Fleming was looking for ways to destroy bacteria. In 1928, he was growing lots of bacteria known as staphylococci on agar plates. Alexander Fleming could be a bit slapdash - his lab was rather untidy, and he sometimes left the lids off his plates for a long time, letting the air in. Before going on holiday in 1928 Alexander made two mistakes. He didn't put all of his plates in bleach to sterilise them, and he left the lab windows open. When he came back from a holiday, Alexander noticed that lots of his culture plates were mouldy.

A common mould that might have grown happily on a slice of bread had landed on Alexander Fleming's plates – a stroke of luck which has saved millions of lives

Alexander Fleming

Although Florey and Chain developed it as a medicine, Fleming and his mouldy plates will always be remembered

Just before he put all the plates in the washing up to get clean, Fleming noticed something. Although lots of bacteria were growing on his plates, there was a clear ring in the jelly around some of the spots of mould – no bacteria were growing Something had killed the bacteria that was covering the jelly. Straight away Fleming saw that this might be important. He labelled and saved the plates.

Fleming worked hard on his mould, Penicillium notatum. He squeezed out some 'mould juice' which he called penicillin. But he couldn't get much penicillin from the mould. It wouldn't keep - even in the fridge - and he couldn't prove it would actually kill bacteria and make people better. By 1934 Fleming gave up on penicillin and went on to do different work!

In 1938 Howard Florey and Ernst Chain at Oxford University decided to do some work on penicillin. They infected eight mice with bacteria which would normally kill them. Four were given penicillin. The four treated mice stayed healthy – but the other four died.

They went on to treat Albert Alexander, a 43 year old policeman dying of a blood infection. Florey and Chain gave him penicillin for five days, and Albert was well on the way to health again when the penicillin ran out. Florey and Chain tried everything – they even collected spare penicillin from Albert's urine - but the infection came back and Albert died. Florey and Chain didn't give up. They collected more penicillin and used it on a 15 year old boy who had an infection after an operation. He was completely cured.

They showed the value of penicillin in destroying bacteria. The next problem was making enough of it to supply the demand of the soldiers in World War 2. In Britain all the big laboratories and factories were busy with the war effort. But Howard Florey knew lots of people in America, so the scientists took their mould to the United States where some of the big chemical companies helped them make penicillin on a large scale. Penicillin became available to everyone and the history of infectious diseases changed for ever.

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Medicine that acts against bacterial infections. Penicillin is an example of an antibiotic.
Protein that is produced by lymphocytes (white blood cells) and that attaches to a specific antigen.
Molecule on the surface of a pathogen that identifies it as a foreign invader to the immune system.
Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus.
The use of biological organisms or enzymes to create, break down or transform a material
To cut apart, or separate, tissue especially for anatomical study.
Exponential growth
If something is growing exponentially the larger the quantity gets, the faster it grows
Micro-organism that can grow in long tubes called hyphae or as single cells. Fungi have a nucleus, cytoplasm and a cell wall.
Herd immunity
If a high percentage of a population is immune to a disease the disease cannot be passed on because it cannot find new hosts.
Infection caused by the human immunodeficiency virus (HIV). It attacks and destroys the immune system.
Hybridoma cells are formed by fusing a specific antibody-producing cell with a type of cancer cell that grows well in tissue culture
Immune system
The body's natural defence mechanism against infectious diseases.
A process which gives immune resistance to a particular disease. The human or animal is exposed to a harmless antigen in order to raise antibodies and provide an immune memory.
A type of white blood cell that make antibodies to fight off infections.
A type of white blood cell that consumes dead pathogens that have been killed by antibodies.
Organism that feeds off another living host and causes it some damage. An example of a parasite is a tapeworm that lives in the digestive system of a host organism.
A micro-organism that causes disease.
Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.
A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.
Protozoa are one-celled animals
A spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavourable conditions.
A poisonous or toxic substance - produced by pathogens.
A small amount of dead or weakened pathogen is introduced into the body. It prepares the immune system to prevent future infections with the live pathogen.
Medicine that contains a dead or weakened pathogen. It stimulates the immune system so that the vaccinated person has an immunity against that particular disease.
The smallest of living organisms. Viruses are made up of a ball of protein that contains a small amount of the virus DNA. They can only reproduce after they have infected a host cell.
World Health Organization.
Chlorinated Lime
A mixture of calcium hydroxide, calcium chloride and calcium hypochlorite.
Free of pathogens. An aseptic technique is one performed under sterile conditions.
A chemical which can destroy microorganisms. Antiseptics are applied to the surface of the skin or to living tissue to reduce the possibility of infection.