Alexander Fleming and Penicillin: The Accidental Discovery?



Download 18,65 Kb.
Date conversion16.04.2017
Size18,65 Kb.

Alexander Fleming and Penicillin: The Accidental Discovery?

A Clinical Case

  • A 48 year old policeman presents to Urgent Care with a small cut on his face after shaving
  • The cut is slightly red and draining a small amount of pus
  • Before the 1940s this small, infected cut could lead to a swift death

The Discovery of Penicillin: One of the Most Important Events in Medical History

  • For the first time, doctors had a way to treat infections and miraculously save lives
  • Prior to the discovery of penicillin patients often died from trivial injuries or infections
  • Today in the United States, deaths by infectious bacterial diseases are one-twentieth what they were in 1900

Prior to Penicillin

  • Physicians had little ability to help patients suffering from infection

Physicians could only watch and wait hoping a patient’s immune system could topple an infection

  • The Doctor by Sir Luke Fildes

Fungus as Treatment

  • Folk remedies using fungi have been used for thousands of years
  • 3000 years ago, the Chinese were using moldy soybean curd on boils and other skin infections

Our story begins . . .

  • Alexander Fleming was born in Lochfield Scotland in 1881, the son of a pig farmer

Fleming’s Childhood

  • The seventh of eight children, Fleming received a very good education and was able to attend the University of London on scholarship

The Boer War

  • In 1900 the Boer War started between the UK and the colonies in Southern Africa
  • Fleming and his two brothers joined a Scottish regiment
  • They never saw a battlefield and instead spent lot of time swimming, shooting and playing water polo

Fleming gets an MD

  • Fleming was left money after his uncle died and his older brother (already an MD) recommended he go to medical school
  • Fleming got very high scores on his entrance exams and was able to choose from three medical schools
  • He chose St Mary’s in London because he had once played water polo against them

Water Polo?

  • Water polo was created in England during the 1860's because swimming was becoming a popular sport

Career Choices

  • Fleming graduated from medical school in 1906 at the age of 25
  • He was offered a job as research assistant at the inoculation department at St Mary’s Hospital in London not just for his medical background but also because he was a very good shot – his shooting skills would strengthen the hospital’s rifle team

St Mary’s Hospital

St Mary’s Hospital Lab

  • Fleming was working for Sir Almroth Wright who had discovered an anti-typhoid vaccine in 1896
  • Both Fleming and Wright went to France during WWI to treat wounded soldiers and saw firsthand there was no effective treatment for most infections

Fleming’s Personality

  • Unlike Wright who had an arrogant, forceful personality, Fleming was a shy man
  • Fleming also was a lackluster lecturer who was described by one student as “a shocking lecturer, the worst you could possibly imagine”
  • Nevertheless, Fleming inspired many by his future work

Treating Syphilis

  • Incidentally, St Mary’s was one of the first places salvarsan was used to treat syphilis
  • Fleming had published on this topic and was considered an expert at administrating salvarsan
  • If fact, Fleming made quite a bit of extra income treating members of the London Arts community for syphilis
  • Often, artists would give him paintings as payment for his services
  • Fleming’s background in administering salvarsan exposed him to the ill-effects of substances that interfere with natural host defense processes

The Discovery of Lysozyme

  • In 1922 Fleming described lysozyme
  • Lysozymes are enzymes present in diverse materials such as tears, mucous, egg whites etc that cause bacteria to lyse
  • His lysozyme research grew out of his interest in showing the ineffectiveness of chemical antiseptics to treat infection

Chemical Antiseptics

  • The idea of using chemical antiseptics to kill germs was a revolutionary idea of the late 19th century popularized by Joseph Lister
  • Lister was a Scottish surgeon, influenced by Pasteur, who believed that germs caused infection
  • Lister (1827-1912)

Lister continued . . .

