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Introduction to Microbiology Lesson 1 : Introduction,
Lesson 1 : Introduction,
history and definitions Microbiology
Microbiology …the study of simple forms of living
matter invisible to the naked eye •These life forms are called microorganisms or microbes. •They are so tiny that they can be seen and examined only through a microscope. •The modern science of microbiology began about one hundred years ago. •The word microbiology is derived from the Greek micros, meaning small, bios, meaning life, and logy, meaning the study of. The scientific method:
The scientific method:
•is the method of systematic study involving the rational organization of scientific information. •was largely responsible for the development of the science of microbiology. (The development of microbiology was associated primarily with improving the health of the human population and reducing the ravages of infectious diseases). • It’s only been in the past 75 to 100 years that many of our infectious diseases have been brought under control. Epidemic classics such as smallpox, typhus, cholera and plague were responsible for wiping out as much as one
fourth of the population of a small country. • Before 1900, childhood infections would kill as many as one half of the children born. Today the number of persons dying from infectious diseases is only a small portion of what it was in earlier times. • Developments that led to the control of many devastating human microbial diseases represent some of the great triumphs of modern technology. • However, many infectious diseases are still not effectively controlled. As social and physical living conditions change, new patterns of older diseases, as well as, entirely new diseases develop. Van Leeuwenhoek
•Microorganisms were discovered more than two hundred years before microbiology became a recognized science. •The discovery was made in 1687 by Anton van Leeuwenhoek who discovered tiny forms of life in a drop of water which he was examining through one of his magnifying lenses. Until then no one even knew that microorganisms existed. Van Van Leeuwenhoek’s microscope •Anton van Leeuwenhoek termed these tiny organisms ‘animalcules’ and recorded his observations with uncanny accuracy. He found these organisms in samples taken from all parts of the body and through the course of his discoveries, he made more than 250 microscopes. • Lazzaro Spallanzani was one of the first scientists to perform experiments using microorganisms. He proved that if dust and air were removed from a test tube containing microbes and then heated, the microbes would die. Once they died, no more would develop. •In 1796, a major contribution was made to microbiology when Edward Jenner developed a safe and efficient method to vaccinate against smallpox Louis Pasteur
•Louis Pasteur was a French scientist who is called the father of microbiology.
• He was the first to discover that bacteria are the cause of specific diseases in humans and animals. His ‘germ theory of disease’ paved the way for further advances in bacteriology and he later proved that bacteria could be destroyed by boiling or the process of sterilization.
• Pasteur developed a vaccine for preventing anthrax in sheep, and he perfected pasteurization, which is a method of destroying the lactic acid
forming bacteria that causes milk to sour. Robert Koch’s postulates
Robert Koch’s postulates
In 1882, Robert Koch discovered the bacterium Mycobacterium tuberculosis and developed the 4 postulates that prove a certain bacteria cause a disease:
Postulate #1: The same microbes are present in every case of the disease.
Postulate #2: The microbes are isolated from the tissues of a dead and a pure culture is prepared.
Postulate #3: Microbes from the pure culture are inoculated into a healthy animal. The disease is reproduced.
Postulate #4: The identical microbes are isolated and recultivated from the tissue specimens of the experimental animal. • In 1867, an English surgeon named Lord Joseph Lister introduced the antiseptic method into surgery which helped to reduce the number of postop infections after surgery. By using bandages and cloths soaked in carbolic acid, he was able to show that cross
contamination between patients could be minimized. • From these experiments proving that diseases could be prevented, chemical formulations were found that could prevent microbial growth and infection. It was from these experiments that the family of antibiotics that we use today arose. penicillin
• In 1928, penicillin was discovered by Sir Alexander Fleming. • He noticed that when the green mold Penicillium notatum was put into a culture dish, the waste products from the mold would inhibit growth of the culture. • It turned out that his discovery later saved his life when he made a dramatic recovery after being stricken by pneumonia. Antibiotic disks on a bacterialcolonized petri dish for determination of bacterial susceptibility to different forms of antibiotics vaccines
• Viruses were discovered in 1892 but suitable methods of culturing them were not developed until around 1931 when chicken embryos were used to detect and isolate many common viruses. • By 1949 it was possible to grow viruses in testtube cultures of living tissues. This led to the production of vaccines to combat viral diseases, like the intradermal polio vaccine developed by Dr Jonas Salk and the oral polio vaccine developed by Dr Albert Sabin. Bacteriophage viruses infecting an E. coli bacteria Preventing infection
Once the bacteria were discovered, scientists were able to make the connection between microorganisms that are harmless to humans and those that are pathogenic or harmful and disease causing. The body’s natural defenses can be broken down into 3 categories: Mechanical, chemical and physiologic. 1. Mechanical barrier the skin. Just by itself, it’s impervious to water, and without an open cut or wound, most bacteria cannot cause disease by just coming in contact with the skin.
2. Chemical barriers sweat and the fluids of the stomach. Chemicals contained within the sweat and the acidity of the gastric juices are capable of fighting infection and destroying bacteria. 3. The components of the immune system would be examples of physiologic barriers. The ability of phagocytes to engulf microorganisms and form antibodies are one way our own bodies fight infection and put up a line of defense for future attacks. The majority of microorganisms we come in contact with are harmless but a person with low physical resistance can be especially prone to invasion by pathogenic microbes. • Microorganisms can cause mild or severe disturbances in the human body. As health care professionals, we have the responsibility to do what we can to protect our patients as well as ourselves. • Practicing proper health care procedures and precautions can prevent the unwanted spread of infections and minimize crosscontamination. • Frequent handwashing, sterilizing instruments, disinfecting surfaces, disposing of contaminants properly and practicing universal precautions will help to prevent and control the spread of microorganisms. The end
Reading assignment: Textbook ‘Microbiology for the Health Sciences’ Chapter 1 Microbiology: The Science pp. 124 ...
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- Spring '05