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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

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medical microbiology

Medical Microbiology

The History

EQ: Who are the major contributors to the development of Microbiology?

what is 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 are some of examples of microbes

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?

  • Not all bacteria cause disease
    • Most bacterial species cannot cause disease
  • When you hear the word bacteria, what comes to your mind?

Figure 1. Gram stain of a species of Micrococcus, commonly isolated from the skin and nasal membranes of humans. Figures from:


What is Microbiology?

  • 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 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 history1
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 history2
Ancient Microbiological History
  • The Romans understood that sewage could cause disease and there for 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
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
History of Microbiology: The Theories
  • Spontaneous Generation
  • Many believed in spontaneous generation:
    • Aristotlesynthesized 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.
spontaneous generation

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
spontaneous generation1

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.
spontaneous generation2

History of Microbiology: The Theories

Spontaneous Generation

The Question: What causes tiny living things to appear in decaying broth?

  • LazzaroSpallanzani (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

  • 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
settlement of spontaneous generation

History of Microbiology: The Theories

Settlement of Spontaneous Generation
  • In 1861, a French scientist by the name of Louis Pasteurdemonstrated 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

louis pasteur s swan neck flask experiment

History of Microbiology: The Theories

French chemist Louis Pasteur’s design of this experiment settled the argument. Click herefor an animation and quiz.

Louis Pasteur’s Swan neck flask experiment


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
Golden Age of Microbiology1857- 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 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
Germ Theory of Disease
  • 1835: AgostinoBassi- showed a silkworm diseases was caused by a fungus
  • 1865: Pasteur- believed that another silkworm disease was caused by a protozoan
  • 1840s: IgnazSemmelwise- advocated hand washing to prevent transmission of fever from one OB patient to another

germ theory of disease1
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
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.
koch s postulates

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
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
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 vaccine1
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
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
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
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.