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Medical Microbiology
The History
EQ: Who are the major contributors
to the development of Microbiology?
What is Microbiology?
They study of microbes or microorganisms
Microbes, or microorganisms are minute living
things that are usually unable to be viewed
with the naked eye.
What is Microbiology?
What are some of examples of microbes?
Bacteria, fungi, protozoa, algae,
viruses, and some are parasites
(helminths)
Some are pathogenic
What is Microbiology?
Microbes
When you hear the word bacteria, what
comes to your mind?
Not all bacteria cause disease
Most bacterial species cannot cause disease
Figure 1. Gram stain of a species of Micrococcus, commonly
isolated from the skin and nasal membranes of humans. Figures
from: http://textbookofbacteriology.net/normalflora.html
What is Microbiology?
Microbes
Can microorganisms be good for us,
beneficial? Explain your answer
Many species play beneficial roles
Production of antibiotics and foodstuffs
Decompose organic waste
Produce industrial chemicals such as ethyl alcohol
and acetone
Produce fermented foods such as vinegar, cheese,
and bread
Ancient Microbiological
History
Ancient people recognized many
factors involved in diseases.
Most ancient people documented
that some diseases are
communicable
Example: When Black Death struck
Europe entire villages were
abandoned in an effort to escape
the highly infectious plague (1347
A.D)
No medical knowledge existed in
Medieval England to cope with the
disease.
Ancient Microbiological History
The Romans were a hygienic bunch and were concerned with
health and cleanliness (waste and sewage).
The Romans invented the first underground sewage system
Ancient Microbiological History
The Romans understood that sewage could cause disease
therefore decided to build an underground sewage system
which is an idea we still use today.
A network of pipes brought clean water into the city of Rome and removed
waste.
Waste flushed from the latrines flowed through a central channel into the
main sewage system and thence into a nearby river or stream.
The public bath houses was the place where people went to
socialize and do business as well as getting clean.
History of Microbiology?
Discovering organisms
First microbes were observed in 1673
Robert Hooke- In 1665 reported that living things were composed of
little boxes or cells
devised the compound microscope and illumination system
Antoni van Leeuwenhoek- (1673-1723)
He is considered the father of bacteriology
Made simple microscopes and began observing with them (1674)
Discovered bacteria (he called them animalcules)
Leeuwenhoek's microscope consisted simply of:
A) a screw for adjusting the height of the object being
examined
B) a metal plate serving as the body
C) a skewer to impale the object and rotate it
D) the lens itself, which was spherical
History of Microbiology: The
Theories
Spontaneous Generation
Many believed in spontaneous generation:
Aristotle synthesized the hypothesis which stated that some vital
force contained in given organic matter can create living
organisms from inanimate objects.
In basic terms spontaneous generation stated that living
organisms arise from non living matter.
History of Microbiology: The Theories
Spontaneous Generation
Spontaneous generation was disproved in 1668 by Italian
Scientist, Francesco Redi.
What are the steps to the scientific method?
If your were Francesco Redi, what experimental design would
you create to disprove spontaneous generation?
Redi’s Experiment:
Redi’s question: Where do maggots come from?
Hypothesized: Redi suspected that flies landing on the meat laid
eggs that eventually grew into maggots
Experiment: Placed meat in three separate jars
History of Microbiology: The Theories
Disproving Spontaneous Generation:
Redi’s Experiment
Jar #1
•
•
•
Left open
Maggots developed
Flies were observed
laying eggs on the
meat in the open jar
Jar #2
•
•
•
Covered with netting
Maggots appeared on
the netting
Flies were observed
laying eggs on the
netting
Jar #3
•
•
Sealed
No maggots
developed
History of Microbiology: The Theories
Spontaneous Generation
The Question: What causes tiny living things to appear in decaying
broth?
John Needham- revived the theory of spontaneous
generation in 1745
Needham theorized that if he took chicken broth and heated
it, all living things in it would die.
After heating some broth, he let a flask cool and sit at a
constant temperature. The development of a thick turbid
solution of microorganisms in the flask was strong proof to
Needham of the existence of spontaneous generation.
History of Microbiology: The Theories
Spontaneous Generation
The Question: What causes tiny living things
to appear in decaying broth?
Lazzaro Spallanzani (1729-1799)
In 1776 he demonstrated that microorganisms
were already in the solution, the container, or
the air
He took solutions which he knew would
"breed" organisms and boiled them for up to
an hour. The flasks were hermetically sealed to
keep out contaminated air.
