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?
Microbres
 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 pre-existing 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
1857- 1914
 Beginning with Pasteur’s work, discoveries included the
relationship 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 diseases 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.