Introduction Microbiology

Historical Introduction to Medical Microbiology

Dr. Deepak W. DeshkarDepartment of Microbiology D.Y.Patil Medical College, Kolhapur

Microbiology

Microbiology (from Greek μῑκρος, mīkros, "small"; βίος, bios, "life"; and -λογία, -logia) is the study of microorganisms, which are microscopic, unicellular, and cell-cluster organisms

Medical Microbiology is the study of microbes that infect humans, the diseases they cause, their diagnosis, prevention & treatment.

It also deals with the response of the human host to microbial and other antigens.

Microbes, or microorganisms are minute living things that are usually unable to be viewed with the naked eye.

What is Medical Microbiology?

Medical Microbiology

Why is it Important?

Infection is one of the most important causes of mortality and morbidity in the population.Approximately 30% of hospital patients are on antibiotics at any one time1 in 10 patients acquires an infection whilst in hospital.

Bacteria, fungi, protozoa, algae, viruses are examples!

Some are pathogenic

What are some examples of microbes?

Some organisms studies by microbiologists CAN be visualized without the aid of amplification [bread molds (fungus) and filamentous algae] These organisms are included in the discipline of

microbiology because of similarities in properties and techniques used to study them

Techniques necessary to isolate and culture microorganisms Isolation Sterilization Culture in artificial media

Microbiologists may be interested in specific types of organisms: Virologists - viruses Bacteriologists - bacteria Phycologists or Algologists - algae Mycologists - fungi Protozoologists - protozoa

Microbiologists may have a more applied focus: Medical microbiology, including immunology Food and dairy microbiology Public health microbiology Industrial microbiology Agricultural microbiology

Microbiologists may be interested in various characteristics or activities of microorganisms: Microbial morphology Microbial cytology Microbial physiology Microbial ecology Microbial genetics and molecular biology Microbial taxonomy

History of Microbiology

The existence of microorganisms was hypothesized for many centuries before their actual discovery. The existence of unseen microbiological life was postulated by Jainism which is based on Mahavira’s teachings as early as 6th century BCE.

Early Discoveries

Lucretius, a Roman philosopher (98-55 B.C.), and Girolamo Fracastoro, a physician (1478-1553) believed invisible creatures were responsible for disease

Franscesco Stelluti observed bees and weevils using a microscope in the early 1600s


Paul Dundas notes that Mahavira asserted existence of unseen microbiological creatures living in earth, water, air and fire. Jain scriptures also describe nigodas which are sub-microscopic creatures living in large clusters and having a very short life and are said to pervade each and every part of the universe, even in tissues of plants and flesh of animals


The Roman Marcus Terentius Varro made references to microbes when he warned against locating a homestead in the vicinity of swamps "because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases."

Concept of “Animalia minuta”



The first microbes were observed in 1673.

In 1665, Robert Hooke (Englishman) reported that living things were composed of little boxes or cells.


1673-1723, Antoni van Leeuwenhoek (Dutch) described live microorganisms that he observed in teeth scrapings, rain water, and peppercorn infusions.


Spontaneous Generation

The belief that life could originate from non-living or decomposing matter


Spontaneous Generation Supported by:

Aristotle (384-322 BC) – Believed that imple invertebrates could arise by spontaneous generation

John Needham (1713-1781) – Boiled mutton broth, then sealed and still observed growth after a period of time

Lazarro Spallanzani (1729-1799) No growth in sealed flask after boiling – proposed that air was needed for growth of organisms

Felix Pouchet (1859) – Proved growth without contamination from air


Spontaneous Generation Disproved by:

Francesco Redi (1626-1697) – maggot unable to grown on meat if meat was covered with gauze

Schwann, Friedrich Schroder and von Dusch (1830s) – Air allowed to enter flask but only after passing through a heated tube or sterile wool

John Tyndall (1820-1893) – Omission of dust no growth. Demonstrated heat resistant forms of bacteria (endospores)


Many believed spontaneous generation:

life can arise from non-living matter.

In 1668, the Italian physician Francesco Redi performed an experiment to disprove spontaneous generation.

Can you think of an experiment that could disprove spontaneous generation?

Redi filled six jars with decaying meat.


Conditions Results

3 jars covered with fine net No maggots

3 open jars Maggots appeared

From where did the maggots come?

What was the purpose of the sealed jars?

Spontaneous generation or biogenesis?

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-3Sealed No maggots developed


Rudolf Virchow (German) presented biogenesis: living cells can arise only from preexisting cells.