History of Microbiology: The Theories
Biogenesis
In 1858 German scientist, Rudolf
Virchow challenged spontaneous
generation with his concept of
biogenesis
Living organisms arise from preexisting life
Virchow presented his idea to the
scientific community, but could not
back it up with a convincing
experiment
History of Microbiology: The Theories
Settlement of Spontaneous Generation
In 1861, a French scientist by
the name of Louis Pasteur
demonstrated where
microorganisms came from
Father of Medical Microbiology
Demonstrated the microorganisms
exist in the air and could
contaminate sterile solutions by
passing air through cotton filters
The filter trapped tiny particles
floating in the air
http://www.microbiologytext.com/index.php?module=Book&func=displayarticle&art_id=27
History of Microbiology: The Theories
Louis Pasteur’s Swan neck flask
experiment
http://www.microbiologytext.com/index.php?module=Book&func=displayarticle&art_id=27
French
chemist
Louis
Pasteur’s
design of
this experiment settled
the argument.
History of Microbiology: The Theories
Louis Pasteur’s experiments
Louis Pasteur performed numerous experiments to
discover why wine and dairy products became sour
He found that bacteria were to blame (lactic acid fermentation)
Pasteur called attention to the importance of microorganisms
in everyday life and stirred scientists to think that if bacteria
could make the wine “sick,” then perhaps they could cause
human illness.
Golden Age of Microbiology
18571914 included the relationship
Beginning with Pasteur’s work,
discoveries
between microbes and disease, immunity and antimicrobial medicine
Germ Theory of Disease
Germ theory states that specific
microscopic organisms are the cause of
specific diseases.
Pasteur and The Germ Theory of
Disease
Pasteur showed that microbes are
responsible for fermentation
Microbial growth is also responsible for
spoilage of food
Pasteur demonstrated that spoilage bacteria
could be killed with heat (pasteurization)
Discovered that weak forms of disease could
be used as an immunization against stronger
forms and that rabies was transmitted by
viruses too small to be seen under the
microscopes of the time
Developed vaccines for anthrax (1881)and
rabies (1885)
Germ Theory of Disease
1835: Agostino Bassi- showed a silkworm
disease was caused by a fungus
1865: Pasteur- believed that another silkworm
disease was caused by a protozoan
1840s: Ignaz Semmelwise- advocated hand
washing to prevent transmission of fever from
one OB patient to another
http://www.youtube.com/watch?v=KSLCkT2ttXQ
Germ Theory of Disease
1860s: Joseph Lister- He is the father of
antiseptic surgery.
He used a chemical disinfectant (carbolic acid)
to prevent surgical wound infections after
reading Pasteur’s work showing microbes are
in the air, can spoil food, and cause animal
disease.
The Germ Theory of Disease:
Robert Koch
1867: Robert Koch- provided proof that
bacterium causes anthrax and provided
the experimental steps, Koch’s postulates,
used to prove that a specific microbe
causes a specific disease.
Germ Theory of Disease
Koch’s Postulates
Pathogen must be
present in all cases of
disease
Pathogen must be
isolated and grown in lab
in pure culture
Pathogen from pure
cultures must cause
disease when inoculated
into healthy, susceptible
lab animal
Same pathogen must be
isolated from the
diseased lab animal
Immunology: History of Vaccination
A precursor of smallpox vaccination was variolation
(The Germ Theory of Disease was not known at this time)
An early Asian method which introduced dried scabs of
smallpox patients and was later modified in Europe
Modification consisted of injecting infectious material under the skin
First tested among abandoned children and prisoners
When it was declared safe, members of the English royal family were
inoculated
Smallpox vaccine
1796: Edward Jenner is credited with the development
of the smallpox vaccine
Folk wisdom suggested that dairy maids who had
contracted cowpox seemed to be immune to smallpox
Infection with the cowpox virus produced a much less
severe form of disease than smallpox
Smallpox Vaccine:
Jenner conducted an
experiment in which he used
scabs from the cowpox lesions
on the arm of a dairy maid,
Sarah Nelmes to create a
small pox vaccine
He then used the material to
vaccinate an 8 year old boy,
James Phipps
After being vaccinated Phipps
appeared to develop immunity to
the smallpox virus.
Smallpox vaccine continued
Later Jenner vaccinated his own son and several other
children
He obtained similar results
Worldwide elimination of smallpox was achieved in 1978
Called vaccination from vacca for cow
The protection is called immunity
Discovery of Penicillin
1928: Alexander Fleming
discovered the first antibiotic.
He observed that Penicillium
fungus made an antibiotic,
penicillin, that killed S. aureus.
1940s: Penicillin was tested
clinically and mass produced and
was available towards the end of
World War II
Development of Agar
Angelina Hesse developed the use of Agar to grow
microorganisms.
She was the wife of Walter Hesse who worked in Koch’s
laboratory
Advantages of agar- It was not attacked by most bacteria.
Agar is better than gelatin because of its higher melting point
(96°c) and solidifying (40–45°c) points.