  • In 1874 he developed the method of using carbolic acid to kill germs and prevent wound infections after surgery
  • Lister’s theories revolutionized surgery
  • Lister argued that antiseptics could also be used on wounds to kill bacteria

Fleming Disagrees

  • Based on Lister’s theory, physicians of the time generally believed that if antiseptics killed germs they were therefore useful in treating wound infections
  • Fleming strongly disagreed with this idea
  • Fleming and his mentor, Wright, argued that the best way to treat wound infections was to enhance the body’s natural immune response

A Revolutionary Approach to Wound Care

  • Fleming and Wright noted that, although antiseptics kill bacteria, they also kill leukocytes of the immune system more rapidly than they kill invading bacteria
  • They recommended using saline solution to cleanse wounds instead of antiseptic solutions

Lysozyme Research

  • Few accepted Wright and Fleming’s recommendation for wound care
  • This rejection fueled Fleming’s search for antibacterial agents and particularly his interest in lysozyme
  • Like leukocytes, lysozyme was an endogenous way to treat infections
  • Fleming believed that the best way to treat wound infections was to enhance the body’s natural immune response

Lysozyme continued

  • In 1922 Fleming described lysozyme when he noted that lysozyme-containing material would interfere with the growth of bacterial cultures
  • Fleming found that a culture of his own nasal mucous inhibited the growth of staph cultured from that same mucous

Lysozymes continued

  • Fleming was fortunate in that the strain of bacteria he was culturing was particularly sensitive to lysozyme
  • However, Fleming was disappointed in that the bacteria most susceptible to lysozyme were those that aren’t as infectious in humans

Making the Connections

  • Fleming’s background with lysozyme research prepared him for his next major discovery

Disorganization Leads to Genius

  • Fleming had a notoriously disorganized lab

Discovery . . .

  • In 1928 after returning to his lab following a two week vacation Fleming encountered the place in its usual disarray
  • Fleming had a inoculated a number of petri dishes with staphylococci prior to leaving on vacation
  • He hadn’t placed them in an incubator because he knew that the staph would sufficiently multiply over the long vacation
  • Little did he know that penicillium mold grows well at room temperature

Fleming’s observation

  • Fleming returned to his lab to find many of his culture plates contaminated with fungus
  • He immediately started preparing to clean all his plates but it happened that a former member of his lab was visiting that day
  • Fleming took some of the contaminated cultures to show his visitor and that’s when he noticed the inhibition zone around the fungus

Fleming’s Observation cont.

  • Fleming was not very knowledgeable about fungi but knew that the mold in his dish was a species of penicillin
  • Eventually determined to be Penicillium notatum

Accidental?

  • Fleming’s observation was made under some accidental circumstances but clearly made sense in light of Fleming’s research background
  • Fleming had the sophistication to realize that anti-bacterial agents existed – this view was really fueled by his background in lysozyme research

The Power of Penicillin

  • It was obvious to Fleming that penicillin was much more powerful than lysozymes because his crude extracts could be diluted 1000 times and still be effective in killing bacteria

1929 Paper

  • In 1929 Fleming published a paper detailing his discovery
  • This was also a crucial moment because his ideas reached a large audience
  • But it wasn’t until ten years later that other scientists began trying to use penicillin to treat clinical disease

1929-1931

  • Fleming continued to work on and off with penicillin during this time but was never able to produce it in quantities necessary for practical testing or applications
  • Fleming found that many of his cultures were unstable and stopped producing mold after eight days
  • Interestingly, Fleming initially conceived of penicillin as a topical agent and did not think of using it as an injectable or ingestible medication

Fleming’s Research

  • Fleming did inject one rabbit and one mouse with penicillin to make sure there were no ill effects (there were none) but never injected these animals with a simultaneous bacterial strain
  • Ironically, even though Fleming was an expert at administering intravenous salvarsan to syphilis patients, he only thought of penicillin as an external germicide
  • Fleming, in his 1929 article, compares penicillin’s effects to carbolic acid (anti-septic favored by Lister and his followers for treating wound infections)

Fleming Moves On

  • Fleming, when asked why he abandoned his initial research, noted that his preparations quickly lost their antibacterial effects
  • He lacked the help of a biochemist to assist him with penicillin extraction
  • Wright wouldn’t allow the presence of a biochemist is the lab because he thought chemists lacked humanism

Dr. Cecil Paine and “Mold Juice”

  • Paine - student of Fleming who was first to demonstrate the value of penicillin in medicine
  • After reading Fleming’s article, Paine obtained from Fleming a sample of the PCN mold, made cultures and used it to treat the lacerated eye of a local miner. The miner still had a piece of the stone in his eye with a severe pneumococcal infection
  • Paine irrigated the eye with crude PCN extract “mold juice” and the patient’s eye was saved
  • Paine also irrigated the eyes of a baby born to a mother with gonorrhea and saved the child’s eyes

