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Alexander Fleming and Penicillin:
The Accidental Discovery?
By Joanna Martin
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 onetwentieth what they were in 1900
Prior to Penicillin
• Physicians had little
ability to help patients
suffering from
infection
•The Doctor by Sir Luke Fildes
Physicians could only watch and wait hoping a patient’s
immune system could topple an infection
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 antityphoid 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 CambellRenton 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 freezedry 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 drugresistant 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