So now there are two hypotheses:

1. The hypothesis that living organisms arise from nonliving matter is called spontaneous generation. According to spontaneous generation, a “vital force’ Forms life.

2. The Alternative hypothesis, that the living organisms arise from preexisting life, is called biogenesis.


1861: Louis Pasteur demonstrated that microorganisms are present in the air.


Conditions Results

Nutrient broth placed in flask, heated, not sealed

Microbial growth

Nutrient broth placed in flask, heated, then sealed

No microbial growth

Spontaneous generation or biogenesis?

The Golden Age of Microbiology 1857-1914

Beginning with Pasteur’s work, discoveries included the relationship between microbes and disease, immunity, and antimicrobial drugs


Louis Pasteur (1822 - 1895)


Pasteur showed that microbes are responsible for fermentation.

Fermentation is the conversation of sugar to alcohol to make beer and wine.

Microbial growth is also responsible for spoilage of food.

Bacteria that use alcohol and produce acetic acid spoil wine by turning it to vinegar (acetic acid).


Pasteur demonstrated that these spoilage bacteria could be killed by heat that was not hot enough to evaporate the alcohol in wine. This application of a high heat for a short time is called pasteurization.

Louis Pasteur (1822 - 1895)

trapped airborne organisms in cotton;

he also heated the necks of flasks, drawing them out into long curves, sterilized the media, and left the flasks open to the air;

no growth was observed because dust particles carrying organisms did not reach the medium, instead they were trapped in the neck of the flask; if the necks were broken, dust would settle and the organisms would grow; in this way Pasteur disproved the theory of spontaneous generation


The 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 puerperal fever from one OB patient to another.



M. J. Berkeley (ca. 1845) demonstrated that the Great

Potato Blight of Ireland was caused by a Fungus



• 1860s: Joseph Lister used a chemical disinfectant to prevent surgical wound infections after looking at Pasteur’s work showing microbes are in the air, can spoil food, and cause animal diseases. Joseph Lister (1827 - 1912)

developed a system of surgery designed to prevent microorganisms from entering wounds – phenol sprayed in air around surgical incision

Decreased number of post-operative infections in patients his published findings (1867) transformed the practice of

surgery


The Germ Theory of DiseaseCharles Chamberland (1851 - 1908)

identified viruses as disease-causing agents – Tobacco Mosaic Virus

Edward Jenner (ca. 1798) used a vaccination procedure to protect individuals

from smallpox

Louis Pasteur developed other vaccines including those for chicken

cholera, anthrax, and rabies




1876: Robert Koch provided proof that a bacterium causes anthrax and provided the experimental steps, Koch’s postulates, used to prove that a specific microbe causes a specific disease.

Koch was a physician and Pasteur’s young rival

A young milkmaid informed the physician Edward Jenner that she could not get smallpox because she had already been sick from cowpox.

1796: Edward Jenner inoculated a person with cowpox virus. The person was then protected from smallpox. Called vaccination from vacca for cow

The protection is called immunity


Chemotherapy – treatment with chemicals

Chemotherapeutic agents used to treat infectious disease can be synthetic drugs or antibiotics.

Antibiotics are chemicals produced by bacteria and fungi that inhibit or kill other microbes.

Quinine from tree bark was long used to treat malaria.


Chemotherapy – treatment with chemicals

1910: Paul Ehrlich developed a synthetic arsenic drug, salvarsan, to treat syphilis.

1930s: Sulfonamides were synthesized.



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.

AngelinaAngelina Hesse Hesse

Development of Agar Used to Grow Microorganisms.

Although the microscope was invented in the 1600’s, it took 200 years for scientists to discover its use in isolating and identifying specific microbes for a particular disease.

Koch’s PostulatesThe specific causative agent must be found in every case of the disease.

The disease organism must be isolated from the lesions of the infected case and maintained in pure culture.

The pure culture, inoculated into a susceptible or experimental animal, should produce the symptoms of the disease.

The same bacterium should be re-isolated in pure culture from the intentionally infected animal.

The specific antibodies to the bacterium should be demonstrable in the serum of patients suffering from the disease.

Isolation of Important Bacteria in the Late 19th Century

1882 – Tubercle bacillus ( Koch)

1883 - Cholera Vibrio ( Koch )

1883 - Diphtheria Bacillus ( Klebs , Loeffler )

1886 - Pneumococcus ( Frankel)

1887 - Meningococcus ( Weichselbaum )

Thank you

Introduction Microbiology

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