The Players Assemble

  • Paine never published his results but did share them with Dr. Howard Florey at Oxford who became actively interested in penicillin in the 1930s
  • Coincidentally, a researcher at Oxford Ms. Campbell-Renton had some of Fleming’s original mold passed down to her from an old boss who had used it for some unsuccessful research
  • Dr Ernst Chain, a talented biochemist who fled Nazi Germany, persuaded by Dr. Florey to join his Oxford team

Florey and Chain

The Players Assemble, continued

  • Chain accidentally bumped into Cambell-Renton in the hall one day while she was carrying a flask of Fleming’s mold
  • Chain went to Florey with the idea to research biochemical and biological properties of antibacterial substances produced by microorganisms
  • Funding was obtained and research began

Florey, Chain continued

  • Soon after beginning his research, Chain discovered that penicillin was not an enzyme but a molecule
  • He was intrigued by the fact that penicillin was a very unstable molecule
  • Chain was able to freeze- dry the penicillin and produce a stable brown powder
  • Tested on mice, a huge dose proved safe

Florey, Chain continued

  • Another important observation was that the penicillin powder turned the mice’s urine brown – it passed unaltered and without loss of effects into the urine
  • This meant that PCN could pass through the body and fight infections wherever they were
  • The Oxford team was ecstatic about their discovery and began work immediately to prove their findings were correct

Experimental Testing

  • Florey next experimented with mice and lethal doses of streptococci
  • Eight mice were injected with the bacteria and only four mice received penicillin prior to the bacterial injection: the four “PCN mice” survived and the others all died
  • The first landmark paper detailing the mice experiments were published in August 1940

Timing

  • England was very close to jeopardy at this point in WWII and members of this Oxford team all rubbed penicillin mold on the inside of their clothing fearing that if Germany should invade and occupy Britain one might be able to escape to North America with mold spores!
  • They know that PCN had the potential to save millions of lives

Human Testing

  • After the researchers were confident that PCN was safe in mice they began human testing
  • 48 y/o policeman with bacterial sepsis after cutting himself while shaving improved dramatically after treatment with the PCN but he required such high doses that the supply was quickly gone
  • The researches even tried to recrystallize the PCN from this patient’s urine to give back to him but the patient didn’t survive

Human Testing Continued

  • The researchers continued but changed their patient focus to small children thinking they required less PCN for good outcomes
  • Almost all the children were miraculously cured of infection

Mass Production of Penicillin

  • Penicillin Production began in Britain on a small scale in 1941
  • The British government encouraged the development of a number of small production facilities at this time. Large scale companies could easily be bombed by German war planes.

Production in North America

  • Florey’s visited the US and Canada with a vial of the sample mold July 1941
  • It was recommended by an American professor that Florey meet with the head of the USDA research laboratory in Peoria, IL Dr. Robert Coghill
  • Coghill suggested deep fermentation would likely make the production of penicillin more efficient and convenient

Mass Production and Peoria

  • The search was on for even better sources for penicillin producing Penicillium
  • The best specimen was mold found on a cantaloupe purchased at a Peoria market
  • Penicillium chrysogenum

Production Accelerates

  • From January to May 1943 only 400 million units of penicillin had been made
  • By the time the war ended US companies were making 650 billion units a month!

Infections and World War

  • During WWI the death rate from pneumonia in the US Army totaled 18%
  • During WWII the death rate fell to less than 1%

Awards

  • Fleming and Florey were knighted in 1944
  • Chain was later knighted in 1965
  • The Nobel Prize in Physiology or Medicine was awarded to Fleming, Florey and Chain in 1945

Drug resistance

  • Although the discovery of penicillin is arguably one the greatest discoveries of humankind, drug resistance poses an enormous problem
  • In 1994, 13,300 patients died of drug-resistant bacterial infections

Modern Day Treatments

  • A 48 year old policeman presents to Urgent Care with a small cut on his face after shaving
  • Today: prescribe antibiotics


The database is protected by copyright ©sckool.org 2016
send message

    Main page